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The Grails Framework - Reference Documentation
Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown Version: 1.3.4 Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
Table of Contents
1. Introduction ................................................................................................................................................................ 6 2. Getting Started ............................................................................................................................................................ 7 2.1 Downloading and Installing .................................................................................................................................. 7 2.2 Upgrading from previous versions of Grails ......................................................................................................... 7 2.3 Creating an Application ....................................................................................................................................... 10 2.4 A Hello World Example ...................................................................................................................................... 11 2.5 Getting Set-up in an IDE ..................................................................................................................................... 11 2.6 Convention over Configuration ........................................................................................................................... 12 2.7 Running an Application ....................................................................................................................................... 12 2.8 Testing an Application ........................................................................................................................................ 13 2.9 Deploying an Application .................................................................................................................................... 13 2.10 Supported Java EE Containers .......................................................................................................................... 13 2.11 Generating an Application ................................................................................................................................. 14 2.12 Creating Artefacts .............................................................................................................................................. 14 3. Configuration ............................................................................................................................................................ 15 3.1 Basic Configuration ............................................................................................................................................. 15 3.1.1 Built in options .............................................................................................................................................. 15 3.1.2 Logging .......................................................................................................................................................... 16 3.1.3 GORM ........................................................................................................................................................... 18 3.2 Environments ....................................................................................................................................................... 19 3.3 The DataSource ................................................................................................................................................... 20 3.3.1 DataSources and Environments ..................................................................................................................... 21 3.3.2 JNDI DataSources ......................................................................................................................................... 22 3.3.3 Automatic Database Migration ...................................................................................................................... 22 3.3.4 Transaction-aware DataSource Proxy ........................................................................................................... 23 3.4 Externalized Configuration ................................................................................................................................. 23 3.5 Versioning ........................................................................................................................................................... 24 3.6 Project Documentation ........................................................................................................................................ 24 3.7 Dependency Resolution ....................................................................................................................................... 28 3.7.1 Configurations and Dependencies ................................................................................................................. 29 3.7.2 Dependency Repositories .............................................................................................................................. 29 3.7.3 Debugging Resolution ................................................................................................................................... 31 3.7.4 Inherited Dependencies ................................................................................................................................. 31 3.7.5 Providing Default Dependencies ................................................................................................................... 31 3.7.6 Dependency Reports ...................................................................................................................................... 31 3.7.7 Plugin JAR Dependencies ............................................................................................................................. 32 3.7.8 Maven Integration .......................................................................................................................................... 32 3.7.9 Deploying to a Maven Repository ................................................................................................................. 33 3.7.10 Plugin Dependencies ................................................................................................................................... 34 4. The Command Line .................................................................................................................................................. 36 4.1 Creating Gant Scripts .......................................................................................................................................... 36 4.2 Re-using Grails scripts ........................................................................................................................................ 37 4.3 Hooking into Events ............................................................................................................................................ 39 4.4 Customising the build .......................................................................................................................................... 41 4.5 Ant and Maven .................................................................................................................................................... 42 5. Object Relational Mapping (GORM) ....................................................................................................................... 47 5.1 Quick Start Guide ................................................................................................................................................ 47 5.1.1 Basic CRUD .................................................................................................................................................. 47 5.2 Domain Modelling in GORM ............................................................................................................................. 48 5.2.1 Association in GORM ................................................................................................................................... 49 126.96.36.199 One-to-one ............................................................................................................................................... 49 22.214.171.124 One-to-many ............................................................................................................................................ 50
126.96.36.199 Many-to-many ......................................................................................................................................... 51 188.8.131.52 Basic Collection Types ............................................................................................................................ 52 5.2.2 Composition in GORM ................................................................................................................................. 53 5.2.3 Inheritance in GORM .................................................................................................................................... 53 5.2.4 Sets, Lists and Maps ...................................................................................................................................... 54 5.3 Persistence Basics ................................................................................................................................................ 56 5.3.1 Saving and Updating ..................................................................................................................................... 56 5.3.2 Deleting Objects ............................................................................................................................................ 57 5.3.3 Understanding Cascading Updates and Deletes ............................................................................................ 57 5.3.4 Eager and Lazy Fetching ............................................................................................................................... 59 5.3.5 Pessimistic and Optimistic Locking .............................................................................................................. 60 5.3.6 Modification Checking .................................................................................................................................. 61 5.4 Querying with GORM ......................................................................................................................................... 62 5.4.1 Dynamic Finders ............................................................................................................................................ 63 5.4.2 Criteria ........................................................................................................................................................... 65 5.4.3 Hibernate Query Language (HQL) ................................................................................................................ 68 5.5 Advanced GORM Features ................................................................................................................................. 69 5.5.1 Events and Auto Timestamping .................................................................................................................... 69 5.5.2 Custom ORM Mapping ................................................................................................................................. 73 22.214.171.124 Table and Column Names ........................................................................................................................ 73 126.96.36.199 Caching Strategy ...................................................................................................................................... 76 188.8.131.52 Inheritance Strategies ............................................................................................................................... 78 188.8.131.52 Custom Database Identity ........................................................................................................................ 78 188.8.131.52 Composite Primary Keys ......................................................................................................................... 79 126.96.36.199 Database Indices ...................................................................................................................................... 79 188.8.131.52 Optimistic Locking and Versioning ......................................................................................................... 79 220.127.116.11 Eager and Lazy Fetching ......................................................................................................................... 80 184.108.40.206 Custom Cascade Behaviour ..................................................................................................................... 82 126.96.36.199 Custom Hibernate Types ....................................................................................................................... 82 22.214.171.124 Derived Properties ................................................................................................................................. 84 220.127.116.11 Custom Naming Strategy ....................................................................................................................... 85 5.5.3 Default Sort Order ......................................................................................................................................... 86 5.6 Programmatic Transactions ................................................................................................................................. 86 5.7 GORM and Constraints ....................................................................................................................................... 87 6. The Web Layer ......................................................................................................................................................... 90 6.1 Controllers ........................................................................................................................................................... 90 6.1.1 Understanding Controllers and Actions ........................................................................................................ 90 6.1.2 Controllers and Scopes .................................................................................................................................. 91 6.1.3 Models and Views ......................................................................................................................................... 91 6.1.4 Redirects and Chaining .................................................................................................................................. 94 6.1.5 Controller Interceptors ................................................................................................................................... 95 6.1.6 Data Binding .................................................................................................................................................. 97 6.1.7 XML and JSON Responses ......................................................................................................................... 101 6.1.8 More on JSONBuilder ................................................................................................................................. 103 6.1.9 Uploading Files ............................................................................................................................................ 105 6.1.10 Command Objects ..................................................................................................................................... 106 6.1.11 Handling Duplicate Form Submissions ..................................................................................................... 107 6.1.12 Simple Type Converters ............................................................................................................................ 108 6.2 Groovy Server Pages ......................................................................................................................................... 108 6.2.1 GSP Basics .................................................................................................................................................. 109 22.214.171.124 Variables and Scopes ............................................................................................................................. 109 188.8.131.52 Logic and Iteration ................................................................................................................................. 109 188.8.131.52 Page Directives ...................................................................................................................................... 110 126.96.36.199 Expressions ............................................................................................................................................ 110 6.2.2 GSP Tags ..................................................................................................................................................... 111 18.104.22.168 Variables and Scopes ............................................................................................................................. 111 22.214.171.124 Logic and Iteration ................................................................................................................................. 112 22.214.171.124 Search and Filtering ............................................................................................................................... 112 18.104.22.168 Links and Resources .............................................................................................................................. 113 188.8.131.52 Forms and Fields .................................................................................................................................... 113 188.8.131.52 Tags as Method Calls ............................................................................................................................. 114 6.2.3 Views and Templates ................................................................................................................................... 114 6.2.4 Layouts with Sitemesh ................................................................................................................................. 116 6.2.5 Sitemesh Content Blocks ............................................................................................................................. 118 6.2.6 Making Changes to a Deployed Application ............................................................................................... 119
6.3 Tag Libraries ..................................................................................................................................................... 119 6.3.1 Variables and Scopes ................................................................................................................................... 120 6.3.2 Simple Tags ................................................................................................................................................. 120 6.3.3 Logical Tags ................................................................................................................................................ 121 6.3.4 Iterative Tags ............................................................................................................................................... 121 6.3.5 Tag Namespaces .......................................................................................................................................... 122 6.3.6 Using JSP Tag Libraries .............................................................................................................................. 123 6.3.7 Tag return value ........................................................................................................................................... 123 6.4 URL Mappings .................................................................................................................................................. 123 6.4.1 Mapping to Controllers and Actions ........................................................................................................... 124 6.4.2 Embedded Variables .................................................................................................................................... 124 6.4.3 Mapping to Views ....................................................................................................................................... 126 6.4.4 Mapping to Response Codes ....................................................................................................................... 126 6.4.5 Mapping to HTTP methods ......................................................................................................................... 127 6.4.6 Mapping Wildcards ..................................................................................................................................... 127 6.4.7 Automatic Link Re-Writing ......................................................................................................................... 128 6.4.8 Applying Constraints ................................................................................................................................... 129 6.4.9 Named URL Mappings ................................................................................................................................ 129 6.5 Web Flow .......................................................................................................................................................... 131 6.5.1 Start and End States ..................................................................................................................................... 131 6.5.2 Action States and View States ..................................................................................................................... 131 6.5.3 Flow Execution Events ................................................................................................................................ 133 6.5.4 Flow Scopes ................................................................................................................................................. 134 6.5.5 Data Binding and Validation ....................................................................................................................... 135 6.5.6 Subflows and Conversations ....................................................................................................................... 136 6.6 Filters ................................................................................................................................................................. 137 6.6.1 Applying Filters ........................................................................................................................................... 137 6.6.2 Filter Types .................................................................................................................................................. 139 6.6.3 Variables and Scopes ................................................................................................................................... 139 6.6.4 Filter Dependencies ..................................................................................................................................... 139 6.7 Ajax ................................................................................................................................................................... 140 6.7.1 Ajax using Prototype ................................................................................................................................... 140 22.214.171.124 Remoting Linking .................................................................................................................................. 141 126.96.36.199 Updating Content ................................................................................................................................... 141 18.104.22.168 Remote Form Submission ...................................................................................................................... 141 184.108.40.206 Ajax Events ............................................................................................................................................ 142 6.7.2 Ajax with Dojo ............................................................................................................................................ 142 6.7.3 Ajax with GWT ........................................................................................................................................... 143 6.7.4 Ajax on the Server ....................................................................................................................................... 143 6.8 Content Negotiation ........................................................................................................................................... 144 7. Validation ............................................................................................................................................................... 148 7.1 Declaring Constraints ........................................................................................................................................ 148 7.2 Validating Constraints ....................................................................................................................................... 148 7.3 Validation on the Client ..................................................................................................................................... 149 7.4 Validation and Internationalization ................................................................................................................... 150 7.5 Validation Non Domain and Command Object Classes ................................................................................... 151 8. The Service Layer .................................................................................................................................................. 152 8.1 Declarative Transactions ................................................................................................................................... 152 8.2 Scoped Services ................................................................................................................................................. 153 8.3 Dependency Injection and Services ................................................................................................................... 153 8.4 Using Services from Java .................................................................................................................................. 154 9. Testing .................................................................................................................................................................... 156 9.1 Unit Testing ....................................................................................................................................................... 158 9.2 Integration Testing ............................................................................................................................................. 162 9.3 Functional Testing ............................................................................................................................................. 167 10. Internationalization ............................................................................................................................................... 169 10.1 Understanding Message Bundles .................................................................................................................... 169 10.2 Changing Locales ............................................................................................................................................ 169 10.3 Reading Messages ........................................................................................................................................... 169 10.4 Scaffolding and i18n ........................................................................................................................................ 170 11. Security ................................................................................................................................................................. 171 11.1 Securing Against Attacks ................................................................................................................................ 171 11.2 Encoding and Decoding Objects ..................................................................................................................... 172 11.3 Authentication ................................................................................................................................................. 174 11.4 Security Plug-ins ............................................................................................................................................. 175
........................................... 185 12.................................................4..........................................................1 REST .................................... 195 14........................................................................ 183 12...............................................6 Property Override Configuration ...............................................3 Understanding a Plug-ins Structure .................. 181 12...... 203 15.................................................................................................. Deployment ............. 189 13..............................1 Creating and Installing Plug-ins ............................................................................................................................... 177 12..... 204 16...................................................................................................... 187 13.............................................................................................................................................................................................................................................................................................................. 203 15................................................................................................................... 193 14.................................. 208 5 ...................................... Grails and Hibernate ............................... 191 13................................................................................................................... 189 13................................................................ 175 12... 202 15.................................................... 178 12.............................................................1 Mapping with Hibernate Annotations ............................................................................................................................... 193 14............................................................................2 Plugin Repositories ..............1 The Underpinnings of Grails ..................................................................................11............1 Spring Security ................................... 205 17.......................................................................................................................... 182 12................................................10 Understanding Plug-in Load Order ............................................................9 Participating in Auto Reload Events ...... 180 12.....................................................................................................................................3 Runtime Spring with the Beans DSL ................................................................................................................................................................................................................................ Web Services ........................................................................................................................................ 175 11....................................................2 Shiro .................. Plug-ins ......................................................................................2 Further Reading .............................8 Adding Dynamic Methods at Runtime ..............................2 SOAP ...................................................................................................6 Hooking into Build Events .......................................4 Providing Basic Artefacts .....................5 Property Placeholder Configuration ............ 183 12.....................................7 Hooking into Runtime Configuration .................................................................................... 201 14........................................ 197 14.................................................................................................................. 193 14........ Grails and Spring .............................................................................................................. 191 14..................................................................................5 Evaluating Conventions ................................ Scaffolding ................................2 Configuring Additional Beans ........................................4 The BeanBuilder DSL Explained ........................3 RSS and Atom ........................................................................................................................ 184 12............................................. 177 12.............................4..................
Dynamic frameworks like Rails. Grails is a full stack framework and attempts to solve as many pieces of the web development puzzle through the core technology and it's associated plug-ins. Grails builds on these concepts and dramatically reduces the complexity of building web applications on the Java platform. 6 . Included out the box are things like: An easy to use Object Relational Mapping (ORM) layer built on Hibernate An expressive view technology called Groovy Server Pages (GSP) A controller layer built on Spring MVC A command line scripting environment built on the Groovy-powered Gant An embedded Tomcat container which is configured for on the fly reloading Dependency injection with the inbuilt Spring container Support for internationalization (i18n) built on Spring's core MessageSource concept A transactional service layer built on Spring's transaction abstraction All of these are made easy to use through the power of the Groovy language and the extensive use of Domain Specific Languages (DSLs) This documentation will take you through getting started with Grails and building web applications with the Grails framework. however. Most modern web frameworks in the Java space are over complicated and don't embrace the Don't Repeat Yourself (DRY) principles. Django and TurboGears helped pave the way to a more modern way of thinking about web applications. is that it does so by building on already established Java technology like Spring & Hibernate. What makes it different.1. Introduction Java web development as it stands today is dramatically more complicated than it needs to be.
2 and below's plugin resolution mechanism has been replaced by one built on Ivy the upside of which is that you can now resolve Grails plugins against Maven repositories as well as regular Grails repositories.1. For example: <g:resource dir="${pluginContextPath}/images" file="foo. If you still need support for resolving plugins against secured SVN repositories then the IvySvn project provides a set of Ivy resolvers for resolving against SVN repositories.jpg" /> Additionally the above example will no longer link to an application image from a plugin view. Use 'grails help' for more info 2.http://grails.2 Upgrading from previous versions of Grails Although the Grails development team have tried to keep breakages to a minimum there are a number of items to consider when upgrading a Grails 1.3.1.x Plugin Repositories As of Grails 1.1 Downloading and Installing The first step to getting up and running with Grails is to install the distribution.0. including support for Webdav.x.x. HTTP.x Plugin paths In Grails 1.2.0 . Grails 1.x applications to Grails 1.jpg" /> In Grails 1.org/ Licensed under Apache Standard License 2. SSH and FTP.2 views have been made plugin aware and this is no longer necessary: <g:resource dir="images" file="foo.0 Grails home is set to: /Developer/grails-1. or 1.3. The major changes are described in detail below. Upgrading from Grails 1.1.2. To do so you need to change the above to: 7 . Ivy supports a much richer setter of repository resolvers for resolving plugins with. See the section on resolvers in the Ivy docs for all the available options and the section of plugin repositories in the user guide which explains how to configure additional resolvers. 1. Upgrading from Grails 1. To do so follow these steps: Download a binary distribution of Grails and extract the resulting zip file to a location of your choice Set the GRAILS_HOME environment variable to the location where you extracted the zip On Unix/Linux based systems this is typically a matter of adding something like the following export GRAILS_HOME=/path/to/grails to your profile On Windows this is typically a matter of setting an environment variable under My Computer/Advanced/Environment Variables Now you need to add the bin directory to your PATH variable: On Unix/Linux base system this can be done by doing a export PATH="$PATH:$GRAILS_HOME/bin" On windows this is done by modifying the Path environment variable under My Computer/Advanced/Environment Variables If Grails is working correctly you should now be able to type grails in the terminal window and see output similar to the below: Welcome to Grails 1. Getting Started 2.0 No script name specified.x typically a pluginContextPath variable was used to establish paths to plugin resources. Grails no longer natively supports resolving plugins against secured SVN repositories.2.
Example: static constraints = { author validator: { a -> assert a != Book. The StreamCharBuffer class implements all the same methods as String.author } } The above code can lead to a StackOverflowError in Grails 1.String instances but instead return a StreamCharBuffer instance.legacy.withNewSession { assert a != Book.CharSequence interface.findByTitle("My Book").<g:resource contextPath="" dir="images" file="foo.lang.builder=true Validation on Flush Grails now executes validation routines when the underlying Hibernate session is flushed to ensure that no invalid objects are persisted.author } } } Upgrading from Grails 1. if your application depends on the older semantics you can still use the now deprecated implementation by settings the following property to true in Config.jpg" /> The same rules apply to the javascript and render Tag and Body return values Tags no longer return java.groovy: grails. however code like this may break: def foo = body() if(foo instanceof String) { // do something } In these cases you should use the java. which both String and StreamCharBuffer implement: def foo = body() if(foo instanceof CharSequence) { // do something } New JSONBuilder There is a new version of JSONBuilder which is semantically different to earlier versions of Grails. If one of your constraints (such as a custom validator) is executing a query then this can cause an addition flush resulting in a StackOverflowError.2.json.findByTitle("My Book"). The solution is to run the query in a new Hibernate session (which is recommended in general as doing Hibernate work during flushing can cause other issues): static constraints = { author validator: { a -> Book. However.x 8 .lang.0.
reports.dir=".config.project.GRAILS_HOME" includeTargets << new File ( "${grailsHome}/scripts/Bootstrap.war.war.xml") 9 .jsessionid=true 5) The syntax used to configure Log4j has changed.project. since Java 5.1 now no longer supports JDK 1.dependencies grails.war.war.groovy to grails-app/conf/BuildConfig.webXml grails.copyToWebApp grails. Grails no longer stores plugins inside your PROJECT_HOME/plugins directory by default. See the user guide section on Logging for more information.property(environment:"env") grailsHome = Ant.1 and above ship with Groovy 1. If your application requires jsessionid you can re-enable its usage by adding the following to grails-app/conf/Config.4.0 Grails 1.destDir has been renamed to grails.groovy" ) Instead you should use the new grailsScript method to import a named script: includeTargets << grailsScript( "Bootstrap. If you have a library that is written in Groovy 1.Groovy 1. Plugin Changes Since 1.destFile) grails.0.properties.x stream until you are able to upgrade your JDK. Configuration Changes 1) The setting grails. 2) The following settings have been moved from grails-app/conf/Config. Java 5.war.6 before using it with Grails 1./plugins" Script Changes 1) If you were previously using Grails 1.groovy" ) 2) Due to an upgrade to Gant all references to the variable Ant should be changed to ant. This may result in compilation errors in your application unless you either re-install all your plugins or set the following property in grails-app/conf/BuildConfig.getResourceAsStream("grails-app/conf/my-config.plugins. 4) The use of jsessionid (now considered harmful) is disabled by default.0. 3) The root directory of the project is no long on the classpath."env.3 or below the following syntax is no longer support for importing scripts from GRAILS_HOME: Ant.antProject.6 and no longer supports code compiled against Groovy 1.reports.project. the result is that loading a resource like this will no longer work: def stream = getClass().views.classLoader.5 you will need to recompile it against Groovy 1.dependencies option is no longer supported.6 Grails 1.test. if you wish to continue using Grails then it is recommended you stick to the Grails 1.groovy: grails.base.resources 3) The grails.testing.enable.file (renamed from grails.1.java5.1.groovy: grails.dir for consistency.war.0 is now the baseline (see above).groovy: grails.5.
You should now navigate to this directory in terminal: 10 .withInputStream { stream -> // read the file } Command Line Changes The run-app-https and run-war-https commands no longer exist and have been replaced by an argument to run-app: grails run-app -https Data Mapping Changes 1) Enum types are now mapped using their String value rather than the ordinal value. REST Support Incoming XML requests are now no longer automatically parsed.xml").Instead you should use the Java File APIs with the basedir property: new File("${basedir}/grails-app/conf/my-config. You shouldn't need to change anything. you can use the new resource argument. You can revert to the old behavior by changing your mapping as follows: static mapping = { someEnum enumType:"ordinal" } 2) Bidirectional one-to-one associations are now mapped with a single column on the owning side and a foreign key reference. which enables parsing by default: "/book"(resource:"book") 2. To enable parsing of REST requests you can do so using the parseRequest argument inside a URL mapping: "/book"(controller:"book". however you may want to drop the column on the inverse side as it contains duplicate data.3 Creating an Application To create a Grails application you first need to familiarize yourself with the usage of the grails command which is used in the following manner: grails [command name] In this case the command you need to execute is create-app: grails create-app helloworld This will create a new directory inside the current one that contains the project.parseRequest:true) Alternatively.
gsp file.cd helloworld 2. Controllers are capable of dealing with web requests and to fulfil the "hello world!" use case our implementation needs to look like the following: class HelloController { def world = { render "Hello World!" } } Job done. You will note it has a detected the presence of your controller and clicking on the link to our controller we can see the text "Hello World!" printed to the browser window. 2.5 Getting Set-up in an IDE 11 .groovy.4 A Hello World Example To implement the typical "hello world!" example run the create-controller command: grails create-controller hello This will create a new controller (Refer to the section on Controllers for more information) in the grails-app/controllers directory called HelloController. Now start-up the container with another new command called run-app: grails run-app This will start-up a server on port 8080 and you should now be able to access your application with the URL: http://localhost:8080/helloworld The result will look something like the following screenshot: This is the Grails intro page which is rendered by the web-app/index.
2 to with TextMate run the following command to generate appropriate project files: grails integrate-with --textmate Alternatively TextMate can easily open any project with its command line integration by issuing the following command from the root of your project: mate . code completion and integration with Sun's Glassfish server.2 to with IntelliJ run the following command to generate appropriate project files: grails integrate-with --intellij NetBeans A good Open Source alternative is Sun's NetBeans.The application domain. For an overview of features see the NetBeans Integration guide on the Grails website which was written by the NetBeans team. See the STS Integration page for an overview.IntelliJ IDEA IntelliJ IDEA and the JetGroovy plug-in offer good support for Groovy & Grails developer.The service layer.The C in MVC. To integrate Grails 1.Unit and integration tests. services . Eclipse We recommend that users of Eclipse looking to develop Grails application take a look at SpringSource Tool Suite. views . 2. This typically means that the name and location of files is used instead of explicit configuration.Other Java sources test .Supporting sources groovy . domain . src .Gant scripts.6 Convention over Configuration Grails uses "convention over configuration" to configure itself. hence you need to familiarize yourself with the directory structure provided by Grails. Here is a breakdown and links to the relevant sections: grails-app . which provides a Groovy/Grails plugin that automatically recognizes Grails projects and provides the ability to run Grails applications in the IDE. 2. a GSP editor and quick access to Grails commands. TextMate Since Grails' focus is on simplicity it is often possible to utilize more simple editors and TextMate on the Mac has an excellent Groovy/Grails bundle available from the Texmate bundles SVN. i18n .7 Running an Application Grails applications can be run with the built in Tomcat server using the run-app command which will load a server on port 8080 by default: 12 .Tag libraries.Support for internationalization (i18n). scripts . To integrate Grails 1.top level directory for Groovy sources conf . controllers . which offers built in support for Grails including automatic classpath management.Web controllers . taglib .Other Groovy sources java . Refer to the section on Groovy and Grails support on the JetBrains website for a feature overview.Configuration sources.Groovy Server Pages.
It is of course up to you to populate these tests with valid test logic. However.port=8090 run-app More information on the run-app command can be found in the reference guide. A good set of VM flags would be: -server -Xmx512M 2.9 Deploying an Application Grails applications are deployed as Web Application Archives (WAR files).10 Supported Java EE Containers Grails runs on any Servlet 2. 2. NEVER deploy Grails using the run-app command as this command sets Grails up for auto-reloading at runtime which has a severe performance and scalability implication When deploying Grails you should always run your containers JVM with the -server option and with sufficient memory allocation.8 Testing an Application The create-* commands in Grails automatically create integration tests for you within the test/integration directory.4 and above container and is known to work on the following specific container products: 13 . information on which can be found in the section on Testing. and Grails includes the war command for performing this task: grails war This will produce a WAR file in the root of your project which can then be deployed as per your containers instructions.grails run-app You can specify a different port by using the server.port argument: grails -Dserver. if you wish to execute tests you can run the test-app command as follows: grails test-app Grails also automatically generates an Ant build.xml which can also run the tests by delegating to Grails' test-app command: ant test This is useful when you need to build Grails applications as part of a continuous integration platform such as CruiseControl. 2.
1 Resin 3.2 Jetty 6.0 SpringSource tc Server SpringSource dm Server 1. which in most cases can be worked around. To do this use one of the generate-* commands such as generate-all. A list of known deployment issues can be found on the Grails wiki.0) GlassFish v2 (Sun AS 9. create-domain-class and so on that will create Controllers and different artefact types for you.0 GlassFish v1 (Sun AS 9.Tomcat 5. 2.2 Websphere 6.1 Jetty 5 Weblogic 7/8/9/10 Some containers have bugs however.1) GlassFish v3 Prelude Sun App Server 8. 14 . These are merely for your convenience and you can just as easily use an IDE or your favourite text editor. For example to create the basis of an application you typically need a domain model: grails create-domain-class book This will result in the creation of a domain class at grails-app/domain/Book.12 Creating Artefacts Grails ships with a few convenience targets such as create-controller.groovy such as: class Book { } There are many such create-* commands that can be explored in the command line reference guide.11 Generating an Application To get started quickly with Grails it is often useful to use a feature called Scaffolding to generate the skeleton of an application. which will generate a controller and the relevant views: grails generate-all Book 2.5 Tomcat 6.1 Websphere 5.2 Oracle AS JBoss 4.
foo.bar.foo. Allows you to customise what libaries are included in the WAR file.grails.extensions .types .3.* … def config = ConfigurationHolder.Set this to false if you do not require native2ascii conversion of Grails i18n properties files grails. set this to 'html'.codec .yourportal. grails. This file uses Groovy's ConfigSlurper which is very similar to Java properties files except it is pure Groovy hence you can re-use variables and use proper Java types! You can add your own configuration in here.serverURL="http://my.groovy. War generation grails. The most common is via the GrailsApplication object.dependencies .encoding .serverURL . but since what configuration there is typically a one off.bar.locations .hello = "world" Then later in your application you can access these settings in one of two ways.views.A string specifying the server URL portion of absolute links. grails.mime.5 and above.A closure containing Ant builder syntax that is legal inside an Ant copy. typically you want to set-up a real database at some point and the way you do that is described in the following section.war.1.mime.war.commons. Configuration It may seem odd that in a framework that embraces "convention-over-configuration" that we tackle this topic now.1 Basic Configuration For general configuration Grails provides a file called grails-app/conf/Config.views.copyToWebApp .A list of the JARs that should be included in the WAR file for JDK 1.1 Built in options Grails also provides the following configuration options: grails.gsp.dependencies .The file encoding used for GSP source files (default is 'utf-8') grails.Sets the location where the war command should place the generated WAR file grails.groovy.com".file .bar. it is best to get it out the way. To reduce risk of XSS attacks. including server name e. for example: foo. Grails ships with an embedded container and in-memory HSQLDB meaning there isn't even a database to set-up. or 'base64' (default: 'none').hello The other way involves getting a reference to the ConfigurationHolder class that holds a reference to the configuration object: import org.Sets the default encoding regime for GSPs .config.war.The location of properties files or addition Grails Config files that should be merged with main configuration grails. 15 .default. 3.native2ascii .enable. grails.codehaus. However.Whether to use the file extension to dictate the mime type in Content Negotiation grails.hello 3.file.A closure containing Ant builder syntax or a list of JAR filenames.config.project.config assert "world" == config. grails. See createLink.java5. With Grails' default settings you can actually develop and application without doing any configuration whatsoever.war.can be one of 'none'.g.A map of supported mime types used for Content Negotiation grails. 'html'. which is available as a variable in controllers and tag libraries: assert "world" == grailsApplication.
1 Grails provides a Log4j DSL. see the section on deployment 3. Allows the application to do any other pre-warring stuff it needs to.groovy.groovy.grails.groovy located in the grails-app/conf directory.servlet'. Some useful loggers include: org. Grails processes the Config.grails.mortbay. You can also configure the root logger from the argument passed into the Log4J closure: 16 .commons .war.codehaus. You can configure the Root logger using the root method: root { error() additivity = true } The above example configures the root logger to log messages at the error level and above to the default standard out appender. Since 1.1.codehaus. org.grails.the default 'stdout' appender and a 'file' appender.grails.web . You can also configure the root logger to log to one or more named appenders: appenders { file name:'file'. test.See what Spring is doing org.grails.URL mapping debugging org.springframework .mapping .plugins .web.web.groovy.web.Core artefact information such as class loading etc.codehaus.for example "fileset()". Allows you to control what gets included in the WAR file from the "web-app" directory.hibernate .groovy.resources .log' // controllers GSP Essentially. 'org. each method translates into a log level and you can pass the names of the packages you want to log at that level as arguments to the method.Log plugin activity org.2 Logging Logging Basics Grails uses its common configuration mechanism to configure the underlying Log4j log system. For more information on using these options.Grails web request processing org.groovy.log' } root { debug 'stdout'.pages' // 'org. that you can use to configure Log4j an example of which can be seen below: log4j = { error warn } 'org.groovy and configures Log4j appropriately. and production environments.codehaus.groovy. 'file' additivity = true } Here the root logger will log to two appenders .groovy file allows you to specify separate logging configurations for development.See what Hibernate is doing The Root Logger The Root logger is the logger that all other loggers inherit from. grails.codehaus.grails. To configure logging you must modify the file Config. This single Config.A closure containing Ant builder syntax. file:'/var/logs/mylog.codehaus.
log4j.level = org. The following appenders are available by default: jdbc . The example above sets the name.Create an XML log file html .An appender that logs to a JDBC connection console .commons" Custom Layouts By default the Log4j DSL assumes that you want to use a PatternLayout.log" } } Each argument passed to the appender maps to a property of underlying Appender class.DEBUG … } The closure argument "root" is an instance of org.* log4j = { appenders { appender new RollingFileAppender(name:"myAppender". layout:pattern(conversionPattern: '%c{2} %m%n') } } 17 .groovy. so refer to the API documentation for Log4J to find out what properties and methods are available to you. file:"/tmp/logs/myApp. there are other layouts available including: xml . maxFileSize:1024.An appender that logs to rolling set of files For example to configure a rolling file appender you can do: log4j = { appenders { rollingFile name:"myAppender". Custom Appenders Using the Log4j you can define custom appenders.log4j = { root -> root.log4j.apache. maxFileSize:1024. If you prefer to simply create the appender programmatically yourself.An appender that logs to a file rollingFile .log4j.codehaus.apache.A Pattern layout You can specify custom patterns to an appender using the layout setting: log4j = { appenders { console name:'customAppender'. or you have your own appender implementation then you can simply call the appender method and appender instance: import org. maxFileSize and file properties of the RollingFileAppender class.An appender that logs to standard out file .apache.Creates an HTML log file simple . However.Level. file:"/tmp/logs/myApp } } You can then log to a particular appender by passing the name as a key to one of the log level methods from the previous section: error myAppender:"org.grails.Logger .A simple textual log pattern .
layout:pattern(conversionPattern: '%c{2} %m%n') } } Full stacktraces When exceptions occur.app.For service classes controller .1. This logs to a file called stacktrace.3 GORM Grails provides the following GORM configuration options: 18 .full.stacktrace VM property to true: grails -Dgrails.For bootstrap classes dataSource .app. Below is an example of its usage: def foo = "bar" log. This includes domain classes.controller.app" // Set for a specific controller debug "grails.<artefactType>.YourController" // Set for a specific domain class debug "grails.For data sources tagLib . Below is an example of how to configure logs for different Grails artefacts: log4j = { // Set level for all application artefacts info "grails. the full trace is always written to the StackTrace logger. tag libraries and so on. there can be an awful lot of noise in the stacktrace from Java and Groovy internals.but you can change this in your Config.app.groovy to do anything you like. some of the common ones are listed below: bootstrap . For example if you prefer full stack traces to go to standard out you can add this line: error stdout:"StackTrace" You can completely disable stacktrace filtering by setting the grails. When this happens.For tag libraries service .For domain entities 3.domain. controllers.debug "The value of foo is $foo" Logs are named using the convention grails. which logs to the console: log4j = { appenders { console name:'stdout'.log .tagLib" } The artefacts names are dictated by convention.For controllers domain .ClassName.This also works for the built-in appender "stdout". Grails filters these typically irrelevant details and restricts traces to non-core Grails/Groovy class packages.full.app.stacktrace=true run-app Logging by Convention All application artefacts have a dynamically added log property.Book" // Set for all taglibs info "grails.
someotherpackage'] grails.2 Environments Per Environment Configuration Grails supports the concept of per environment configuration.validation.gorm.If set to true.groovy. If the value is a list of Strings then the failOnError behavior will only be applied to domain classes in those packages (including sub-packages). This option may also be assigned a list of Strings representing package names.failOnError=true Enable failOnError for domain classes by package… grails. Enable failOnError for all domain classes… grails.ValidationException if validation fails during a save. replacing the need to do something like save(flush: true). causes the merge.grails.companyname.gorm.companyname.failOnError = ['com.shutdown=true" } } } Notice how the common configuration is provided at the top level and then an environments block specifies per environment settings for the dbCreate and url properties of the DataSource.groovy file within the grails-app/conf directory can take advantage of per environment configuration using the syntax provided by ConfigSlurper As an example consider the following default DataSource definition provided by Grails: dataSource { pooled = false driverClassName = "org.somepackage'.failOnError .gorm.hsqldb. Both the Config. causes the save() method on domain classes to throw a grails.'update' url = "jdbc:hsqldb:mem:devDB" } } test { dataSource { dbCreate = "update" url = "jdbc:hsqldb:mem:testDb" } } production { dataSource { dbCreate = "update" url = "jdbc:hsqldb:file:prodDb. The format is: grails [environment] [command name] 19 . Packaging and Running for Different Environments Grails' command line has built in capabilities to execute any command within the context of a specific environment. 'createeate-drop'. 'com. See the save method docs for more information.gorm.autoFlush = If set to true. 3.groovy file and the DataSource. This syntax can also be used within Config.jdbcDriver" username = "sa" password = "" } environments { development { dataSource { dbCreate = "create-drop" // one of 'create'. save and delete methods to flush the session.
"prod") } development { ctx. For example for 20 .3 The DataSource Since Grails is built on Java technology setting up a data source requires some knowledge of JDBC (the technology that doesn't stand for Java Database Connectivity). For example to create a WAR for the test environment you could do: grails test war If you have other environments that you need to target you can pass a grails.executeForCurrentEnvironment { production { // do something in production } development { // do something only in development } } 3.Environment class internally to execute. You can also use this class yourself to execute your own environment specific logic: Environment.setAttribute("env".util.util.DEVELOPMENT: configureForDevelopment() break case Environment. prod. there are 3 preset environments known to Grails: dev. To do so you can use the grails-app/conf/BootStrap. if you are using another database other than HSQLDB you need to have a JDBC driver. switch(Environment.current) { case Environment.setAttribute("env".groovy file's support for per-environment execution: def init = { ServletContext ctx -> environments { production { ctx. Essentially. production and test. and test for development.env variable to any command: grails -Dgrails. "bar") } Generic Per Environment Execution The previous BootStrap example uses the grails. "dev") } } ctx.Environment .. such as in a Gant script or a bootstrap class you can detect the environment using the Environment class: import grails.In addition.setAttribute("foo"..PRODUCTION: configureForProduction() break } Per Environment Bootstrapping Its often desirable to run code when your application starts up on a per-environment basis.env=UAT run-app Programmatic Environment Detection Within your code.
Drop the JAR into your project's lib directory.hibernate.The JDBC URL of the database dbCreate .Driver" dialect = org. For example the following is invalid: dataSource { boolean pooled = true // type declaration results in local variable … } Example of advanced configuration using extra properties: dataSource { pooled = true dbCreate = "update" url = "jdbc:mysql://localhost/yourDB" driverClassName = "com.jdbc.MySQL you would need Connector/J Drivers typically come in the form of a JAR archive.groovy. A typical configuration for MySQL may be something like: dataSource { pooled = true dbCreate = "update" url = "jdbc:mysql://localhost/yourDB" driverClassName = "com.hibernate.jdbc.mysql.A String or Class that represents the Hibernate dialect used to communicate with the database.The password used to establish a JDBC connection url .Extra properties to set on the DataSource bean. This file contains the dataSource definition which includes the following settings: driverClassName .The username used to establish a JDBC connection password .MySQL5InnoDBDialect username = "yourUser" password = "yourPassword" properties { maxActive = 50 maxIdle = 25 minIdle = 5 initialSize = 5 minEvictableIdleTimeMillis = 60000 timeBetweenEvictionRunsMillis = 60000 maxWait = 10000 validationQuery = "/* ping */" } } 3.Whether to auto-generate the database from the domain model or not pooled .dialect.Driver" dialect = org.dialect package for available dialects.mysql. Once you have the JAR in place you need to get familiar Grails' DataSource descriptor file located at grails-app/conf/DataSource. See the org.Enable SQL logging to stdout dialect .The class name of the JDBC driver username .3.1 DataSources and Environments 21 .MySQL5InnoDBDialect username = "yourUser" password = "yourPassword" } When configuring the DataSource do not include the type or the def keyword before any of the configuration settings as Groovy will treat these as local variable definitions and they will not be processed.dialect.Whether to use a pool of connections (defaults to true) logSql .hibernate. See the Commons DBCP BasicDataSource documentation. properties .
DataSource". but the way you define the DataSource remains the same. bar: "23" ].factory.sql. url: "jdbc:HypersonicSQL:database". maxIdle: "4" ]. however.naming. Using the Tomcat plugin you can define JNDI resources using the grails. and drops the schema at the end of a 22 . //required auth: "Container". Sometimes you are required to look-up a DataSource via JNDI.entries setting in grails-app/conf/Config. factory: "org.groovy: grails. maxActive: "8".3. Grails supports the definition of JNDI data sources as follows: dataSource { jndiName = "java:comp/env/myDataSource" } The format on the JNDI name may vary from container to container. so you can do: dataSource { // common settings here } environments { production { dataSource { url = "jdbc:mysql://liveip.Drops and re-creates the database when Grails starts.2 JNDI DataSources Referring to a JNDI DataSource Since many Java EE containers typically supply DataSource instances via the Java Naming and Directory Interface (JNDI). //optional driverClassName: "org. test.apache. "mail.mycompany. Grails' DataSource definition is "environment aware".com/liveDb" } } } 3. username: "dbusername".jdbcDriver".hsql.Session.host": "localhost" ] ] 3. // optional description: "Data source for Foo". "mail/session": [ type: "javax. password: "dbpassword". development etc.The previous example configuration assumes you want the same config for all environments: production.smtp. Configuring a Development time JNDI resource The way in which you configure JNDI data sources at development time is plugin dependent. "jdbc/EmployeeDB": [ type: "javax.3 Automatic Database Migration The dbCreate property of the DataSource definition is important as it dictates what Grails should do at runtime with regards to automatically generating the database tables from GORM classes. The options are: create-drop .3.BeanFactory". auth: "Container".MyBean".naming.mail.entries = [ "bean/MyBeanFactory": [ auth: "Container". type: "com.naming.
Although Grails does not currently support Rails-style Migrations out of the box.3.Drops and re-creates the database when Grails starts. update . The modifications are rather basic though.dataSourceUnproxied 3.groovy in grails-app/conf is fine in the majority of cases. there are currently three plugins that provide similar capabilities to Grails: Autobase (http://wiki. and you wouldn't be able to see changes that haven't been committed yet (assuming you have a sensible transaction isolation setting. any other value . but there may be circumstances where you want to maintain the configuration in a file outside the main application structure. Compares the configuration with the existing database schema and reports warnings. You can access this bean like any other Spring bean. create . but doesn't drop the schema at the end of a clean shutdown.g. validate . Both create-drop and create will destroy all existing data hence use with caution! In development mode dbCreate is by default set to "create-drop": dataSource { dbCreate = "create-drop" // one of 'create'.e. Don't specify any value if you want to manage databases yourself or by using a 3rd-party tool. its bean name is dataSourceUnproxied.'update' } What this does is automatically drop and re-create the database tables on each restart of the application. then retrieving a connection from the dataSource would be a new connection.does nothing.4 Externalized Configuration The default configuration file Config.Creates the database if it doesn't exist.clean shutdown. e.github. If this were not the case.4 Transaction-aware DataSource Proxy The actual dataSource bean is wrapped in a transaction-aware proxy so you will be given the connection that's being used by the current transaction or Hibernate Session if one is active. using dependency injection: class MyService { def dataSourceUnproxied … } or by pulling it from the ApplicationContext: def dataSourceUnproxied = ctx. Obviously this may not be what you want in production. The LiquiBase plugin and the DbMigrate plugin both of which are available via the grails list-plugins command 3. The "real" unproxied dataSource is still available to you if you need access to it.Makes no changes to your database. i. 'create-drop'. For example if you are deploying to a WAR some administrators prefer the configuration of the application to be 23 . Will not drop or modify anything. and modifies it if it does exist.com/RobertFischer/autobase). READ_COMMITTED or better). and generally only include adding missing columns and tables.
Detecting Versions at Runtime You can detect the application version using Grails' support for application metadata using the GrailsApplication class.6 Project Documentation Since Grails 1.externalized to avoid having to re-package the WAR due to a change of configuration.grails.grails/${appName}-config.1. The version is stored in the application meta data file called application. To change the version of your application you can run the set-version command: grails set-version 0. To do so you need to point Grails at the locations of the configuration files Grails should be using by adding a grails.config.properties".util.groovy"] In the above example we're loading configuration files (both Java properties files and ConfigSlurper configurations) from different places on the classpath and files located in USER_HOME.version'] If it is the version of Grails you need you can use: def grailsVersion = grailsApplication. "file:${userHome}/.metadata['app.grailsVersion 3. 24 . "file:${userHome}/.config.metadata['app.locations = [ "classpath:${appName}-config. In order to support deployment scenarios such as these the configuration can be externalized. the documentation engine that powers the creation of this documentation is available to your Grails projects. When you first create an application with the create-app command the version of the application is set to 0.2.grails/${appName}-config.* def grailsVersion = GrailsUtil.5 Versioning Versioning Basics Grails has built in support for application versioning.properties". "classpath:${appName}-config.version'] or the GrailsUtil class: import grails. For example within controllers there is an implicit grailsApplication variable that can be used: def version = grailsApplication.locations setting in Config.groovy: grails.properties in the root of the project. Ultimately all configuration files get merged into the config property of the GrailsApplication object and are hence obtainable from there.2 The version is used in various commands including the war command which will append the application version to the end of the created WAR file.groovy". Grails also supports the concept of property place holders and property override configurers as defined in Spring For more information on these see the section on Grails and Spring 3.
The following sections walk you through the syntax basics. Creating project documentation To use the engine you need to follow a few conventions. Firstly you need to create a src/docs/guide directory and then have numbered text files using the gdoc format.copyright . that belongs to a category called Controllers this can be done by creating a gdoc text file at the following location: + src/ref/Controllers/renderPDF. Each reference item belongs to a category and a category is a directory located in the src/docs/ref directory. formatting etc. For example: + src/docs/guide/1.doc.gdoc + src/docs/guide/2.The copyright message to display grails.The footer to use Other properties such as the name of the documentation and the version are pulled from your project itself. Getting Started.doc.license .The documentation engine uses a variation on the Textile syntax to automatically create project documentation with smart linking. Generating Documentation Once you have created some documentation (refer to the syntax guide in the next chapter) you can generate an HTML version of the documentation using the command: grails docs This command will output an docs/manual/index. For example say you defined a new method called renderPDF. The order is dictated by the numerical value at the beginning of the file name.html which can be opened to view your documentation.gdoc Configuring Output Properties There are various properties you can set within your grails-app/conf/Config. Introduction.authors . Creating reference items Reference items appear in the left menu on the documentation and are useful for quick reference documentation.footer .groovy file that customize the output of the documentation such as: grails.doc. Documentation Syntax As mentioned the syntax is largely similar to Textile or Confluence style wiki markup.The license of the software grails.gdoc The title of each chapter is taken from the file name. Basic Formatting Monospace: monospace @monospace@ Italic: italic _italic_ 25 .doc.The authors of the documentation grails.
A basic external link can either be defined using confluence or textile style markup: [SpringSource|http://www. Introduction" And then the link becomes: [Intro|guide:intro] This is useful since if you linked the to "1.springsource. Introduction] The documentation engine will warn you if any links to sections in your guide break.alias.intro="1.String] The documentation engine will automatically create the appropriate javadoc link in this case. To get around this you can create an alias inside grails-app/conf/Config.com/] or "SpringSource":http://www. Finally.png! Linking There are several ways to create links with the documentation generator. If you want to add additional APIs to the engine you can configure them in grails-app/conf/Config. Sometimes though it is preferable not to hard code the actual names of guide sections since you may move them around. For example: 26 .groovy: grails.com/ For links to other sections inside the user guide you can use the guide: prefix: [Intro|guide:1. to link to external APIs you can use the api: prefix.groovy. For example: [String|api:java. Introduction" chapter many times you would have to change all of those links.springsource.Bold: bold *bold* Image: !http://grails. To link to reference items you can use a special syntax: [controllers|renderPDF] In this case the category of the reference item is on the left hand side of the | and the name of the reference item on the right.lang.doc.org/images/new/grailslogo_topNav.
org/hibernate/stable/core/api" The above example configures classes within the org.hibernate package to link to the Hibernate website's API docs.grails.org.doc.api.<space>Heading3 h4.hibernate="http://docs.jboss.<space>Heading4 Unordered lists are defined with the use of the * character: * item 1 ** subitem 1 ** subitem 2 * item 2 Numbered lists can be defined with the # character: # item 1 Tables can be created using the table macro: Name Number Albert 46 Wilma 1348 James 12 {table} *Name* | *Number* Albert | 46 Wilma | 1348 James | 12 {table} Code and Notes You can define code blocks with the code macro: class Book { String title } 27 . Lists and Headings Headings can be created by specifying the letter 'h' followed by a number and then a dot: h3.
{code} class Book { String title } {code} The example above provides syntax highlighting for Java and Groovy code.resolution = { // config here } The default configuration looks like the following: 28 . Inside the grails-app/conf/BuildConfig.project.dependency.resolution property that configures how dependencies are resolved: grails.dependency.7 Dependency Resolution In order to control how JAR dependencies are resolved Grails features (since version 1.2) a dependency resolution DSL that allows you to control how dependencies for applications and plugins are resolved.project. but you can also highlight XML markup: <hello>world</hello> {code:xml} <hello>world</hello> {code} There are also a couple of macros for displaying notes and warnings: Note: This is a note! {note} This is a note! {note} Warning: This is a warning! {warning} This is a warning! {warning} 3.groovy file you can specify a grails.
name:'mysql-connector-java'.mysql:mysql-connector-java:5.repository.2 Dependency Repositories Remote Repositories Grails.org" //mavenRepo "http://repository.net/maven/2/" //mavenRepo "http://repository.java.codehaus.mysql:mysql-connector-java:5.5' } } The details of the above will be explained in the next few sections.jboss.1.com/maven2/ } dependencies { // specify dependencies here under either 'build'.1. either 'error'.codehaus.7.mysql'. name:'mysql-connector-java'.1. If you want to take advantage of a public repository you need to specify as such inside the repositories block: 29 .1.org" //mavenRepo "http://download.1 Configurations and Dependencies Grails features 5 dependency resolution configurations (or 'scopes') which you can take advantage of: build: Dependencies for the build system only compile: Dependencies for the compile step runtime: Dependencies needed at runtime but not for compilation (see above) test: Dependencies needed for testing but not at runtime (see above) provided: Dependencies needed at development time. // runtime 'com. name:'ehcache'. 'net.5' Multiple dependencies can be specified by passing multiple arguments: runtime 'com. For example if your application requires the MySQL driver to function at runtime you can specify as such: runtime 'com. [group:'net.ehcache'.5'].project. 3. You can also use a map-based syntax: runtime group:'com.dependency. version:'1. 'debug' or 'verbose' repositories { grailsHome() // uncomment the below to enable remote dependency resolution // from public Maven repositories //mavenCentral() //mavenRepo "http://snapshots. 'compile'.1' // Or runtime( [group:'com.g. // 'warn'.6. version:'5. when installed.1'] ) 3. does not use any remote public repositories. but not during WAR deployment Within the dependencies block you can specify a dependency that falls into one of these configurations by calling the equivalent method. There is a default grailsHome() repository that will locate the JAR files Grails needs from your Grails installation.mysql:mysql-connector-java:5.1. // 'runtime'.grails. e. version:'5.7. 'test' or 'provided' scopes.ehcache:ehcache:1.5' The above uses the string syntax which is group:name:version.resolution = { inherits "global" // inherit Grails' default dependencies log "warn" // log level of Ivy resolver. 'info'.sf.mysql'.5'.6.sf.
'builds'].authentication setting: 30 .repository/${it}/[organisation]/[module]/[revision]/[type } libResolver.name = "my-repository" libResolver.ivy.each { libResolver..groovy file using the grails." host = "localhost" username = "myuser" password = "mypass" } The above can also be placed in your USER_HOME/.repository/${it}/[organisation]/[module]/[revision]/[ libResolver.addArtifactPattern("http://my.project. To use the SpringSource Enterprise Bundle Repository you can use the ebr() method: repositories { ebr() } You can also specify a specific Maven repository to use by URL: repositories { mavenRepo "http://repository.ivy.codehaus.addIvyPattern("http://my. */ def libResolver = new org.plugins.resolver.grails/settings.apache.repositories { mavenCentral() } In this case the default public Maven repository is specified.org" } Local Resolvers If you do not wish to use a public Maven repository you can specify a flat file repository: repositories { flatDir name:'myRepo'.URLResolver() ['libraries'.settings = ivySettings resolver libResolver Authentication If your repository requires some form of authentication you can specify as such using a credentials block: credentials { realm = ". dirs:'/path/to/repo' } Custom Resolvers If all else fails since Grails builds on Apache Ivy you can specify an Ivy resolver: /* * Configure our resolver.
ivy.resolution = { inherits "global" // inherit Grails' default dependencies defaultDependenciesProvided true // all of the default dependencies will be "provided" by the c repositories { grailsHome() // … } dependencies { // … } } 3. 'warn'. 'debug' or 'verbose' log "warn" 3.5 Providing Default Dependencies Most Grails applications will have runtime dependencies on a lot of jar files that are provided by the Grails framework.dependency.7.4 Inherited Dependencies By default every Grails application inherits a bunch of framework dependencies.authentication = { credentials { realm = ". The dependency resolution DSL provides a mechanism to express that all of the default dependencies will be provided by the container. "ehcache" } 3. To obtain a report of an application's dependencies you can run the dependency-report command: 31 . the plugins installed and the application dependencies itself. either 'error'. An application may choose to have these jar files excluded from the war file. Hibernate etc." host = "localhost" username = "myuser" password = "mypass" } } 3.project..7. When a war file is created. These include libraries like Spring.grails.7. This is useful when the jar files will be provided by the container.project.7. 'info'. This is done through the line: inherits "global" Inside the BuildConfig. as would normally be the case if multiple Grails applications are deployed to the same container.3 Debugging Resolution If you are having trouble getting a dependency to resolve you can enable more verbose debugging from the underlying engine using the log method: // log level of Ivy resolver. If you wish exclude certain inherited dependencies then you can do so using the excludes method: inherits("global") { excludes "oscache". This is done by invoking the defaultDependenciesProvided method and passing true as an argument: grails. Sitemesh.groovy file.6 Dependency Reports As mentioned in the previous section a Grails application consists of dependencies inherited from the framework. all of these dependencies will be included in the war.
7.4. However.1. You can specify which configuration (scope) you want a report for by passing an argument containing the configuration name: grails dependency-report runtime 3. or an application dependency then you can override how a plugin resolves its dependencies inside an application using exclusions. 32 .xml and load dependencies from there. effectively excluding the javassist library as a dependency. Overriding Plugin JAR Dependencies in Your Application If a plugin is using a JAR which conflicts with another plugin.3.grails dependency-report This will output a report to the target/dependency-report directory by default.project.plugins:hibernate:1.0" ) { excludes "javassist" } } dependencies { runtime "javassist:javassist:3..8 Maven Integration When using the Grails Maven plugin. To do so simply add the following line to your BuildConfig. If you want to define a dependency that is resolved for use with the plugin but not exported to the application then you can set the exported property of the dependency: compile( 'org. test-app and so on then you can tell Grails' command line to load dependencies from the Maven pom.3.GA" } In this case the application explicitly declares a dependency on the "hibernate" plugin and specifies an exclusion using the excludes method.xml file instead. } The line pom true tells Grails to parse Maven's pom.GA') { exported = false } In this can the hibernate-core dependency will be available only to the plugin and not resolved as an application dependency.grails. When a plugin is installed into an application the application automatically inherits the dependencies of the plugin.hibernate:hibernate-core:3.7.groovy: grails. if you would like to continue using Grails regular commands like run-app.resolution = { pom true .xml file. 3.dependency. Grails' dependency resolution mechanics are disabled as it is assumed that you will manage dependencies via Maven's pom. For example: plugins { runtime( "org.7 Plugin JAR Dependencies Specifying Plugin JAR dependencies The way in which you specify dependencies for a plugin is identical to how you specify dependencies in an application.
grails/settings. url:"http://myserver/path/to/repo") } The syntax for configuring remote repositories matches the syntax from the remoteRepository element in the Ant Maven tasks..Installs a Grails project or plugin into your local Maven cache maven-deploy .xml file will be used. You need to configure the details of the repository specified by this 'id' within your grails-app/conf/BuildConfig. There are two key additional targets added by the plugin: maven-install .dependency.3.xml is already present in the root of the project. maven-install The maven-install command will install the Grails project or plugin artifact into your local Maven cache: grails maven-install In the case of plugins.distribution = { localRepository = "/path/to/my/local" remoteRepository(id:"myRepo"..home}/.Deploys a Grails project or plugin to a remote Maven repository By default this plugin will automatically generate a valid pom." privateKey="${user.project.9 Deploying to a Maven Repository If you are using Maven to build your Grails project. in which case this pom. If not.xml for you unless a pom. maven-deploy The maven-deploy command will deploy a Grails project or plugin into a remote Maven repository: grails maven-deploy It is assumed that you have specified the necessary <distributionManagement> configuration within a pom. you can use the standard Maven targets mvn install and mvn deploy.7. The plugin provides the ability to publish Grails projects and plugins to local and remote Maven repositories.groovy file: grails. you can deploy a Grails project or plugin to a Maven repository using the maven-publisher plugin. For example the following XML: <remoteRepository id="myRepo" url="scp://localhost/www/repository"> <authentication username=".groovy file or in your USER_HOMER/. whilst for application the application WAR file will be installed. the plugin zip file will be installed.xml or that you specify the id of the remote repository to deploy to: grails maven-deploy --repository=myRepo The repository argument specifies the 'id' for the repository.ssh/id_dsa"/> </remoteRepository> Can be expressed as: 33 .
2 The Maven groupId will be the same as the project name..).project.ssh/id_dsa" } By default the plugin will try to detect the protocol to use from the URL of the repository (ie "http" from "http://. privateKey:"${userHome}/.plugins". however if you need to explicitly specify a different protocol you can do: grails maven-deploy --repository=myRepo --protocol=webdav The available protocols are: http scp scpexe ftp webdav Groups.groovy: grails. 'artifactId' and a 'version'. unless you specify a different one in Config. 3.1' } 34 .". If your plugin does not specify a groupId then this defaults to "org.1' The 'artifactId' is taken from the plugin name.7.xml file.2.grails.groovy descriptor: String groupId = 'myOrg' String version = '0.10 Plugin Dependencies As of Grails 1. For example if you have a plugin called FeedsGrailsPlugin the artifactId will be "feeds". This plugin pulls this information from the Grails project conventions or plugin descriptor.. url:"scp://localhost/www/repository") { authentication username:".. Projects For applications this plugin will use the Grails application name and version provided by Grails when generating the pom.3 you can declaratively specify dependencies on plugins rather than using the install-plugin command: plugins { runtime ':hibernate:1." etc. To change the version you can run the set-version command: grails set-version 0. Artifacts and Versions Maven defines the notion of a 'groupId'.remoteRepository(id:"myRepo".mycompany" Plugins With a Grails plugin the groupId and version are taken from the following properties in the *GrailsPlugin.groupId="com.
You can specify to use the latest version of a particular plugin by using "latest.release" label only works with Maven compatible repositories.8' ) { transitive = false } runtime ':searchable:0.integration".integration' } Integration vs. You can combine this technique to specify an alternative version of a plugin: plugins { runtime( ':weceem:0.5.plugins is used.4' // specifies a fixed searchable version } 35 . If you have a regular SVN-based Grails repository then you should use "latest. And of course if you are using a Maven repository with an alternative group id you can specify a group id: plugins { runtime 'mycompany:hibernate:latest.integration' } Plugin Exclusions You can control how plugins transitively resolves both plugin and JAR dependencies using exclusions. Release The "latest.4' // specifies a fixed searchable version } You can also completely disable transitive plugin installs. in which case no transitive dependencies will be resolved: plugins { runtime( ':weceem:0.release' } The "latest. For example: plugins { runtime( ':weceem:0. If you don't want to include snapshot versions then you can use the "latest.grails.5.If you don't specify a group id the default plugin group id of org. By using the excludes method you can tell Grails not to transitively install the searchable plugin.integration" as the version number: plugins { runtime ':hibernate:latest.integration" version label will also include resolving snapshot versions.8' ) { excludes "searchable" } } Here we have defined a dependency on the "weceem" plugin which transitively depends on the "searchable" plugin.8' ) { excludes "searchable" // excludes most recent version } runtime ':searchable:0.release" label: plugins { runtime ':hibernate:latest.
it invokes the "default" target defined in that script.. Refer to the Command Line reference in left menu of the reference guide for more information about individual commands 4. When Grails executes a Gant script.groovy PROJECT_HOME/scripts/RunApp. So typing grails run-app Results in a search for the following files: USER_HOME/.groovy If multiple matches are found Grails will give you a choice of which one to execute.groovy GLOBAL_PLUGINS_HOME/*/scripts/RunApp. For example the following command: grails create-script compile-sources 36 . When you type: grails [command name] Grails does a search in the following directories for Gant scripts to execute: USER_HOME/. If there is no default. The Command Line Grails' command line system is built on Gant .groovy GRAILS_HOME/scripts/RunApp.1 Creating Gant Scripts You can create your own Gant scripts by running the create-script command from the root of your project. However..a simple Groovy wrapper around Apache Ant.grails/scripts/RunApp. Grails will quit with an error.4. Grails takes it a bit further through the use of convention and the grails command.grails/scripts PROJECT_HOME/scripts PROJECT_HOME/plugins/*/scripts GRAILS_HOME/scripts Grails will also convert command names that are in lower case form such as run-app into camel case. To get a list and some help about the available commands type: grails help Which outputs usage instructions and the list of commands Grails is aware of: Usage (optionals marked with *): grails [environment]* [target] [arguments]* Examples: grails dev run-app grails create-app books Available Targets (type grails help 'target-name' for more info): grails bootstrap grails bug-report grails clean grails compile .groovy PLUGINS_HOME/*/scripts/RunApp.
Of particular use are the compile.mkdir(dir:"mkdir") ant. You can also "depend" on other targets using the depends method demonstrated in the default target above. In previous versions of Grails (1. you should move it into a shared script that doesn't have a default target at all. you can use whichever you prefer . package and bootstrap scripts.Will create a script called scripts/CompileSources. An alternative approach is to use the setDefaultTarget() method: target("clean-compile": "Performs a clean compilation on the app's source files. the variable was Ant. We'll talk some more about this in the next section.delete(dir:"output") } target(compile:"Compile some sources") { ant. compile) } target(clean:"Clean out things") { ant.there don't seem to be any major advantages in either case.mkdir(dir:"mkdir") ant.3 and below). compile) } target(clean:"Clean out things") { ant. with a capital first letter.2 Re-using Grails scripts Grails ships with a lot of command line functionality out of the box that you may find useful in your own scripts (See the command line reference in the reference guide for info on all the commands). although we have put the call to setDefaultTarget() at the end of the script in this example.0. we specified a target with the explicit name "default". The default target In the example above. Also. Which approach is better? To be honest.e. there is an implicit ant variable that allows access to the Apache Ant API. it can go anywhere as long as it comes after the target it refers to ("clean-compile" in this case). destdir:"output") } setDefaultTarget("clean-compile") This allows you to call the default target directly from other scripts if you wish. i. This is one way of defining the default target for a script.delete(dir:"output") } target(compile:"Compile some sources") { ant.javac(srcdir:"src/java". One thing we would say is that if you want to allow other scripts to call your "default" target.javac(srcdir:"src/java".groovy. 4. A Gant script itself is similar to a regular Groovy script except that it supports the concept of "targets" and dependencies between them: target(default:"The default target is the one that gets executed by Grails") { depends(clean. The bootstrap script for example allows you to bootstrap a Spring ApplicationContext instance to get access to the data source and so on (the integration tests use this): 37 . destdir:"output") } As demonstrated in the script above.") { depends(clean.
Anything that starts with an "_" is designed for re-use.. There are many more scripts provided by Grails.0. in pre-1. $GRAILS_HOME/scripts). In pre-1.getBean('dataSource'). you must use includeTargets << new File(. Core Grails targets As you saw in the example at the beginning of this section. you use neither the File." scripts were not available. Again.tools.groovy") includeTargets << gant.. Adds an event(String eventName. for example "Init. just Grails ones).1 versions of Grails. You can then depend upon or invoke those targets as if they had been defined in the current script.e. it's quite specialised. included by almost all other Grails scripts. Contains all the shared test code. The mechanism for doing this is the includeTargets property. Provides a parseArguments target that does what it says on the tin: parses the arguments provided by the user when they run your script. Here is a list of Grails scripts that you may want to re-use: Script _GrailsSettings _GrailsEvents _GrailsClasspath _GrailsProxy _GrailsArgParsing _GrailsTest _GrailsRun Description You really should include this! Fortunately.includeTargets << grailsScript("_GrailsBootstrap") target ('default': "Load the Grails interactive shell") { depends( configureProxy. you need to include this.close() } } Pulling in targets from other scripts Gant allows you to pull in all targets (except "default") from another Gant script. Again. include this script. you typically include the corresponding command script.. List args) method.groovy".nor the class-based syntax for includeTargets when including core Grails targets. it is included automatically by all other Grails scripts bar one (_GrailsProxy). you should use the special grailsScript() method that is provided by the Grails command launcher (note that this is not available in normal Gant scripts.) and specify the script's location in full (i. test. look into the Gant documentation. configureApp ) Connection c try { // do something with connection c = appCtx.getConnection() } finally { c?.groovy" or "Bootstrap. so it is worth digging into the scripts themselves to find out what kind of targets are available. loadApp. include this script so that you don't run into problems with proxies.4 versions of Grails you cannot use the grailsScript() method. Provides all you need to run the application in the configured servlet container. Simply "append" a file or class to it using the left-shift operator: includeTargets << new File("/path/to/my/script. If you want to fire events.Ivy Don't worry too much about the syntax using a class. 38 . and runtime classpaths. If you're interested. If you want to access the internet. If you want to use or play with them. The syntax for the grailsScript() method is pretty straightforward: simply pass it the name of the Grails script you want to include. Useful if you want to add any extra tests. Instead. classpath. Also. Sets up compilation. without any path information. packageApp. Instead. Adds them to the argsMap property. the "_Grails. so you usually don't have to include it explicitly. Instead.. either normally (runApp/runAppHttps) or from a WAR file (runWar/runWarHttps). included by almost all other Grails scripts.
4.groovy. all the registered handlers for that event are executed. To pass arguments to a target. Defining event handlers Event handlers are defined in scripts called _Events.you can split it like this: .") { depends(./scripts/_FunctionalTests. so you just need to declare them in the relevant _Events.plugin-specific event handlers GLOBAL_PLUGINS_HOME/*/scripts . and provide simple command scripts that parse any command line arguments and delegate to the targets in the internal script. That is Grails' way of determining that a script is _internal_.3 Hooking into Events Grails provides the ability to hook into scripting events. so it is possible to hook into events triggered by plugin scripts. That is also why they don't have a default target. In versions of Grails prior to 1.. The following example can be put in your /scripts directory to demonstrate the feature: 39 .groovy file.event handlers provided by global plugins Whenever an event is fired.groovy. Put argument parsing into the "command" script.groovy: includeTargets << grailsScript("_GrailsTest") target(runFunctionalTests: "Run functional tests. Avoid name clashes by using closures assigned to script variables instead of targets.groovy: includeTargets << new File("${basedir}/scripts/_FunctionalTests. The list of possible events is not fixed in any way. These are events triggered during execution of Grails target and plugin scripts.0. Grails searches for these scripts in the following locations: USER_HOME/. or in other words that it has not corresponding "command".user-specific event handlers PROJECT_HOME/scripts .. You can then pass arguments direct to the closures.grails/scripts .groovy") target(default: "Runs the functional tests for this project. for which there is no equivalent event in the core target scripts.Script architecture You maybe wondering what those underscores are doing in the names of the Grails scripts. create some script variables and initialise them before calling the target.groovy. So you can't run "grails _grails-settings" for example. Event handlers are blocks defined in _Events./scripts/FunctionalTests. that is without the leading underscore. the script was called Events. The mechanism is deliberately simple and loosely specified. Internal scripts are all about code sharing and re-use. Put the bulk of the implementation in the internal script. 4. with a name beginning with "event". Say you have a script that runs some functional tests .) … } Here are a few general guidelines on writing scripts: Split scripts into a "command" script and an internal one.") { depends(runFunctionalTests) } . In fact. we recommend you take a similar approach in your own scripts: put all your targets into an internal script that can be easily shared.applicaton-specific event handlers PLUGINS_HOME/*/scripts . Note that the registration of handlers is performed automatically by Grails.
.javadoc or groovydoc Called when documentation generation has ended . passing the kind of compile source or tests Called when documentation generation is about to start . eventStatusFinal.source or tests Called when compilation is finished.source or tests CompileEnd . eventStatusUpdate. even if the target does not exit the scripting environment Called when a create-xxxx script has completed and created an artefact Called whenever a project source filed is created. i.). when completing a target..javadoc or groovydoc Called during classpath initialization so plugins can augment the classpath with rootLoader. Note that this augments the classpath after event scripts are loaded so you cannot use this to load a class that your event script needs to import. passing the kind of compile .artefactName CreatedFile Exiting fileName returnCode PluginInstalled pluginName CompileStart CompileEnd DocStart DocEnd kind kind kind kind SetClasspath rootLoader PackagingEnd none 40 . passing the kind of compile . name -> println "Created $type $name" } eventStatusUpdate = { msg -> println msg } eventStatusFinal = { msg -> println msg } You can see here the three handlers eventCreatedArtefact. Grails provides some standard events. For example the compile command fires the following events: CompileStart . Called at the end of packaging (which is called prior to the Tomcat server being started and after web.addURL(. which are documented in the command line reference guide.xml is generated) CreatedArtefact artefactType.source or tests Triggering events To trigger an event simply include the Init.Called when compilation starts.e. although you can do this if you load the class by name.groovy script and call the event() closure: includeTargets << grailsScript("_GrailsEvents") event("StatusFinal". not including files constantly managed by Grails Called when the scripting environment is about to exit cleanly Called after a plugin has been installed Called when compilation starts.Called when compilation is finished.eventCreatedArtefact = { type. ["Super duper plugin action complete!"]) Common Events Below is a table of some of the common events that can be leveraged: Event StatusUpdate StatusError StatusFinal Parameters message message message Description Passed a string indicating current script status/progress Passed a string indicating an error message from the current script Passed a string indicating the final script status message. passing the kind of compile .
you could either run this command: grails -Dgrails.work. The location of the Grails installation in use (may be null).dir globalPluginsDir grails.util. but they should be treated as read-only: Property baseDir userHome grailsHome grailsVersion grailsEnv Description The location of the project.verbose false The BuildSettings class has some other properties too. these properties aren't much good if you can't get hold of them.grails/<grailsVersion> <grailsWorkDir>/projects/<baseDirName> <projectWorkDir>/classes <projectWorkDir>/test-classes <projectWorkDir>/test/reports <projectWorkDir>/resources <projectWorkDir>/plugins <grailsWorkDir>/global-plugins projectPluginsDir grails.groovy file: 41 . Of course.project.work.reports. The version of Grails being used by the project.project.project.4 Customising the build Grails is most definitely an opinionated framework and it prefers convention to configuration.dir grails.project.work. It controls where classes are compiled to. compileDependencies A list of compile-time project dependencies as File instances.class. testDependencies A list of test-time project dependencies as File instances.project.plugins. what dependencies the application has. and other such settings.4. You can also access it from your code by using the grails. but this doesn't mean you can't configure it. runtimeDependencies A list of runtime-time project dependencies as File instances.simply use the "config option" name.class.dir grails.BuildSettingsHolder class.project.global.dir grails. In this section. Overriding the defaults All of the properties in the first table can be overridden by a system property or a configuration option .plugins.dir grails. The user's home directory.project.dir=work compile or add this option to your grails-app/conf/BuildConfig. but this isn't recommended.dir Default value $USER_HOME/.dir verboseCompile grails. to change the project working directory.project.compile. Fortunately that's easy to do: an instance of BuildSettings is available to your scripts via the grailsSettings script variable.test. we look at how you can influence and modify the standard Grails build. you first need to know what you can customise.resource. For example. Here is a selection of the configuration options and their default values: Property grailsWorkDir projectWorkDir classesDir testClassesDir testReportsDir resourcesDir Config option grails. The core of the Grails build configuration is the grails. which contains quite a bit of useful information. The defaults In order to customise a build. The current Grails environment.util.BuildSettings class.test.dir grails.
copyToWebApp grails. which in turn takes precedence over the default values. Path to a custom web.war. "target/my-app. tests are assumed to have a suffix of "Tests".config. whereas the latter contains those that affect the application at runtime.xml file for you containing the following targets: clean .testing.resources grails.Compiles your application's source code test . Ant Integration When you create a Grails application via the create-app command. What happens if you use both a system property and a configuration option? Then the system property wins because it takes precedence over the BuildConfig.webXml grails.port. such as ones for specifying the port that the embedded servlet container runs on or for determining what files get packaged in the WAR file.server. It overrides the default behaviour of including everything under "web-app".nameSuffix grails. resources. Grails automatically creates an Apache Ant build. It's not limited to the options in the first table either: you will find build configuration options dotted around the documentation.groovy file. You can use any Ant tasks to do anything you like.file grails.groovy file is a sibling of grails-app/conf/Config. A closure containing "fileset()" entries that allows you complete control over what goes in the root of the WAR. another common suffix is "Test".Runs the unit tests 42 . and plugins. Legacy approach to adding extra dependencies to the compiler classpath.http grails. Available build settings Name grails.war.5 Ant and Maven If all the other projects in your team or company are built using a standard build tool such as Ant or Maven. so setting the project working directory like this would also relocate the compiled classes. you become the black sheep of the family when you use the Grails command line to build your application. Fortunately.https grails. A closure containing "fileset()" entries that allows you complete control over what goes in the WAR's "WEB-INF/lib" directory.dir = "work" Note that the default values take account of the property values they depend on.xml template). Port to run the embedded servlet container on for HTTPS ("run-app --https" and "run-war --https"). you can easily integrate the Grails build system into the main build tools in use today (well.server.base.testing.patterns grails.project.war. For example. The location to generate Grails' web.work.web.war. Integer.groovy .xml 4. For example.war". which is set by the next property.xml file to use for the application (alternative to using the web.dependencies grails. The BuildConfig.dependencies Description Port to run the embedded servlet container on ("run-app" and "run-war"). A string containing the file path of the generated WAR file.Cleans the Grails application compile . By default.the former contains options that only affect the build. It is typically used to remove files from the staging directory before that directory is jar'd up into a WAR. Integer.xml to grails. the ones in use in Java projects at least).compiler.grails.project. A list of Ant path patterns that allow you to control which files are included in the tests. A closure that takes the location of the staging directory as its first argument. The patterns should not include the test case suffix. along with its full name (include extension). test classes. You can change it to anything you like but setting this option.port.project. Set it to a closure containing "fileset()" entries.
Maven Integration From 1. "-unit -xml". the version created by Octo. For an example of their use. runtimeClasspath .Empty by default. all of which are standard Ant path structures: classpath . Defaults to "". Advanced setting: adds the application's runtime classpath to the build classpath if true. "TestApp". testClasspath . Typically includes everything in runtimeClasspath. With the task defined. but effectively supersedes. If you are using the home attribute and put your own dependencies in the lib directory. No. Grails provides integration with Maven 2 via a Maven plugin.Creates a WAR file deploy . unless home is set or you use a classpath element. No. To use the task. so that needs to be on the classpath at least. The name of the Grails script to run. which means that it will automatically download all the requisite Grails JAR files and other dependencies on demand.run . You should also include the "groovy-all" JAR.classpath"/> This raises the question: what should be in "grails.g.Classpath used to compile the application's classes. then you don't even need to use any of them. Typically includes everything in @compileClasspath.g.Classpath used to run the application and package the WAR. Defaults to the script default. The current Maven plugin is based on. not just the ones used by the generated build file.GrailsTask" classpathref="grails. unless classpath is specified. you must first declare it: <taskdef name="grailsTask" classname="grails.classpath"? The task itself is in the "grails-bootstrap" JAR artifact.The build classpath (used to load Gant and the Grails scripts). No. You don't even have to install Grails locally to use it! That makes it particularly useful for continuous integration systems such as CruiseControl or Hudson It uses the Grails Ant task to hook into the existing Grails build system. but can be used to implement automatic deployment Each of these can be run by Ant. Required Yes. take a look at the generated Ant build file for new apps. Yes. Must include the "grails-bootstrap" artifact and should include "grails-scripts". How you populate these paths is up to you. Defaults to true. for example: ant war The build file is all geared up to use Apache Ivy for dependency management. classpathref script args environment includeRuntimeClasspath The task also supports the following nested elements. Yes. Classpath to load Grails from. who did a great job. all you need is Maven 2 installed and set up. you just need to use it! The following table shows you what attributes are available: Attribute home Description The location of the Grails installation directory to use for the build.1 onwards. The Grails environment to run the script in. This is because you no longer need to install Grails separately to use it with Maven! 43 . Preparation In order to use the new plugin. e. e.Equivalent to "grails run-app" war .Classpath used to compile and run the tests. compileClasspath . The arguments to pass to the script.ant. The task allows you to run any Grails script that's available.
3.5</target> </configuration> </plugin> to <plugin> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1. if you want to set target JDK to Java 6.0.ga: not found :: javassist#javassist.3.6</source> <target>1.The Maven 2 integration for Grails has been designed and tested for Maven 2. but everything else must be as written.grails \ -DarchetypeArtifactId=grails-maven-archetype \ -DarchetypeVersion=1.0. the next step is to create the project structure that you're used to.xml and change <plugin> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.GA: not found :::::::::::::::::::::::::::::::::::::::::::::: 44 .5</source> <target>1.9 and above.hibernate#hibernate-commons-annotations. But first.3.6</target> </configuration> </plugin> Then you're ready to create the project structure: cd my-app mvn initialize if you see a message similar to this: :::::::::::::::::::::::::::::::::::::::::::::: :: UNRESOLVED DEPENDENCIES :: :::::::::::::::::::::::::::::::::::::::::::::: :: org. What you won't see is anything that looks like a Grails application. The default mvn setup DOES NOT supply sufficient memory to run the Grails environment.8. So.0.3. group ID and artifact ID you want for your application. We recommend that you add the following environment variable setting to prevent poor performance: export MAVEN_OPTS="-Xmx512m -XX:MaxPermSize=192m" Creating a Grails Maven Project To create a Mavenized Grails project simply run the following command: mvn archetype:generate -DarchetypeGroupId=org.2 \ -DgroupId=example -DartifactId=my-app Choose whichever grails version. This will create a new Maven project with a POM and a couple of other files. do that now. It will not work with earlier versions. Open my-app/pom.
Calls the create-script command grails:create-service . The plugin integrates into the standard build cycle. That doesn't help though when you want to attach a plugin's command to a particular phase. Adding Grails commands to phases The standard POM created for you by Grails already attaches the appropriate core Grails commands to their corresponding build phases. so "compile" goes in the "compile" phase and "war" goes in the "package" phase. mvn install . How do you make sure that your functional tests (using which ever plugin you have decided on) are run during the "integration-test" phase? Fear not: all things are possible.Calls the generate-controller command grails:generate-views .Creates a new Maven POM for an existing Grails project grails:create-script .Calls the create-controller command grails:create-domain-class . mvn package . In this case. see above.Calls the create-tag-lib command grails:create-unit-test .Calls the install-templates command grails:list-plugins . The solution is to create a POM for the existing project using this Maven command (substitute the version number with the grails version of your existing project): mvn org. you can associate the command to a phase using an extra "execution" block: 45 .3.Calls the create-integration-test command grails:create-pom . you can immediately start using the standard phases. up to date list.Calls the create-domain-class command grails:create-integration-test . mvn compile .Calls the list-plugins command grails:package . run mvn grails:help Mavenizing an existing project Creating a new project is great way to start.Calls the package command grails:run-app .mycompany When this command has finished.Executes an arbitrary Grails command line script grails:generate-all . but what if you already have one? You don't want to create a new project and then copy the contents of the old one over.groovy:20 and uncomment the following line: mavenCentral() call again: mvn initialize Now you have a Grails application all ready to go.Calls the uninstall-plugin command For a complete. Note that you have to specify a group ID when creating the POM.grails:grails-maven-plugin:1.Calls the generate-all command grails:generate-controller . You may also want to set target JDK to Java 6. You can also take advantage of some of the Grails commands that have been wrapped as Maven goals: grails:create-controller .Calls the install-plugin command grails:install-templates .Calls the create-service command grails:create-taglib . mvn test . such as mvn package.edit grails-app/conf/BuildConfig.Calls the create-unit-test command grails:exec .Calls the generate-views command grails:install-plugin .Calls the run-app command grails:uninstall-plugin . so you can use the standard Maven phases to build and package your app: mvn clean .2:create-pom -DgroupId=com. The classic example is functional tests.
and optionally specify the arguments via the args property: mvn grails:exec -Dcommand=create-webtest -Dargs=Book Debugging a Grails Maven Project Maven can be launched in debug mode using the "mvnDebug" command.address=5005" mvn grails:run-app Raising issues If you come across any problems with the Maven integration. 46 .suspend=y. please raise a JIRA issue as a sub-task of GRAILS-3547. To launch your Grails application in debug. which can be used to run any Grails command.<plugin> <groupId>org.grails</groupId> <artifactId>grails-maven-plugin</artifactId> <version>1.3. Simply pass the name of the command as the command system property. simply run: mvnDebug grails:run-app The process will be suspended on startup and listening for a debugger on port 8000.server=y. and launch Maven via the default "mvn" command: MAVEN_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket. this can be specified using the MAVEN_OPTS environment variable. If you need more control of the debugger.2</version> <extensions>true</extensions> <executions> <execution> <goals> … </goals> </execution> <!-.Add the "functional-tests" command to the "integration-test" phase --> <execution> <id>functional-tests</id> <phase>integration-test</phase> <goals> <goal>exec</goal> </goals> <configuration> <command>functional-tests</command> </configuration> </execution> </executions> </plugin> This also demonstrates the grails:exec goal.
You can also write Grails domain classes in Java.1 Basic CRUD Try performing some basic CRUD (Create/Read/Update/Delete) operations. Under the hood it uses Hibernate 3 (an extremely popular and flexible open source ORM solution) but because of the dynamic nature of Groovy. the fact that it supports both static and dynamic typing.1 Quick Start Guide A domain class can be created with the create-domain-class command: grails create-domain-class Person This will create a class at the location grails-app/domain/Person.addToAuthors(name:"Guillaume LaForge") .5. Grails will automatically generated/modify the database tables for you. They hold state about business processes and hopefully also implement behavior. GORM is Grails' object relational mapping (ORM) implementation. "create" or "create-drop" on your DataSource.groovy such as the one below: class Person { } If you have the dbCreate property set to "update". Below is a preview of GORM in action: def book = Book.addToAuthors(name:"Dierk Koenig") . set its properties and call save: 47 . Object Relational Mapping (GORM) Domain classes are core to any business application. They are linked together through relationships. and the convention of Grails there is less configuration involved in creating Grails domain classes. either one-to-one or one-to-many. 5. You can customize the class by adding properties: class Person { String name Integer age Date lastVisit } Once you have a domain class try and manipulate it via the shell or console by typing: grails console This loads an interactive GUI where you can type Groovy commands.1. See the section on Hibernate Integration for how to write Grails domain classes in Java but still use dynamic persistent methods.save() 5.findByTitle("Groovy in Action") book . Create To create a domain class use the Groovy new operator.
or throws an exception if no record is found for the specified id. lastVisit:new Date()) p.load(1) This incurs no database access until a method other than getId() is called. authors.delete() 5.save() Delete To delete an instance use the delete method: def p = Person. a release date.save() The save method will persist your class to the database using the underlying Hibernate ORM layer. These are modeled in GORM as Groovy classes so a Book class may have a title. an ISBN number and so on. Update To update an instance. The next few sections show how to model the domain in GORM. Hibernate then initializes the proxied instance. customers and publishers to name a few. In addition.def p = new Person(name:"Fred". set some properties and then simply call save again: def p = Person. Read Grails transparently adds an implicit id property to your domain class which you can use for retrieval: def p = Person. You can also load an object in a read-only state by using the read method: def p = Person. To create a domain class you can run the create-domain-class target as follows: grails create-domain-class Book 48 .name = "Bob" p.read(1) In this case the underlying Hibernate engine will not do any dirty checking and the object will not be persisted. you can also load an proxy for an instance by using the load method: def p = Person.2 Domain Modelling in GORM When building Grails applications you have to consider the problem domain you are trying to solve. Note that if you explicitly call the save method then the object is placed back into a read-write state.id This uses the get method that expects a database identifier to read the Person object back from the db.get(1) p.get(1) p.get(1) assert 1 == p. For example if you were building an Amazon bookstore you would be thinking about books. age:40.
The result will be a class at grails-app/domain/Book. The SQL types are auto-detected from the Java types. but can be customized via Constraints or the ORM DSL. and is defined trivially using a property of the type of another domain class. For example releaseDate maps onto a column release_date. a relationship exists only in the direction it is defined. For example: class Book { String title Date releaseDate String ISBN } Each property is mapped to a column in the database.groovy class into a sub directory under the domain directory and add the appropriate package declaration as per Groovy (and Java's) packaging rules.1 Association in GORM Relationships define how domain classes interact with each other. 5.1 One-to-one A one-to-one relationship is the simplest kind. The above class will map automatically to a table in the database called book (the same name as the class). Consider this example: Example A class Face { Nose nose } class Nose { } In this case we have unidirectional many-to-one relationship from Face to Nose. 5.2. This behaviour is customizable through the ORM Domain Specific Language Now that you have a domain class you can define its properties as Java types. where the convention for column names is all lower case separated by underscores.1.2. To make it a true one-to-one you should make nose unique: class Face { Nose nose static constraints = { nose unique: true } } class Nose { } To make this relationship bidirectional define the other side as follows: 49 .groovy: class Book { } If you wish to use packages you can move the Book. Unless specified explicitly at both ends.
example Author.save() // will cause an error Another important implication of belongsTo is that if you delete a Face instance the Nose will be deleted too: def f = Face. With Grails you define such a relationship with the hasMany setting: class Author { static hasMany = [ books : Book ] String name } class Book { String title } In this case we have a unidirectional one-to-many. 5. example Book. Grails will. by default.Example B class Face { Nose nose } class Nose { static belongsTo = [face:Face] } In this case we use the belongsTo setting to say that Nose "belongs to" Face.2.delete() // both Face and Nose deleted In the previous example the foreign key associated the Face with the Nose is stored in the parent as column called nose_id. Note that the inverse is not true and will result in an error due to a transient Face: new Nose(face:new Face()).save() The example above will save both face and nose.1. map this kind of relationship with a join 50 . has many instances of a another class.2 One-to-many A one-to-many relationship is when one class.get(1) f. The result of this is that we can create a Face and save it and the database updates/inserts will be cascaded down to Nose: new Face(nose:new Nose()). If you want the foreign key to be stored in the child you need a hasOne association: Example C class Face { static hasOne = [nose:Nose] } class Nose { Face face } In this example you get a bidirectional one-to-one where the foreign key column is stored in the nose table inside a column called face_id.
each { println it.2. but not deletes unless a belongsTo is also specified: class Author { static hasMany = [ books : Book ] String name } class Book { static belongsTo = [author:Author] String title } If you have two properties of the same type on the many side of a one-to-many you have to use mappedBy to specify which the collection is mapped: class Airport { static hasMany = [flights:Flight] static mappedBy = [flights:"departureAirport"] } class Flight { Airport departureAirport Airport destinationAirport } This is also true if you have multiple collections that map to different properties on the many side: class Airport { static hasMany = [outboundFlights:Flight.util. This can be used to iterate over the collection: def a = Author.get(1) a.books. If you need "eager" fetching you can use the ORM DSL or specify eager fetching as part of a query The default cascading behaviour is to cascade saves and updates. This can lead to the n+1 problem if you are not careful. inboundFlights:Flight] static mappedBy = [outboundFlights:"departureAirport". inboundFlights:"destinationAirport"] } class Flight { Airport departureAirport Airport destinationAirport } 5.3 Many-to-many 51 . which means that the collection will be lazily initialized. The ORM DSL allows mapping unidirectional relationships using a foreign key association instead Grails will automatically inject a property of type java.title } The default fetch strategy used by Grails is "lazy".Set into the domain class based on the hasMany setting.1.table.
in this case Author.addToBooks(new Book(title:"The Stand")) . For example this will work and cascade saves: new Author(name:"Stephen King") .2. The owning side of the relationship.Grails supports many-to-many relationships by defining a hasMany on both sides of the relationship and having a belongsTo on the owned side of the relationship: class Book { static belongsTo = Author static hasMany = [authors:Author] String title } class Author { static hasMany = [books:Book] String name } Grails maps a many-to-many using a join table at the database level. just like Hibernate. You can alter various aspects of how the join table is mapped using the joinTable argument: 52 . takes responsibility for persisting the relationship and is the only side that can cascade saves across.addToBooks(new Book(title:"The Shining")) .save() However the below will only save the Book and not the authors! new Book(name:"Groovy in Action") .save() This is the expected behaviour as.1. Grails' Scaffolding feature does not currently support many-to-many relationship and hence you must write the code to manage the relationship yourself 5. GORM also supports mapping of basic collection types. For example. only one side of a many-to-many can take responsibility for managing the relationship. the following class creates a nicknames association that is a Set of String instances: class Person { static hasMany = [nicknames:String] } GORM will map an association like the above using a join table.addToAuthors(new Author(name:"Dierk Koenig")) .addToAuthors(new Author(name:"Guillaume Laforge")) .4 Basic Collection Types As well as associations between different domain classes.
For example: 53 . If you don't want this to happen use Groovy's ability to define multiple classes per file and include the Address class below the Person class in the grails-app/domain/Person.2. For example: class Person { Address homeAddress Address workAddress static embedded = ['homeAddress'.2 Composition in GORM As well as association. 'workAddress'] } class Address { String number String code } The resulting mapping would looking like this: If you define the Address class in a separate Groovy file in the grails-app/domain directory you will also get an address table. key: 'person_id'.3 Inheritance in GORM GORM supports inheritance both from abstract base classes and concrete persistent GORM entities.groovy file 5.2.class Person { static hasMany = [nicknames:String] static mapping = { hasMany joinTable: [name: 'bunch_o_nicknames'. In this case instead of mapping classes onto separate tables a class can be "embedded" within the current table. Grails supports the notion of composition. column: 'nickname'. type: "text"] } } The example above will map to a table that looks like the following: bunch_o_nicknames Table --------------------------------------------| person_id | nickname | --------------------------------------------| 1 | Fred | --------------------------------------------- 5.
util.Comparable in your Book class: 54 .4 Sets. don't abuse it and don't make your inheritance hierarchy too deep. Considerations At the database level Grails by default uses table-per-hierarchy mapping with a discriminator column called class so the parent class (Content) and its sub classes (BlogEntry. In general our advice is if you're going to use inheritance. Book etc.2.util. An alternative is to use table-per-subclass which can be enabled via the ORM DSL However. books and pod casts content = Content.).util. Table-per-hierarchy mapping has a down side in that you cannot have non-nullable properties with inheritance mapping.class Content { String author } class BlogEntry extends Content { URL url } class Book extends Content { String ISBN } class PodCast extends Content { byte[] audioStream } In the above example we have a parent Content class and then various child classes with more specific behaviour.list() // list only pod casts 5. The problem with this is there is no ordering when accessing the collection. Lists and Maps Sets of objects By default when you define a relationship with GORM it is a java. excessive use of inheritance and table-per-subclass can result in poor query performance due to the excessive use of join queries. Polymorphic Queries The upshot of inheritance is that you get the ability to polymorphically query. To get custom ordering you can say that the set is a SortedSet: class Author { SortedSet books static hasMany = [books:Book] } In this case a java.lang. share the same table.findAllByAuthor('Joe Bloggs') // find all by author def podCasts = PodCast.Set. which may not be what you want.SortedSet implementation is used which means you have to implement java.list() // list all blog entries.Set which is an unordered collection that cannot contain duplicates. In other words when you have: class Author { static hasMany = [books:Book] } The books property that GORM injects is a java. For example using the list method on the Content super class will return all sub classes of Content: def content = Content.
addToBooks(book) // Do it this way instead. When using a List.save() author.books = ["1590597583":"Grails Book"] a.save() In this case the key and value of the map MUST be strings.compareTo(obj.HibernateException: null index column for collection): // This won't work! def book = new Book(title: 'The Shining') book. elements must be added to the collection before being saved.class Book implements Comparable { String title Date releaseDate = new Date() int compareTo(obj) { releaseDate.books[0] // get the first book The way this works at the database level is Hibernate creates a books_idx column where it saves the index of the elements in the collection in order to retain this order at the db level.releaseDate) } } The result of the above class is that the Book instances in the books collections of the Author class will be ordered by their release date.save() Maps of Objects If you want a simple map of string/value pairs GORM can map this with the following: class Author { Map books // map of ISBN:book names } def a = new Author() a. Lists of objects If you simply want to be able to keep objects in the order which they were added and to be able to reference them by index like an array you can define your collection type as a List: class Author { List books static hasMany = [books:Book] } In this case when you add new elements to the books collection the order is retained in a sequential list indexed from 0 so you can do: author.addToBooks(book) author. otherwise Hibernate will throw an exception (org.hibernate. def book = new Book(title: 'Misery') author. If you want a Map of objects then you can do this: 55 .
since Hibernate needs to load the entire association in-order to maintain order.author = author book.get(1) p. This is typically done for you automatically by Grails.class Book { Map authors static hasMany = [authors:Author] } def a = new Author(name:"Stephen King") def book = new Book() book. 5. This allows you to use the save and delete methods as well as other GORM methods transparently. For example consider the following code: def book = new Book(title:"New Grails Book") def author = Author. The keys for the map must be strings.authors = [stephen:a] book. which manages your Hibernate session.get(1) author. A Note on Collection Types and Performance The Java Set type is a collection that doesn't allow duplicates.save() A major difference with Hibernate is when you call save it does not necessarily perform any SQL operations at that point.addToBooks(book) author. Grails automatically binds a Hibernate session to the currently executing request. in Hibernate terminology.1 Saving and Updating An example of using the save method can be seen below: def p = Person.3 Persistence Basics A key thing to remember about Grails is that under the surface Grails is using Hibernate for persistence. In order to ensure uniqueness when adding an entry to a Set association Hibernate has to load the entire associations from the database. Hibernate typically batches up SQL statements and executes them at the end. If you have a large numbers of entries in the association this can be costly in terms of performance. however.3. If you are coming from a background of using ActiveRecord or iBatis Hibernate's "session" model may feel a little strange. Therefore it is recommended that if you anticipate a large numbers of records in the association that you make the association bidirectional so that the link can be created on the inverse side. when you may want to control when those statements are executed or. There are occasions.save() 5.save() The static hasMany property defines the type of the elements within the Map.get(1) book. To do so you can use the flush argument to the save method: 56 . when the session is "flushed". The same behavior is required for List types. Given an Author with a large number of associated Book instances if you were to write code like the following you would see an impact on performance: def book = new Book(title:"New Grails Book") def author = Author. Essentially.save() In this example the association link is being created by the child (Book) and hence it is not necessary to manipulate the collection directly resulting in fewer queries and more efficient code.
2 Deleting Objects An example of the delete method can be seen below: def p = Person.get(1) p. although this is normally down to a programming or schema error. If you really need to batch delete data you can use the executeUpdate method to do batch DML statements: Customer. The key part to 57 .delete(flush:true) } catch(org.DataIntegrityViolationException e) { flash.get(1) try { p. [oldName:"Fred"]) 5.get(1) try { p. The following example shows how to catch a DataIntegrityViolationException that is thrown when you violate the database constraints: def p = Person.get(1) p.delete(flush:true) Using the flush argument will also allow you to catch any errors that may potentially occur during a delete.name = :oldName".a must read! 5.get(1) p.save(flush:true) } catch(Exception e) { // deal with exception } You can find out more about the subtleties of saving data in this article .3.3.id) } Note that Grails does not supply a deleteAll method as deleting data is discouraged and can often be avoided through boolean flags/logic.springframework.save(flush:true) Note that in this case all pending SQL statements including previous saves will be synchronized with the db. if you want to perform the delete in place then you can use the flush argument: def p = Person.dao. This also allows you to catch any exceptions thrown.delete() By default Grails will use transactional write behind to perform the delete. id:p.3 Understanding Cascading Updates and Deletes It is critical that you understand how cascading updates and deletes work when using GORM.name}" redirect(action:"show".message = "Could not delete person ${p.executeUpdate("delete Customer c where c.def p = Person. which is typically useful in highly concurrent scenarios involving optimistic locking: def p = Person. A common error that may occur is if you violate a database constraint.
one-to-many or many-to-many if you define belongsTo updates and deletes will cascade from the owning class to its possessions (the other side of the relationship). if I were to remove belongsTo then the above cascading deletion code would not work. Whether it is a one-to-one. Unidirectional one-to-many class A { static hasMany = [bees:B] } class B { } In the case of a unidirectional one-to-many where the many side defines no belongsTo then the cascade strategy is set to "SAVE-UPDATE". Here is an example: class Airport { String name static hasMany = [flights:Flight] } class Flight { String number static belongsTo = [airport:Airport] } If I now create an Airport and add some Flights to it I can save the Airport and have the updates cascaded down to each flight. To understand this better take a look at the summaries below that describe the default behaviour of GORM with regards to specific associations.addToFlights(new Flight(number:"EZ0938")) .findByName("Gatwick") airport. hence saving the whole object graph: new Airport(name:"Gatwick") . Bidirectional one-to-many no belongsTo class A { static hasMany = [bees:B] } class B { A a } 58 . Bidirectional one-to-many with belongsTo class A { static hasMany = [bees:B] } class B { static belongsTo = [a:A] } In the case of a bidirectional one-to-many where the many side defines a belongsTo then the cascade strategy is set to "ALL" for the one side and "NONE" for the many side. Also read part 2 of the GORM Gotchas series of articles to get a deeper understanding of relationships and cascading.remember is the belongsTo setting which controls which class "owns" a relationship.delete() However.save() Conversely if I later delete the Airport all Flights associated with it will also be deleted: def airport = Airport. If you do not define belongsTo then no cascades will happen and you will have to manually save each object.addToFlights(new Flight(number:"BA3430")) .
destination. You can also use fetch: 'join' instead of lazy: false . but you need to be careful with one-to-manys. At that point.findByName("Gatwick") airport. you will likely end up with fewer 59 . Configuring Eager Fetching An alternative approach that avoids the N+1 queries is to use eager fetching. Unidirectional One-to-one with belongsTo class A { } class B { static belongsTo = [a:A] } In the case of a unidirectional one-to-one association that defines a belongsTo then the cascade strategy is set to "ALL" for the owning side of the relationship (A->B) and "NONE" from the side that defines the belongsTo (B->A) Note that if you need further control over cascading behaviour.4 Eager and Lazy Fetching Associations in GORM are by default lazy.In the case of a bidirectional one-to-many where the many side does not define a belongsTo then the cascade strategy is set to "SAVE-UPDATE" for the one side and "NONE" for the many side. This is best explained by example: class Airport { String name static hasMany = [flights:Flight] } class Flight { String number Location destination static belongsTo = [airport:Airport] } class Location { String city String country } Given the above domain classes and the following code: def airport = Airport.city } GORM will execute a single SQL query to fetch the Airport instance. Queries will work as you'd expect right up to the moment you add a limit to the number of results you want. another to get its flights. 5. although a second query will be executed to fetch the collection. in which case GORM will only execute a single query to get the airports and their flights.3. and then 1 extra query for each iteration over the flights association to get the current flight's destination.each { println it. which can be specified as follows: class Airport { String name static hasMany = [flights:Flight] static mapping = { flights lazy: false } } In this case the flights association will be loaded at the same time as its Airport instance. This works well for single-ended associations. you can use the ORM DSL. In other words you get N+1 queries (if you exclude the original one to get the airport).flights.
The version column gets read into a version property that contains the current versioned state of persistent instance which you can access: def airport = Airport. For example if you had an Airport that had 30 flights. This requires flushing the session: 60 . due to the batchSize argument. The downside is that you have to deal with this exception if you have highly concurrent writes. In other words. You can find more information on the mapping options in the section on the ORM DSL. Using Batch Fetching Although eager fetching is appropriate for some cases. it is not always desirable. This is useful as it allows a certain level of atomicity without resorting to pessimistic locking that has an inherit performance penalty. Batch fetching can also be configured at the class level as follows: class Flight { … static mapping = { batchSize 10 } } Check out part 3 of the GORM Gotchas series for more in-depth coverage of this tricky topic. So. 5. Optimistic locking essentially is a feature of Hibernate which involves storing a version number in a special version column in the database. With batch fetching you get 1 query to fetch the Airport and 3 queries to fetch each Flight in batches of 10. if you didn't configure batch fetching you would get 1 query to fetch the Airport and then 30 queries to fetch each flight. An alternative to eager fetching is to use batch fetching.results than you were expecting. If you made everything eager you could quite possibly load your entire database into memory resulting in performance and memory problems. the recommendation is currently to use fetch: 'join' for single-ended associations and lazy: false for one-to-manys.get(10) println airport. For example: class Airport { String name static hasMany = [flights:Flight] static mapping = { flights batchSize:10 } } In this case. Be careful how and where you use eager loading because you could load your entire database into memory with too many eager associations. when you iterate over the flights association.version When you perform updates Hibernate will automatically check the version property against the version column in the database and if they differ will throw a StaleObjectException and the transaction will be rolled back. batch fetching is an optimization of the lazy fetching strategy. Hibernate will fetch results in batches of 10. you can configure Hibernate to lazily fetch results in "batches".5 Pessimistic and Optimistic Locking Optimistic Locking By default GORM classes are configured for optimistic locking. Essentially. The reason for this is quite technical but ultimately the problem arises from GORM using a left outer join.3.
dao.6 Modification Checking 61 . For example using a dynamic finder: def airport = Airport..OptimisticLockingFailureException e) { // deal with exception } The way you deal with the exception depends on the application.. in the above case what we are doing is "upgrading" from a regular SELECT to a SELECT.FOR UPDATE and another thread could still have updated the record in between the call to get() and the call to lock(). supports pessimistic locking.springframework.save() Grails will automatically deal with releasing the lock for you once the transaction has been committed. the embedded HSQLDB shipped with Grails which is used as the default in-memory database does not.get { eq('name'.name = "Heathrow" airport.save() In this case only SELECT. To get around this problem you can use the static lock method that takes an id just like get: def airport = Airport.get(10) try { airport.name = "Heathrow" airport.createCriteria(). [lock:true]) Or using criteria: def airport = Airport.def airport = Airport. Though Grails. if it becomes a problem you can resort to pessimistic locking. However.get(10) airport.findByName("Heathrow".lock() // lock for update airport. 'Heathrow') lock true } 5. Alternatively.save(flush:true) } catch(org.lock(10) // lock for update airport.name = "Heathrow" airport. As well as the lock method you can also obtain a pessimistic locking using queries. In Grails pessimistic locking is performed on an existing instance via the lock method: def airport = Airport. Pessimistic Locking Pessimistic locking is equivalent to doing a SQL "SELECT * FOR UPDATE" statement and locking a row in the database. If you need to test pessimistic locking you will need to do so against a database that does have support such as MySQL.FOR UPDATE is issued. This has the implication that other read operations will be blocking until the lock is released. You could attempt a programmatic merge of the data or go back to the user and ask them to resolve the conflict. through Hibernate.3.
getDirtyPropertyNames() for (fieldName in modifiedFieldNames) { // do something based on changed value } getPersistentValue You can use the getPersistentValue method to retrieve the value of a modified field: def airport = Airport.isDirty('name')) { // do something based on changed name } getDirtyPropertyNames You can use the getDirtyPropertyNames method to retrieve the names of modified fields. this may be empty but will not be null: def airport = Airport.properties = params if (airport.get(10) assert !airport."$fieldName" def originalValue = airport.4 Querying with GORM GORM supports a number of powerful ways to query from dynamic finders.get(10) assert !airport.isDirty() airport. So GORM provides some methods to retrieve the original values that Hibernate caches when it loads the instance (which it uses for dirty checking).get(10) assert !airport.properties = params if (airport. findAll and so on combined with GORM results in a powerful combination.get(10) assert !airport. isDirty You can use the isDirty method to check if any field has been modified: def airport = Airport. Listing instances 62 .properties = params def modifiedFieldNames = airport.Once you have loaded and possibly modified a persistent domain class instance. However. to criteria to Hibernate's object oriented query language HQL.isDirty() airport. let's start with the basics. Reloading using another query would trigger a flush which could cause problems if your data isn't ready to be flushed yet. If you try to reload the instance using get Hibernate will return the current modified instance from its Session cache.getDirtyPropertyNames() for (fieldName in modifiedFieldNames) { def currentValue = airport.isDirty() airport.properties = params def modifiedFieldNames = airport. it isn't straightforward to retrieve the original values.isDirty()) { // do something based on changed state } You can also check if individual fields have been modified: def airport = Airport.isDirty() airport. Groovy's ability to manipulate collections via GPath and methods like sort.getPersistentValue(fieldName) if (currentValue != originalValue) { // do something based on changed value } } 5.
list(offset:10.4. secondDate ) book = Book.getAll(23. Retrieval by Database Identifier The second basic form of retrieval is by database identifier using the get method: def book = Book.findByReleaseDateBetween( firstDate. Instead. Take for example the Book class: class Book { String title Date releaseDate Author author } class Author { String name } The Book class has properties such as title. 93. based on the properties of a given class. max:20) as well as sorting: def books = Book. a method is auto-magically generated using code synthesis at runtime. order:"asc") Here.findByReleaseDateGreaterThan( someDate ) book = Book.If you simply need to obtain all the instances of a given class you can use the list method: def books = Book. the sort argument is the name of the domain class property that you wish to sort on. someDate ) 63 . but the methods themselves don't actually exist in any form at the code level. and the order argument is either asc for ascending or desc for descending. releaseDate and author.findByTitle("The Stand") book = Book.findByTitleLike("Harry Pot%") book = Book.list(sort:"title". These can be used by the findBy and findAllBy methods in the form of "method expressions": def book = Book.list() The list method supports arguments to perform pagination: def books = Book.findByTitleLikeOrReleaseDateLessThan( "%Something%".1 Dynamic Finders GORM supports the concept of dynamic finders. 81) 5.get(23) You can also obtain a list of instances for a set of identifiers using getAll: def books = Book. A dynamic finder looks like a static method invocation.
e.findByTitleLike("Harry Pot%") In the above example the first query is equivalent to equality whilst the latter.findByTitle("The Stand") book = Book. except case insensitive NotEqual . but you could equally use Or: def books = Book.findByReleaseDateBetween( lastWeek.Similar to a Like. Querying Associations Associations can also be used within queries: 64 . If you need to use more. due to the Like comparator. you can only use dynamic finders with a maximum of two criteria.Negates equality Between . the method name can only have one boolean operator.In the list of given values LessThan . new Date()-30) At the moment. The basic form is: Book. as demonstrated in the following example: def now = new Date() def lastWeek = now .Is a null value (doesn't require an argument) Notice that the last 3 require different numbers of method arguments compared to the rest.findAllByReleaseDateIsNotNull() Boolean logic (AND/OR) Method expressions can also use a boolean operator to combine two criteria: def books = Book.less than the given value LessThanEquals . is equivalent to a SQL like expression. Each comparator changes the nature of the query. new Date()-30) In this case we're using And in the middle of the query to make sure both conditions are satisfied. you should consider using either Criteria or the HQL.7 def book = Book.findAllByTitleLikeAndReleaseDateGreaterThan("%Java%". The possible comparators include: InList . For example: def book = Book.greater than a given value GreaterThanEquals .findAllByReleaseDateIsNull() books = Book.Not a null value (doesn't require an argument) IsNull .Method Expressions A method expression in GORM is made up of the prefix such as findBy followed by an expression that combines one or more properties.Equivalent to a SQL like expression Ilike .findBy([Property][Comparator][Boolean Operator])?[Property][Comparator] The tokens marked with a '?' are optional.findAllByTitleLikeOrReleaseDateGreaterThan("%Java%". now ) books = Book.greater than or equal a given value Like .Between two values (requires two arguments) IsNotNull .less than or equal a give value GreaterThan . i.
Criteria can be used either via the createCriteria or withCriteria methods. The builder uses Hibernate's Criteria API. order:"desc"]) 5. "Barney%") } maxResults(10) order("holderLastName". It is a much better alternative to using StringBuffer. sort:"title". "London") } 65 . 500. Conjunctions and Disjunctions As demonstrated in the previous example you can group criteria in a logical OR using a or { } block: or { between("balance".def author = Author. "Fred%") like("holderFirstName". 1000) eq("branch".findAllByAuthor(author) : [] In this case if the Author instance is not null we use it in a query to obtain all the Book instances for the given Author.4. 1000) eq("branch". "London") } This also works with logical AND: and { between("balance". the nodes on this builder map the static methods found in the Restrictions class of the Hibernate Criteria API. Example Usage: def c = Account.findByName("Stephen King") def books = author ? Book. 500. 500. 1000) eq("branch". advanced way to query that uses a Groovy builder to construct potentially complex queries.2 Criteria Criteria is a type safe. offset:2. "desc") } This criteria will select up to 10 Account objects matching the following criteria: balance is between 500 and 1000 branch is 'London' holderFirstName starts with 'Fred' or 'Barney' The results will be sorted in descending ordery by holderLastName. [max:3.createCriteria() def results = c { between("balance". "London") or { like("holderFirstName". Pagination & Sorting The same pagination and sorting parameters available on the list method can also be used with dynamic finders by supplying a map as the final parameter: def books = Book.findAllByTitleLike("Harry Pot%".
createCriteria() def now = new Date() def results = c.list { or { between('created'. For example say the Account class had many Transaction objects: class Account { … static hasMany = [transactions:Transaction] … } We can query this association by using the property name transaction as a builder node: def c = Account. You can also nest such association queries within logical blocks: def c = Account.now-10. To use projections you need to define a "projections" node within the criteria builder tree. now) } } } Here we find all accounts that have either performed transactions in the last 10 days OR have been recently created in the last 10 days. Querying with Projections Projections may be used to customise the results. There are equivalent methods within the projections node to the methods found in the Hibernate Projections class: def c = Account. Querying Associations Associations can be queried by having a node that matches the property name. 1000) eq("branch".now-10.createCriteria() def now = new Date() def results = c. "London") } All top level conditions are implied to be AND'd together.list { transactions { between('date'.And you can also negate using logical NOT: not { between("balance".now) transactions { between('date'.createCriteria() def numberOfBranches = c. now) } } The above code will find all the Account instances that have performed transactions within the last 10 days. 500.get { projections { countDistinct('branch') } } 66 .now-10.
The Person class may have a property named firstName which is mapped to a column in the database named first_name.list { maxResults(10) firstResult(50) fetchMode("aRelationship".last() def n = results. Using Scrollable Results You can use Hibernate's ScrollableResults feature by calling the scroll method: def results = crit. 'asc' } 67 .first() def l = results. The first_name attribute referenced in the example relates to the persistence model. this can also be achieved using a criteria query: def criteria = Task.id". Contrary to JDBC. not the object model. The Query / ScrollableResults pattern is very similar to the JDBC PreparedStatement/ ResultSet pattern and the semantics of methods of this interface are similar to the similarly named methods on ResultSet.Using SQL Restrictions You can access Hibernate's SQL Restrictions capabilities.getLong('number') To quote the documentation of Hibernate ScrollableResults: A result iterator that allows moving around within the results by arbitrary increments.scroll(10) def accountNumber = results. def c = Person.JOIN) } Querying with Eager Fetching In the section on Eager and Lazy Fetching we discussed how to declaratively specify fetching to avoid the N+1 SELECT problem. Also note that the SQL used here is not necessarily portable across databases.hibernate.assignee. FM.scroll { maxResults(10) } def f = results.list { sqlRestriction "char_length( first_name ) <= 4" } Note that the parameter there is SQL. Setting properties in the Criteria instance If a node within the builder tree doesn't match a particular criterion it will attempt to set a property on the Criteria object itself.createCriteria() def peopleWithShortFirstNames = c. The below example calls setMaxResults and setFirstResult on the Criteria instance: import org. columns of results are numbered from zero.id join 'assignee' join 'project' order 'priority'.FetchMode as FM … def results = c.createCriteria() def tasks = criteria.next() def p = results. Thus allowing full access to all the properties in this class. task.list{ eq "assignee.previous() def future = results. However.
This method is not to be confused with a limit to just the first row. ["The Shi%"]) 68 .title like ?". count Returns the number of matching rows. Returns a scrollable result set. Instead. If subqueries or associations are used. this allows listing only distinct entities and is equivalent to DISTINCT_ROOT_ENTITY of the CriteriaSpecification class. just one row.4.findAll("from Book as b where b. GORM provides a number of methods that work with HQL including find. Method Reference If you invoke the builder with no method name such as: c { … } The build defaults to listing all the results and hence the above is equivalent to: c. FM. findAll and executeQuery.e.FetchMode as FM … def results = Airport. use the 'select' fetch mode: import org.list { … } Method list get scroll Description This is the default method. HQL: The Hibernate Query Language of the Hibernate documentation. one may end up with the same row multiple times in the result listDistinct set.Notice the usage of the join method: it tells the criteria API to use a JOIN to fetch the named associations with the Task instances. because you will most likely end up with duplicate results. An example of a query can be seen below: def results = Book. i. Returns a unique result set.SELECT } Although this approach triggers a second query to get the flights association.hibernate. that it only queries one row.even with the maxResults option.withCriteria { eq("region". "EMEA") fetchMode "flights". you will get reliable results .3 Hibernate Query Language (HQL) GORM classes also support Hibernate's query language HQL.title like 'Lord of the%'") Positional and Named Parameters In this case the value passed to the query is hard coded.findAll("from Book as b where b. however you can equally use positional parameters: def results = Book. The criteria has to be formed that way. It's probably best not to use this for one-to-many associations though. It returns all matching rows. a very complete reference for which can be found Chapter 14. 5.
The following is a list of supported events: beforeInsert .findByName("Stephen King") def books = Book.Executed when an object is loaded from the database To add an event simply register the relevant closure with your domain class.findAll("from Book as book where book.title asc".findAll("from Book as b where b.findAll("from Book as book where book.title like 'Lord of the%' order by b.Executed after an object has been updated onLoad .author = ?". To do so simply specify the pagination options as a map at the end of the method call and include an "ORDER BY" clause in the HQL: def results = Book.author = :author".Executed before an object is deleted afterInsert .1 Events and Auto Timestamping GORM supports the registration of events as methods that get fired when certain events occurs such as deletes. 5.Executed after an object is persisted to the database afterUpdate . [max:10.findByName("Stephen King") def books = Book.surname = ?".Executed before an object is initially persisted to the database beforeUpdate . inserts and updates.findAll("\ from Book as b.author like :search". [search:"The Shi%"]) def author = Author.findAll("from Book as b where b. offset:20]) 5.author = a and a.5. [author: author]) Multiline Queries If you need to separate the query across multiple lines you can use a line continuation character: def results = Book.Executed after an object has been updated afterDelete . [author]) Or even named parameters: def results = Book. ['Smith']) Groovy multiline strings will NOT work with HQL queries Pagination and Sorting You can also perform pagination and sorting whilst using HQL queries.5 Advanced GORM Features The following sections cover more advanced usages of GORM including caching. 69 . custom mapping and events.title like :search or b.def author = Author. \ Author as a \ where b.Executed before an object is updated beforeDelete .
The onLoad event Fired when an object is loaded from the db: 70 .withNewSession { new ActivityTrace(eventName:"Person Deleted".save(flush:true)).Do not attempt to flush the session within an event (such as with obj. Event types The beforeInsert event Fired before an object is saved to the db class Person { Date dateCreated def beforeInsert() { dateCreated = new Date() } } The beforeUpdate event Fired before an existing object is updated class Person { Date dateCreated Date lastUpdated def beforeInsert() { dateCreated = new Date() } def beforeUpdate() { lastUpdated = new Date() } } The beforeDelete event Fired before an object is deleted. Since events are fired during flushing this will cause a StackOverflowError. class Person { String name Date dateCreated Date lastUpdated def beforeDelete() { ActivityTrace. Fortunately the withNewSession method allows you to share the same transactional JDBC connection even though you're using a different underlying Session. Since events are triggered whilst Hibernate is flushing using persistence methods like save() and delete() won't result in objects being saved unless you run your operations with a new Session.data:name).save() } } } Notice the usage of withNewSession method above.
or one concrete class per interface. You can use one class that implements all of the required interfaces.groovy or in the doWithSpring closure in a plugin descriptor by registering a Spring bean named hibernateEventListeners. listenerMap which specifies the listeners to register for various Hibernate events. or any combination. The values of the map are instances of classes that implement one or more Hibernate listener interfaces. The valid map keys and corresponding interfaces are listed here: 71 . This bean has one property.class Person { String name Date dateCreated Date lastUpdated def onLoad() { name = "I'm loaded" } } Custom Event Listeners You can also register event handler classes in an application's grails-app/conf/spring/resources.
and PostDeleteEventListener using the following in an application: 72 .Name auto-flush merge create create-onflush delete dirty-check evict flush flush-entity load load-collection lock refresh replicate save-update save update pre-load pre-update pre-delete pre-insert Interface AutoFlushEventListener MergeEventListener PersistEventListener PersistEventListener DeleteEventListener DirtyCheckEventListener EvictEventListener FlushEventListener FlushEntityEventListener LoadEventListener InitializeCollectionEventListener LockEventListener RefreshEventListener ReplicateEventListener SaveOrUpdateEventListener SaveOrUpdateEventListener SaveOrUpdateEventListener PreLoadEventListener PreUpdateEventListener PreDeleteEventListener PreInsertEventListener pre-collection-recreate PreCollectionRecreateEventListener pre-collection-remove pre-collection-update post-load post-update post-delete post-insert post-commit-update post-commit-delete post-commit-insert PreCollectionRemoveEventListener PreCollectionUpdateEventListener PostLoadEventListener PostUpdateEventListener PostDeleteEventListener PostInsertEventListener PostUpdateEventListener PostDeleteEventListener PostInsertEventListener post-collection-recreate PostCollectionRecreateEventListener post-collection-remove PostCollectionRemoveEventListener post-collection-update PostCollectionUpdateEventListener For example. you could register a class AuditEventListener which implements PostInsertEventListener. PostUpdateEventListener.
'post-update':auditListener. static mapping = { } } 5.5.1 Table and Column Names Table names The database table name which the class maps to can be customized using a call to table: 73 .2.2 Custom ORM Mapping Grails domain classes can be mapped onto many legacy schemas via an Object Relational Mapping Domain Specify Language. 'post-update':auditListener.beans = { auditListener(AuditEventListener) hibernateEventListeners(HibernateEventListeners) { listenerMap = ['post-insert':auditListener.. column names and so on. By merely defining a lastUpdated and dateCreated property these will be automatically updated for you by GORM.5. The following sections takes you through what is possible with the ORM DSL. 'post-delete':auditListener] } } Automatic timestamping The examples above demonstrated using events to update a lastUpdated and dateCreated property to keep track of updates to objects. this is actually not necessary. 'post-delete':auditListener] } } or use this in a plugin: def doWithSpring = { auditListener(AuditEventListener) hibernateEventListeners(HibernateEventListeners) { listenerMap = ['post-insert':auditListener. However. You only needs this functionality if you need to in anyway tailor the way GORM maps onto legacy schemas or performs caching Custom mappings are defined using a a static mapping block defined within your domain class: class Person { . None if this is necessary if you are happy to stick to the conventions defined by GORM for table. If this is not the behaviour you want you can disable this feature with: class Person { Date dateCreated Date lastUpdated static mapping = { autoTimestamp false } } 5.
class Person { . static mapping = { table 'people' } } In this case the class would be mapped to a table called people instead of the default name of person.hibernate. In the case of a one-to-one association this is exactly the same as any regular column. One-to-One Mapping In the case of associations it is also possible to change the foreign keys used to map associations.. For example consider the below: 74 . which allows complete customization of how a type is persisted. Column names It is also possible to customize the mapping for individual columns onto the database. For example if its the name you want to change you can do: class Person { String firstName static mapping = { table 'people' firstName column:'First_Name' } } In this case we define method calls that match each property name (in this case firstName).UserType class. We then use the named parameter column. See the Hibernate documentation regarding Basic Types for further information.usertype. to specify the column name to map onto. This includes specifing user types that subclass the Hibernate org. As an example if you had a PostCodeType you could use it as follows: class Address { String number String postCode static mapping = { postCode type:PostCodeType } } Alternatively if you just wanted to map it to one of Hibernate's basic types other than the default chosen by Grails you could use: class Address { String number String postCode static mapping = { postCode type:'text' } } This would make the postCode column map to the SQL TEXT or CLOB type depending on which database is being used. Column type GORM supports configuration of Hibernate types via the DSL using the type attribute.
However. key:'Person_Id'. column:'Address_Id'] } } Many-to-Many Mapping Grails. but instead some intermediate join table you can use the joinTable parameter: class Person { String firstName static hasMany = [addresses:Address] static mapping = { table 'people' firstName column:'First_Name' addresses joinTable:[name:'Person_Addresses'. with unidirectional association the foreign key needs to be specified on the association itself. For example consider the below many-to-many association: class Group { … static hasMany = [people:Person] } class Person { … static belongsTo = Group static hasMany = [groups:Group] } In this case Grails will create a join table called group_person containing foreign keys called person_id and group_id referencing the person and group tables. If you need to change the column names you can specify a column within the mappings for each class. by default maps a many-to-many association using a join table.class Person { String firstName Address address static mapping = { table 'people' firstName column:'First_Name' address column:'Person_Adress_Id' } } By default the address association would map to a foreign key column called address_id. One-to-Many Mapping With a bidirectional one-to-many you can change the foreign key column used simple by changing the column name on the many side of the association as per the example in the previous section on one-to-one associations. For example given a unidirectional one-to-many relationship between Person and Address the following code will change the foreign key in the address table: class Person { String firstName static hasMany = [addresses:Address] static mapping = { table 'people' firstName column:'First_Name' addresses column:'Person_Address_Id' } } If you don't want the column to be in the address table. 75 . By using the above mapping we have changed the name of the foreign key column to Person_Adress_Id.
class Group { … static mapping = { people column:'Group_Person_Id' } } class Person { … static mapping = { groups column:'Group_Group_Id' } }
You can also specify the name of the join table to use:
class Group { … static mapping = { people column:'Group_Person_Id',joinTable:'PERSON_GROUP_ASSOCIATIONS' } } class Person { … static mapping = { groups column:'Group_Group_Id',joinTable:'PERSON_GROUP_ASSOCIATIONS' } }
126.96.36.199 Caching Strategy
Setting up caching Hibernate features a second-level cache with a customizable cache provider. This needs to be configured in the grails-app/conf/DataSource.groovy file as follows:
hibernate { cache.use_second_level_cache=true cache.use_query_cache=true cache.provider_class='org.hibernate.cache.EhCacheProvider' }
You can of course customize these settings how you desire, for example if you want to use a distributed caching mechanism.
For further reading on caching and in particular Hibernate's second-level cache, refer to the Hibernate documentation on the subject.
Caching instances In your mapping block to enable caching with the default settings use a call to the cache method:
class Person { .. static mapping = { table 'people' cache true } }
This will configure a 'read-write' cache that includes both lazy and non-lazy properties. If you need to customize this further you can do:
class Person { .. static mapping = { table 'people' cache usage:'read-only', include:'non-lazy' } }
Caching associations As well as the ability to use Hibernate's second level cache to cache instances you can also cache collections (associations) of objects. For example:
class Person { String firstName static hasMany = [addresses:Address] static mapping = { table 'people' version false addresses column:'Address', cache:true } } class Address { String number String postCode }
This will enable a 'read-write' caching mechanism on the addresses collection. You can also use:
cache:'read-write' // or 'read-only' or 'transactional'
To further configure the cache usage. Caching Queries You can cache queries such as dynamic finders and criteria. To do so using a dynamic finder you can pass the cache argument:
def person = Person.findByFirstName("Fred", [cache:true])
Note that in order for the results of the query to be cached, you still need to enable caching in your mapping as discussed in the previous section.
You can also cache criteria queries:
def people = Person.withCriteria { like('firstName', 'Fr%') cache true }
Cache usages Below is a description of the different cache settings and their usages: read-only - If your application needs to read but never modify instances of a persistent class, a read-only cache may be used. read-write - If the application needs to update data, a read-write cache might be appropriate.
nonstrict-read-write - If the application only occasionally needs to update data (ie. if it is extremely unlikely that two transactions would try to update the same item simultaneously) and strict transaction isolation is not required, a nonstrict-read-write cache might be appropriate. transactional - The transactional cache strategy provides support for fully transactional cache providers such as JBoss TreeCache. Such a cache may only be used in a JTA environment and you must specify hibernate.transaction.manager_lookup_class in the grails-app/conf/DataSource.groovy file's hibernate config.
184.108.40.206 Inheritance Strategies
By default GORM classes uses table-per-hierarchy inheritance mapping. This has the disadvantage that columns cannot have a NOT-NULL constraint applied to them at the db level. If you would prefer to use a table-per-subclass inheritance strategy you can do so as follows:
class Payment { Long id Long version Integer amount static mapping = { tablePerHierarchy false } } class CreditCardPayment extends Payment String cardNumber }
The mapping of the root Payment class specifies that it will not be using table-per-hierarchy mapping for all child classes.
184.108.40.206 Custom Database Identity
You can customize how GORM generates identifiers for the database using the DSL. By default GORM relies on the native database mechanism for generating ids. This is by far the best approach, but there are still many schemas that have different approaches to identity. To deal with this Hibernate defines the concept of an id generator. You can customize the id generator and the column it maps to as follows:
class Person { .. static mapping = { table 'people' version false id generator:'hilo', params:[table:'hi_value',column:'next_value',max_lo:100] } }
In this case we're using one of Hibernate's built in 'hilo' generators that uses a separate table to generate ids.
For more information on the different Hibernate generators refer to the Hibernate reference documentation
Note that if you want to merely customise the column that the id lives on you can do:
class Person { .. static mapping = { table 'people' version false id column:'person_id' } }
220.127.116.11 Composite Primary Keys
GORM supports the concept of composite identifiers (identifiers composed from 2 or more properties). It is not an approach we recommend, but is available to you if you need it:
class Person { String firstName String lastName static mapping = { id composite:['firstName', 'lastName'] } }
The above will create a composite id of the firstName and lastName properties of the Person class. When you later need to retrieve an instance by id you have to use a prototype of the object itself:
def p = Person.get(new Person(firstName:"Fred", lastName:"Flintstone")) println p.firstName
220.127.116.11 Database Indices
To get the best performance out of your queries it is often necessary to tailor the table index definitions. How you tailor them is domain specific and a matter of monitoring usage patterns of your queries. With GORM's DSL you can specify which columns need to live in which indexes:
class Person { String firstName String address static mapping = { table 'people' version false id column:'person_id' firstName column:'First_Name', index:'Name_Idx' address column:'Address', index:'Name_Idx,Address_Index' } }
Note that you cannot have any spaces in the value of the index attribute; in this example index:'Name_Idx, Address_Index' will cause an error.
18.104.22.168 Optimistic Locking and Versioning
As discussed in the section on Optimistic and Pessimistic Locking, by default GORM uses optimistic locking and automatically injects a version property into every class which is in turn mapped to a version column at the database level. If you're mapping to a legacy schema this can be problematic, so you can disable this feature by doing the following:
class Person { .. static mapping = { table 'people' version false } }
one-to-one and many-to-one associations are by default lazy. you can use the same technique as for 80 . the other settings available are: 1. with one query per batch. batchSize: N where N is an integer. it could feasibly be the more expensive approach if your domain model and data result in more and larger results than would otherwise be necessary. For more advanced users. ensures that when a Person instance is loaded. You can find out more about these options in the Hibernate user guide and this primer on fetching strategies. Typically you will want to reduce the number of queries. Note that ORM DSL does not currently support the "subselect" fetching strategy. These allow you to fetch results in batches. If the associated entities also have non-lazy associations. but the most common ones are: lazy: false fetch: 'join' and they're used like this: class Person { String firstName Pet pet static hasMany = [addresses:Address] static mapping = { addresses lazy:false pet fetch: 'join' } } class Address { String street String postCode } class Pet { String name } The first option. GORM collections are lazily loaded by default but you can change this behaviour via the ORM DSL. lazy: false. except the collection is loaded via a JOIN rather than another SELECT. As a simple example. There are several options available to you.If you disable optimistic locking you are essentially on your own with regards to concurrent updates and are open to the risk of users losing (due to data overriding) data unless you use pessimistic locking 5. The second option is basically the same. lazy: false . the number of queries grows exponentially! If you want to make a one-to-one or many-to-one association non-lazy/eager. You can get the same behaviour with eager loading by combining batchSize with the lazy: false option. Lazy Single-Ended Associations In GORM. batchSize: N 2. Non-lazy single ended associations can be problematic when you load many entities because each non-lazy association will result in an extra SELECT statement. On the other hand. Hibernate will fetch that Pet plus the four next ones.5. so fetch: 'join' will be the more appropriate option. then when we access the first pet property.2.8 Eager and Lazy Fetching Lazy Collections As discussed in the section on Eager and Lazy fetching. consider this mapping for Person: class Person { String firstName Pet pet static mapping = { pet batchSize: 5 } } If a query returns multiple Person instances. its addresses collection is loaded at the same time with a second SELECT.
whenever you retrieve that Pet instance via a query. Unfortunately this technique can produce surprising results. The following code will work as you would expect: def person = Person. Fortunately for us.get(1) assert person. Once that happens. That means you don't have to worry at all about proxies in the majority of cases. Consider the following example classes: class Pet { String name } class Dog extends Pet { } class Person { String name Pet pet } and assume that we have a single Person instance with a Dog as his or her pet. Hibernate creates a proxy for its pet relation and attaches it to the session. 81 . The way this works is that Hibernate dynamically subclasses the proxied entity to create the proxy. or when you directly access the relation. But GORM doesn't do that for objects returned via a query that returns a list. Lazy Single-Ended Associations and Proxies In order to facilitate single-ended lazy associations Hibernate uses runtime generated proxies.list()[0] instanceof Dog For some reason. or the pet relation within the same session . Hibernate gives you the proxy. Hibernate will load the entity from the database. this will work: assert Pet. GORM automatically unwraps the proxy when you use get() and findBy*(). Consider the previous example but with a lazily-loaded person association: Hibernate will set the person property to a proxy that is a subclass of Person.get(person. such as list() and findAllBy*().petId) instanceof Dog But this won't: def person = Person. a get().get(1) assert person. When you call any of the getters or setters on that proxy.lazy collections: class Person { String firstName } class Address { String street String postCode static belongsTo = [person:Person] static mapping = { person lazy:false } } Here we configure GORM to load the associated Person instance (through the person property) whenever an Address is loaded. When you load the Person instance. To add to the confusion.pet instanceof Dog assert Pet. the second assertion fails.pet instanceof Dog assert Pet.list()[0] instanceof Dog What's going on here? It's down to a combination of how proxies work and the guarantees that the Hibernate session makes.
cascade ALL operations to associations all-delete-orphan .5.useful if a pessimistic lock should be cascaded to its associations refresh . the ORM DSL gives you complete access to Hibernate's transitive persistence capabilities via the cascade attribute. it won't help here casting is involved. Valid settings for the cascade attribute include: create .get(1) assert Pet.However.instanceOf(Dog) However.cascades only deletes to an association lock .cascades only saves and updates to an association delete .list()[0]. if Hibernate hasn't attached the proxy to the session.list()[0] Of course.cascades creation of new records from one association to another merge .get(1) Dog pet = Pet.hence why the last example works.merges the state of a detached association save-update . At least you will know why such an error occurs and be able to work around it.2. These days it's rare that you will come across this issue. the primary mechanism to control the way updates and deletes are cascading from one association to another is the belongsTo static property.cascades evictions (equivalent to discard() in GORM) to associations if set all . However. You can protect yourself to a degree from this problem by using the instanceOf method by GORM: def person = Person. If you use an untyped variable for the pet instead. the following code will throw a ClassCastException because the first pet in the list is a proxy instance with a class that is neither Dog nor a sub-class of Dog: def person = Person. 5.9 Custom Cascade Behaviour As describes in the section on cascading updates. it's best not to use static types in this situation. those queries will return the real instances . you can access any Dog properties or methods on the instance without any problems. Children are also deleted when the parent is. but it's best to be aware of it just in case.5. For example. It is advisable to read the section in the Hibernate documentation on transitive persistence to obtain a better understanding of the different cascade styles and recommendation for their usage To specific the cascade attribute simply define one or many (comma-separated) of the aforementioned settings as its value: class Person { String firstName static hasMany = [addresses:Address] static mapping = { addresses cascade:"all-delete-orphan" } } class Address { String street String postCode } 5.10 Custom Hibernate Types 82 .Applies only to one-to-many associations and indicates that when a child is removed from an association then it should be automatically deleted.2.cascades refreshes to an association evict .
unique: true The column definitions do not support the following attributes: type. You can achieve a similar effect via Hibernate's custom user types. Let's start by taking a look at a simple domain class that uses an old-fashioned (pre-Java 1. but what happens if you have a legacy database that uses a different SQL type for one of the columns? In that case. { column name: "first_name" column name: "last_name" } rating type: RatingUserType } } The above example will create "first_name" and "last_name" columns for the author property. One thing to bear in mind with custom types is that they define the SQL types for the corresponding database columns. but here we will focus on how to map them in Grails.5) type-safe enum class: class Book { String title String author Rating rating static mapping = { rating type: RatingUserType } } All we have done is declare the rating field the enum type and set the property's type in the custom mapping to the corresponding UserType implementation. index: "my_idx". If you want. Fortunately. In such cases you need to explicitly define in the mapping what columns to use. These are not domain classes themselves. you need to override column's SQL type using the sqlType attribute: 83 . Custom types aren't limited to just a single column .You saw in an earlier section that you can use composition (via the embedded property) to break a table into multiple objects. since Hibernate can only use the property name for a single column.UserType. That's all you have to do to start using your custom type. but plain Java or Groovy classes with associated. The Hibernate reference manual has some information on custom types. cache. cascade. You'll be pleased to know that you can also use some of the normal column/property mapping attributes in the column definitions. Each of these types also has a corresponding "meta-type" class that implements org. you can also use the other column settings such as "column" to change the column name and "index" to add it to an index. lazy. Grails allows you to map multiple columns to a property using this syntax: class Book { String title Name author Rating rating static mapping = { name type: NameUserType. For example: column name: "first_name".they can be mapped to as many columns as you want. That helps take the burden of configuring them yourself.hibernate.usertype. and joinTable.
Consider a Product class like this: class Product { Float price Float taxRate Float tax } If the tax property is derived based on the value of price and taxRate properties then there may be no need to persist the tax property in the database. often but not necessarily based on the value of some other persistent property. the SQL that is generated to support that will look something like this: select product0_.5. the SQL type you specify needs to still work with the custom type. sqlType: "text" column name: "last_name". sqlType: "text" } } Mind you. which is why the example refers to PRICE and TAX_RATE instead of price and taxRate.2. when a Product is retrieved with something like Product.tax_rate as tax4_1_0_. The SQL used to derive the value of a derived property may be expressed in the ORM DSL like this: class Product { Float price Float taxRate Float tax static mapping = { tax formula: 'PRICE * TAX_RATE' } } Note that the formula expressed in the ORM DSL is SQL so references to other properties should relate to the persistence model not the object model.id=? Since the tax property is being derived at runtime and not stored in the database it might seem that the same effect could be achieved by adding a method like getTax() to the Product class that simply returns the product of the 84 . So overriding a default of "varchar" with "text" is fine. 5. With that in place. product0_.price as price1_0_. but overriding "text" with "yes_no" isn't going to work. product0_. { column name: "first_name".11 Derived Properties A derived property is a property that takes its value from a SQL expression. product0_. sqlType: "text" } rating type: RatingUserType.PRICE * product0_.class Book { String title Name author Rating rating static mapping = { name type: NameUserType.get(42).version as version1_0_.id as id1_0_.TAX_RATE as formula1_0_ from product product0_ where product0_. product0_.
PRICE * this_.tax_rate as tax4_1_0_. If constraints are specified for a derived property. With an approach like that you would give up the ability query the database based on the value of the tax property. for example one that prefixes table names and column names: 85 .findAllByTaxGreaterThan(21.groovy in the hibernate section.12) Derived properties may be referenced in the Criteria API: Product. Configure the class name to be used in grails-app/conf/DataSource.withCriteria { gt 'tax'.use_second_level_cache = true … naming_strategy = com.CustomNamingStrategy } You can use an existing class or write your own. this_. e.2. derived properties may not have GORM constraints applied to them. To retrieve all Product objects that have a tax value greater than 21. this_.id as id1_0_. this_. this_. Using a derived property allows exactly that.5.g.12f } The SQL that is generated to support either of those would look something like this: select this_.12 you could execute a query like this: Product. You can customize these on a per-instance basis in the mapping closure but if there's a consistent pattern you can specify a different NamingStrategy class to use.TAX_RATE>? Note that because the value of a derived property is generated in the database and depends on the execution of SQL code.PRICE * this_.taxRate and price properties.12 Custom Naming Strategy By default Grails uses Hibernate's ImprovedNamingStrategy to convert domain class Class and field names to SQL table and column names by converting from camel-cased Strings to ones that use underscores as word separators. 5. 21.version as version1_0_.myproj.price as price1_0_.TAX_RATE as formula1_0_ from product this_ where this_. they will be ignored.myco. dataSource { pooled = true dbCreate = "create-drop" … } hibernate { cache.
cfg.myco.ImprovedNamingStrategy import org. However.list(sort:'name') However.5.hibernate. GORM classes have been enhanced to make this more trivial through the withTransaction method which accepts a block the first argument to which is the Spring TransactionStatus object.unqualify(propertyName) } } 5.6 Programmatic Transactions Grails is built on Spring and hence uses Spring's Transaction abstraction for dealing with programmatic transactions.hibernate.StringHelper class CustomNamingStrategy extends ImprovedNamingStrategy { String classToTableName(String className) { "table_" + StringHelper.util.3 Default Sort Order You can sort objects using queries arguments such as those found in the list method: def airports = Airport.myproj import org.package com. A typical usage scenario is as follows: 86 .unqualify(className) } String propertyToColumnName(String propertyName) { "col_" + StringHelper. you can also declare the sort order declaratively: class Airport { … static mapping = { sort "name" } } You can also configure the sort order if necessary: class Airport { … static mapping = { sort name:"desc" } } Alternatively. you can configure sort order at the association level: class Airport { … static hasMany = [flights:Flight] static mapping = { flights sort:'number' } } 5.
toInteger() if(source. Grails would define these columns as.get(params. 5. String name String description By default. we'd likely define the column as follows if we were creating the table via an SQL script. it is important to mention them here as some of the constraints can affect the way in which the database schema is generated. in MySQL.amount.def transferFunds = { Account. Where feasible..active) { source.active) { dest.from) def dest = Account.setRollbackOnly() } } } } In this example we rollback the transactions if the destination account is not active and if any exception are thrown during the process the transaction will automatically be rolled back. In Grails.withTransaction { status -> def source = Account.7 GORM and Constraints Although constraints are covered in the Validation section. column name | data type description | varchar(255) But perhaps the business rules for this domain class state that a description can be up to 1000 characters in length.to) def amount = params. column name | data type description | TEXT Chances are we'd also want to have some application-based validation to make sure we don't exceed that 1000 character limit before we persist any records. This can be achieved through the use of Spring's SavePointManager interface. If that were the case. 87 . we achieve this validation via constraints.. Below is a description of the other constraints that influence schema generation. Grails uses a domain class's constraints to influence the database columns generated for the corresponding domain class properties. We'd add the following constraint declaration to the domain class.amount += amount } else { status.get(params. You can also use "save points" to rollback a transaction to a particular point in time if you don't want to rollback the entire transaction.balance -= amount if(dest. Suppose we have a domain model with the following property. Consider the following example. The withTransaction method deals with the begin/commit/rollback logic for you within the scope of the block. static constraints = { description(maxSize:1000) } This constraint would provide both the application-based validation we want and it would also cause the schema to be generated as shown above.
scale:3) would yield: someFloatValue DECIMAL(19. 5) // precision = digits in max + scale and 88 .lang. or subclasses of java.. (Grails uses the minimum of the two. for example). because any length that exceeds that minimum will result in a validation error. given a list including values "Java".. then Grails sets the column length to the minimum of the maxSize constraint and the upper bound of the size constraint. (The success of this attempted influence is largely dependent on how Hibernate interacts with the underlying DBMS.) The constraints define the minimum/maximum numeric values. then Grails uses the minimum precision value from the constraints.lang. because any length that exceeds that minimum precision will result in a validation error. the number of characters in the string "Groovy"). and "C++". unless specified constraint value requires more digits than default Hibernate column precision is (19 at the moment).Lang. However. someFloatValue(max:1000000. 3) // precision is default but someFloatValue(max:12345678901234567890.BigDecimal. In general.lang. java.Double. and Grails derives the maximum number of digits for use in the precision.) scale If the scale constraint is defined. or the range constraint is defined. (Grails uses the minimum of the two.) If the inList constraint is defined (and the maxSize and the size constraints are not defined). java.. "Groovy". Grails sets the maximum column length based on the constraint value. This rule only applies to floating point numbers (i. However. it's not advisable to use both constraints on the same domain class property.. (The success of this attempted influence is largely dependent on how Hibernate interacts with the underlying DBMS.BigDecimal). scale:5) would yield: someFloatValue DECIMAL(25. then Grails sets the maximum column length based on the length of the longest string in the list of valid values. if both of these constraints is defined. the min constraint. then Grails attempts to set the column scale based on the constraint value. Constraints Affecting Numeric Properties min max range If the max constraint. if both the maxSize constraint and the size constraint are defined. Grails attempts to set the column precision based on the constraint value. For example.e. it's not advisable to combine the pair min/max and range constraints together on the same domain class property.e.Float.) In general.Constraints Affecting String Properties inList maxSize size If either the maxSize or the size constraint is defined. java. Keep in mind that specifying only one of min/max constraints will not affect schema generation (since there could be large negative value of property with max:100. For example. Grails would set the column length to 6 (i.
2) // precision = digits in min + default scale 89 .someFloatValue(max:100. min:-100000) would yield: someFloatValue DECIMAL(8.
Each of these properties maps to a URI: class BookController { def list = { // do controller logic // create model return model } } This example maps to the /book/list URI by default thanks to the property being named list. To create a controller simply create a class whose name ends with Controller and place it within the grails-app/controllers directory. In other words a new instance is created for each request.1 Controllers A controller handles requests and creates or prepares the response and is request-scoped. The default URI is dictated by the following rules: If only one action is present the default URI for a controller maps to that action.6. For example try running the following command from the root of a Grails project: grails create-controller book The command will result in the creation of a controller at the location grails-app/controllers/BookController. The Web Layer 6. 6.1. If you define an index action which is the action that handles requests when no action is specified in the URI /book Alternatively you can set it explicitly with the defaultAction property: 90 . The Default Action A controller has the concept of a default URI that maps to the root URI of the controller. A controller can generate the response or delegate to a view.groovy: class BookController { … } BookController by default maps to the /book URI (relative to your application root). By default the default URI in this case is /book. The default URL Mapping setup ensures that the first part of your controller name is mapped to a URI and each action defined within your controller maps to URI within the controller name URI. The create-controller command is merely for convenience and you can just as easily create controllers using your favorite text editor or IDE Creating Actions A controller can have multiple properties that are each assigned a block of code.1 Understanding Controllers and Actions Creating a controller Controllers can be created with the create-controller target.
id}" redirect(action:list) } … // remaining code } 6.ServletContext session .The session allows associating state with a given user and typically uses cookies to associate a session with a client.foo def loggedUser = session.2 Controllers and Scopes Available Scopes Scopes are essentially hash like objects that allow you to store variables. Using Flash Scope Grails supports the concept of flash scope is a temporary store for attributes which need to be available for this request and the next request only.See below. Accessing Scopes Scopes can be accessed using the variable names above in combination with Groovy's array index operator even on classes provided by the Servlet API such as the HttpServletRequest: class BookController { def find = { def findBy = params["findBy"] def appContext = request["foo"] def loggedUser = session["logged_user"] } } You can even access values within scopes using the de-reference operator making the syntax even clearer: class BookController { def find = { def findBy = params.Mutable map of incoming request (CGI) parameters flash .servlet. The session object is an instance of HttpSession request . Afterwards the attributes are cleared. This is useful for setting a message directly before redirection.get( params.logged_user } } This is one of the ways that Grails unifies access to the different scopes.static defaultAction = "list" 6. for example: def delete = { def b = Book.id ) if(!b) { flash.The request object allows the storage of objects for the current request only.3 Models and Views Returning the Model 91 . The servletContext is an instance of javax.message = "User not found for id ${params.Also known as application scope. this scope allows you to share state across the entire web application.findBy def appContext = request.1. The request object is an instance of HttpServletRequest params .1. The following scopes are available to controllers: servletContext .
perhaps your favorites // forward to the list view to show them return new ModelAndView("/book/list".get( params.list() authors = Author. The keys within that map translate to variable names accessible by the view.list() } } This is possible due to the fact that controllers are prototype scoped. Otherwise code such as the above would not be thread safe.ModelAndView def index = { def favoriteBooks = … // get some books just for the index page. Notice that Grails automatically qualifies the view location with the book folder of the grails-app/views 92 . In other words a new controller is created for each request. If you wish to render another view. model:map) } In this case Grails will attempt to render a view at the location grails-app/views/book/display.gsp. There are a couple of ways to return a model. A more advanced approach is to return an instance of the Spring ModelAndView class: import org.springframework. [ bookList : favoriteBooks ]) } Selecting the View In both of the previous two examples there was no code that specified which view to render. In the above example the books and authors properties will be available in the view.id ) ] render(view:"display". as Grails can equally be used with JSP).get( params. So how does Grails know which view to pick? The answer lies in the conventions.web.gsp (actually Grails will try to look for a JSP first.servlet.id ) ] } } Grails will automatically look for a view at the location grails-app/views/book/show.get( params. For the action: class BookController { def show = { [ book : Book. the first way is to explicitly return a map instance: def show = { [ book : Book.A model is essentially a map that the view uses when rendering. then the render method there to help: def show = { def map = [ book : Book.id ) ] } If no explicit model is returned the controller's properties will be used as the model thus allowing you to write code like this: class BookController { List books List authors def list = { books = Book.
the highly flexible render method can be used: render "Hello World!" The above code writes the text "Hello World!" to the response.gsp. To correctly output a <form> elemement. other examples include: // write some markup render { for(b in books) { div(id:b.encoding:"UTF-8") If you plan on using Groovy's MarkupBuilder to generate html for use with the render method becareful of naming clashes between html elements and Grails tags.list()) // render some text with encoding and content type render(text:"<xml>some xml</xml>". b.title) } } // render a specific view render(view:'show') // render a template for each item in a collection render(template:'book_template'.directory. Rendering a Response Sometimes its easier (typically with Ajax applications) to render snippets of text or code to the response directly from the controller. model:map) } In this case Grails will attempt to render a view at the location grails-app/views/shared/display.xml. This is convenient.contentType:"text/xml". but if you have some shared views you need to access instead use: def show = { def map = [ book : Book. def login = { StringWriter w = new StringWriter() def builder = new groovy.id ) ] render(view:"/shared/display". e.id.g. use the following: 93 . For this.toString() render html } Will actually call the form tag (which will return some text that will be ignored by the MarkupBuilder).get( params.html{ head{ title 'Log in' } body{ h1 'Hello' form{ } } } def html = w. collection:Book.MarkupBuilder(w) builder.
user) redirect(action:login) … } } Internally the redirect method uses the HttpServletResonse object's sendRedirect method.org") Parameters can be optionally passed from one action to the next using the params argument of the method: redirect(action:myaction.def login = { // … body{ h1 'Hello' builder. The redirect method expects either: Another closure within the same controller class: // Call the login action within the same class redirect(action:login) The name of a controller and action: // Also redirects to the index action in the home controller redirect(controller:'home'. params:[myparam:"myvalue"]) 94 .action:'index') A URI for a resource relative the application context path: // Redirect to an explicit URI redirect(uri:"/login.form{ } } // … } 6.1.html") Or a full URL: // Redirect to a URL redirect(url:"http://grails.4 Redirects and Chaining Redirects Actions can be redirected using the redirect method present in all controllers: class OverviewController { def login = {} def find = { if(!session.
two:2. three:3] The model can be accessed in subsequent controller actions in the chain via the chainModel map. There are currently 2 types of interceptors: before and after. params:params) Finally. For example calling the first action in the below action: class ExampleChainController { def first = { chain(action:second.1. params:[myparam:"param1"]) 6. session or application state. fragment: "profile") will (depending on the URL mappings) redirect to something like "/myapp/test/show#profile".5 Controller Interceptors Often it is useful to intercept processing based on either request.model:[two:2]) } def third = { [three:3]) } } Results in the model: [one:1.These parameters are made available through the params dynamic property that also accesses request parameters. If a parameter is specified with the same name as a request parameter the request parameter is overridden and the controller parameter used. Chaining allows the model to be retained from one action to the next. model:[one:1].model:[one:1]) } def second = { chain(action:third. you can also include a fragment in the target URI: redirect(controller: "test". 95 .myModel … } } Like the redirect method you can also pass parameters to the chain method: chain(action:"action1". action: "show". This can be achieved via action interceptors. Since the params object is also a map. This dynamic property only exists in actions following the call to the chain method: class ChainController { def nextInChain = { def model = chainModel. Chaining Actions can also be chained. you can use it to pass the current request parameters from one action to the next: redirect(action:"next".
An after interceptor may also modify the Spring MVC ModelAndView object prior to rendering. A method is used so that it is not exposed as an action to the outside world (i.user) { redirect(action:'login') return false } } def login = { // display login page } The above code defines a method called auth. within the method itself it detects whether there is a user in the session otherwise it redirects to the login action and returns false.viewName = "/mycontroller/someotherview" println "View is now ${modelAndView. Interception Conditions 96 . A common use case is however for authentication: def beforeInterceptor = [action:this. The 'auth' method is referenced using Groovy's method pointer syntax.except:'login'] // defined as a regular method so its private def auth() { if(!session. Filters can be applied to multiple controllers or URIs. The beforeInterceptor then defines an interceptor that is used on all actions 'except' the login action and is told to execute the 'auth' method. without the need to change the logic of each controller Before Interception The beforeInterceptor intercepts processing before the action is executed. It will be executed before all actions and does not interfere with processing. modelAndView -> println "Current view is ${modelAndView.&auth. it is private).If your interceptor is likely to apply to more than one controller. The interceptor can be defined for all actions in a controller as follows: def beforeInterceptor = { println "Tracing action ${actionUri}" } The above is declared inside the body of the controller definition. instruction the intercepted action not to be processed. If it returns false then the intercepted action will not be executed. In this case. you are almost certainly better off writing a Filter.viewName}" } This allows the view to be changed based on the model returned by the current action. the above example becomes: def afterInterceptor = { model.viewName}" if(model. Note that the modelAndView may be null if the action being intercepted called redirect or render.someVar) modelAndView.e. After Interception To define an interceptor that is executed after an action use the afterInterceptor property: def afterInterceptor = { model -> println "Tracing action ${actionUri}" } The after interceptor takes the resulting model as an argument and can hence perform post manipulation of the model or response.
For example if you have an incoming request such as: 97 . A list of actions can also be defined as follows: def beforeInterceptor = [action:this. Binding Request Data to the Model There are two ways to bind request parameters onto the properties of a domain class. So if we had an incoming request like: /book/save?title=The%20Stand&author=Stephen%20King Then the title and author request parameters would automatically get set on the domain class.6 Data Binding Data binding is the act of "binding" incoming request parameters onto the properties of an object or an entire graph of objects.save() } This has exactly the same effect as using the implicit constructor.save() } The data binding happens within the code new Book(params). which are typically delivered via a form submission.'register']] The other supported condition is 'only'. Data binding should deal with all necessary type conversion since request parameters. this terminology conflicts with the servlet filter terminology in Java land): def beforeInterceptor = [action:this. this executes the interceptor for only the specified actions: def beforeInterceptor = [action:this.except:['login'.only:['secure']] 6. Grails uses Spring's underlying data binding capability to perform data binding.&auth.properties = params b. By passing the params object to the domain class constructor Grails automatically recognizes that you are trying to bind from request parameters.id) b.get(params. Data binding and Single-ended Associations If you have a one-to-one or many-to-one association you can use Grails' data binding capability to update these relationships too.Rails users will be familiar with the authentication example and how the 'except' condition was used when executing the interceptor (interceptors are called 'filters' in Rails.&auth. If you need to perform data binding onto an existing instance then you can use the properties property: def save = { def b = Book.except:'login'] This executes the interceptor for all actions except the specified action. are always strings whilst the properties of a Groovy or Java object may well not be.&auth.1. The first involves using a domain classes' implicit constructor: def save = { def b = new Book(params) b.
This is not a problem if you use List based associations.title" value="Red Madder" /> 98 . However.title" value="the Shining" /> <g:textField name="books[5].list()}" size="5" multiple="yes" optionKey="id" value="${author?. if you have a scenario where you want to update the properties of the associated objects the this technique won't work. Note also that if the association you are binding to has a size of 2 and you refer to an element that is outside the size of association: <g:textField name="books[0]. For example consider the usage of <g:select> below: <g:select name="books" from="${Book.id=20 Grails will automatically detect the .title" value="the Shining" /> <g:textField name="books[2].id suffix on the request parameter and look-up the Author instance for the given id when doing data binding such as: def b = new Book(params) An association property can be set to null by passing the literal String "null". so although we're referring to books0 and books1 it is not guaranteed that the order of the association will be correct on the server side unless you apply some explicit sorting yourself. If you have a Set based association (default for a hasMany) then the simplest way to populate an association is to simply send a list of identifiers.id=null Data Binding and Many-ended Associations If you have a one-to-many or many-to-many association there are different techniques for data binding depending of the association type.title" value="the Stand" /> <g:textField name="books[1]. If you "skipped" a few elements in the middle: <g:textField name="books[0]. since a List has a defined order and an index you can refer to. This is also true of Map based associations. For example: /book/save?author.title" value="the Stand" /> <g:textField name="books[1].books}" /> This produces a select box that allows you to select multiple values.title" value="the Stand" /> <g:textField name="books[1]. Instead you have to use the subscript operator: <g:textField name="books[0]. In this case if you submit the form Grails will automatically use the identifiers from the select box to populate the books association.title" value="the Shining" /> However. This is because a Set has no concept of order./book/save?author.title" value="Red Madder" /> Then Grails will automatically create a new instance for you at the defined position. with Set based association it is critical that you render the mark-up in the same order that you plan to do the update in.
For example so you have an incoming request to: /book/save?book.list()}" value="${author?. Take this example: 99 . Grails' params object is like a multi-dimensional hash and you can index into to isolate only a subset of the parameters to bind. which is used to isolate which parameters belong to which type. Binding to a Map property works in exactly the same way except that the list index in the parameter name is replaced by the map key: <g:select name="images[cover].Then Grails will automatically create instances in between.list()}" value="${author?.images[cover]?. or book. We could do the same with an Author domain class: def a = new Author(params['author']) Data binding and type conversion errors Sometimes when performing data binding it is not possible to convert a particular String into a particular target type.id" from="${Book.id" from="${Book.name=Stephen%20King You'll notice the difference with the above request is that each parameter has a prefix such as author. For example in the above case Grails will create 4 additional instances if the association being bound had a size of 2.id}" /> Would allow individual entries in the books List to be selected separately.books[0]?.id}" /> <g:select name="books[1].books[2]?.list()}" value="${author?.title parameter to isolate only parameters below this level to bind.id" from="${Image. Data binding with Multiple domain classes It is possible to bind data to multiple domain objects from the params object. Grails will retain type conversion errors inside the errors property of a Grails domain class. You can bind existing instances of the associated type to a List using the same .list()}" value="${author?.books[0]?. For example: <g:select name="books[0].list()}" value="${book?. What you get is a type conversion error.books[1]?. Entries at particular indexes can be removed in the same way too.id}" /> <g:select name="books[2].id" from="${Book. For example: <g:select name="books[0].id" from="${Book.id}" noSelection="['n Will render a select box that will remove the association at books0 if the empty option is chosen. def b = new Book(params['book']) Notice how we use the prefix before the first dot of the book.id}" noSelec This would bind the selected image into the Map property images under a key of "cover".id syntax as you would use with a single-ended association.title=The%20Stand&author.
get(1) p.net.java. the bindData method also allows you to exclude certain parameters that you don't want updated: 100 .publisherURL=The publisher URL you specified is not a valid URL Data Binding and Security concerns When batch updating properties from request parameters you need to be careful not to allow clients to bind malicious data to domain classes that end up being persisted to the database.errors. Now say we had an incoming request such as: /book/save?publisherURL=a-bad-url In this case it is not possible to bind the string a-bad-url to the publisherURL property os a type mismatch error occurs.URL=The field {0} is not a valid URL Or a more specific one: typeMismatch.'lastName'] = params In this case only the firstName and lastName properties will be bound. You can use a generic error message handler such as: typeMismatch. You can limit what properties are bound to a given domain class using the subscript operator: def p = Person. but to arbitrary objects: def p = new Person() bindData(p. The bindData method allows the same data binding capability. Alternatively there is also the flexible bindData method.properties['firstName'. Another way to do this is instead of using domain classes as the target of data binding you could use Command Objects. You can check for these like this: def b = new Book(params) if(b. for type conversion errors you would want a message to use for the error inside the grails-app/i18n/messages. params) However.class Book { … URL publisherURL } Here we have a domain class Book that uses the Java concrete type java.rejectedValue} is not a valid URL!" } Although we have not yet covered error codes (for more information see the section on Validation).net.getFieldError('publisherURL').Book.hasErrors()) { println "The value ${b.URL to represent URLs.properties file.
For example this code would produce an error: def list = { def books = Book.list() // naming conflict here render(contentType:"text/xml") { books { for(b in results) { book(title:b.list() render(contentType:"text/xml") { books { for(b in results) { book(title:b.def p = new Person() bindData(p.7 XML and JSON Responses Using the render method to output XML Grails' supports a few different ways to produce XML and JSON responses. The first one covered is via the render method. params.1. params. The render method can be passed a block of code to do mark-up building in XML: def list = { def results = Book. [exclude:'dateOfBirth']) Or include only certain properties: def p = new Person() bindData(p.title) } } } } The reason is that there is local variable books which Groovy attempts to invoke as a method.title) } } } } The result of this code would be something like: <books> <book title="The Stand" /> <book title="The Shining" /> </books> Note that you need to be careful to avoid naming conflicts when using mark-up building. [include:['firstName'. Using the render method to output JSON The render method can also be used to output JSON: 101 .'lastName]]) 6.
converters package into your controller: import grails. Automatic XML Marshalling Grails also supports automatic marshaling of domain classes to XML via special converters.0" encoding="ISO-8859-1"?> <list> <book id="1"> <author>Stephen King</author> <title>The Stand</title> </book> <book id="2"> <author>Stephen King</author> <title>The Shining</title> </book> </list> An alternative to using the converters is to use the codecs feature of Grails.list().title } } } } In this case the result would be something along the lines of: [ {title:"The Stand"}. The codecs feature provides encodeAsXML and encodeAsJSON methods: def xml = Book.encodeAsXML() render xml For more information on XML marshaling see the section on REST Automatic JSON Marshalling Grails also supports automatic marshaling to JSON via the same mechanism.list() as XML The resulting output would look something like the following:: <?xml version="1. {title:"The Shining"} ] Again the same dangers with naming conflicts apply to JSON building.* Now you can use the following highly readable syntax to automatically convert domain classes to XML: render Book.list() render(contentType:"text/json") { books = array { for(b in results) { book title:b. Simply substitute XML with JSON: 102 .converters. To start off with import the grails.def list = { def results = Book.
"releaseDate":new Date(1194127343161). the JSON builder is a custom implementation specific to Grails. {"id":2. 'c'] } This will produce: 103 .groovy: grails.8 More on JSONBuilder The previous section on on XML and JSON responses covered simplistic examples of rendering XML and JSON responses. "author":"Stephen King". "class":"Book".legacy.1. "title":"The Stand"}. Whilst the XML builder used by Grails is the standard XmlSlurper found in Groovy. 'b'.util.2 there deprecated grails. "class":"Book". if you want to use the newer/better JSONBuilder class then you can do so by setting the following in Config.render Book.json. 6.builder=false Rendering Simple Objects To render a simple JSON object just set properties within the context of the closure: render(contentType:"text/json") { hello = "world" } The above will produce the JSON: {"hello":"world"} Rendering JSON Arrays To render a list of objects simple assign a list: render(contentType:"text/json") { categories = ['a'.2 JSONBuilder For backwards compatibility the old JSonBuilder class is used with the render method for older applications. "author":"Stephen King". "title":"The Shining"} ] Again as an alternative you can use the encodeAsJSON to achieve the same effect.JSonBuilder class is used. JSONBuilder and Grails versions JSONBuilder behaves different depending on the version of Grails you use. This section covers the usage of the Grails 1. For version below 1.list() as JSON The resulting output would look something like the following: [ {"id":1.
3] Rendering Complex Objects Rendering complex objects can be done with closures. { b = "B" } ] } However. for example: render(contentType:"text/json") { categories = [ { a = "A" }. 'b'."c"]."information":{"pages":10}} Arrays of Complex Objects As mentioned previously you can nest complex objects within arrays using closures: render(contentType:"text/json") { categories = [ { a = "A" }. For example: render(contentType:"text/json") { categories = ['a'.{"categories":["a"."title":"Hello JSON". {"b":"B"}] } If you want to return a list as the root then you have to use the special element method: render(contentType:"text/json") { element 1 element 2 element 3 } The above code produces: [1.2."b". if you need to build them up dynamically then you may want to use the array method: 104 ."b". { b = "B" } ] } This will produce: {"categories":[ {"a":"A"} ."c"]} You can also render lists of complex objects. 'c'] title ="Hello JSON" information = { pages = 10 } } The above will produce the JSON: {"categories":["a".
title } } } Direct JSONBuilder API Access If you don't have access to the render method.transferTo( new File('/some/local/dir/myfile. 'b'.'Done'). The first way is to work with the Spring MultipartFile instance directly: def upload = { def f = request. 'c'] title ="Hello JSON" information = { pages = 10 } } // prints the JSON text println result. File Uploads through Data Binding File uploads can also be performed via data binding.message = 'file cannot be empty' render(view:'uploadForm') } } This is clearly handy for doing transfers to other destinations and manipulating the file directly as you can obtain an InputStream and so on via the MultipartFile interface.def results = Book.1.empty) { f.txt') ) response. but still want to produce JSON you can use the API directly: def builder = new JSONBuilder() def result = builder.render sw 6.9 Uploading Files Programmatic File Uploads Grails supports file uploads via Spring's MultipartHttpServletRequest interface.list() render(contentType:"text/json") { books = array { for(b in results) { book title:b. To upload a file the first step is to create a multipart form like the one below: Upload Form: <br /> <g:form action="upload" method="post" enctype="multipart/form-data"> <input type="file" name="myFile" /> <input type="submit" /> </g:form> There are then a number of ways to handle the file upload.toString() def sw = new StringWriter() result. } else { flash.getFile('myFile') if(!f.build { categories = ['a'.sendError(200. For example say you have an Image domain class as per the below example: 105 .
populate the properties of the command object with request parameters having corresponding names and the command object will be validated. controller actions may optionally specify any number of command object parameters. Declaring Command Objects Command objects are typically declared in the same source file as a controller directly below the controller class definition.class Image { byte[] myFile } Now if you create an image and pass in the params object such as the below example. minSize:6) } } As the previous example demonstrates you can supply constraints to command objects just as you can with domain classes. A command object is similar to a form bean in something like Struts and they are useful in circumstances when you want to populate a subset of the properties needed to update a domain class. minSize:6) password(blank:false. Grails will automatically bind the file's contents as a byte to the myFile property: def img = new Image(params) It is also possible to set the contents of the file as a string by changing the type of the myFile property on the image to a String type: class Image { String myFile } 6. For Example: 106 . Or where there is no domain class required for the interaction.1.10 Command Objects Grails controllers support the concept of command objects. but you need features such as data binding and validation. The parameter types must be supplied so that Grails knows what objects to create. For example: class UserController { … } class LoginCommand { String username String password static constraints = { username(blank:false. populate and validate. Before the controller action is executed Grails will automatically create an instance of the command object class. Using Command Objects To use command objects.
. This can then be checked in the view: <g:if test="${flash. obj -> obj.password) } } } In this example the command object interacts with a bean injected by name from the Spring ApplicationContext.canLogin(obj..1.invalidToken { // bad request } If you only provide the withForm method and not the chained invalidToken method then by default Grails will store the invalid token in a flash.invalidToken}"> Don't click the button twice! </g:if> The withForm tag makes use of the session and hence requires session affinity if used in a cluster.hasErrors()) { redirect(action:'loginForm') } else { // do something else } } } Command Objects and Dependency Injection Command objects can participate in dependency injection.username. To get started you need to define a token on the form tag: <g:form useToken="true" . This is useful if your command object has some custom validation logic which may need to interact with Grails services: class LoginCommand { def loginService String username String password static constraints = { username validator: { val. 107 . obj.class LoginController { def login = { LoginCommand cmd -> if(cmd.invalidToken variable and redirect the request back to the original page. 6.loginService.> Then in your controller code you can use the withForm method to handle valid and invalid requests: withForm { // good request }.11 Handling Duplicate Form Submissions Grails has built in support for handling duplicate form submissions using the "Synchronizer Token Pattern".
12 Simple Type Converters Type Conversion Methods If you prefer to avoid the overhead of Data Binding and simply want to convert incoming parameters (typically Strings) into another more appropriate type the params object has a number of convenience methods for each type: def total = params. The model is passed to the GSP view from a controller.title%> 108 . Handling Multi Parameters A common use case is dealing with multiple request parameters of the same name. A GSP typically has a "model" which is a set of variables that are used for view rendering. Mixing mark-up and code is a bad thing and most GSP pages contain no code and needn't do so. These same type conversion methods are also available on the attrs parameter of GSP tags. To avoid this problem the params object provides a list method that always returns a list: for(name in params.6. It is designed to be familiar for users of technologies such as ASP and JSP. char. but to be far more flexible and intuitive. there are also methods for boolean. In Grails GSPs live in the grails-app/views directory and are typically rendered automatically (by convention) or via the render method such as: render(view:"index") A GSP is typically a mix of mark-up and GSP tags which aid in view rendering.2 Groovy Server Pages Groovy Servers Pages (or GSP for short) is Grails' view technology. Although it is possible to have Groovy logic embedded in your GSP and doing this will be covered in this document the practice is strongly discouraged.int('total') The above example uses the int method.1. For example you could get a query string such as ?name=Bob&name=Judy.get(params. Each of these methods are null safe and safe from any parsing errors so you don't have to perform any addition checks on the parameters. In this case dealing with 1 parameter and dealing with many has different semantics since Groovy's iteration mechanics for String iterate over each character.list('name')) { println name } 6. For example consider the following controller action: def show = { [book: Book. long.id)] } This action will look-up a Book instance and create a model that contains a key called book. short and so on. This key can then be reference within the GSP view using the name book: <%=book.
The GrailsWebRequest instance 6.servlet.1 Variables and Scopes Within the <% %> brackets you can of course declare variables: <% now = new Date() %> And then re-use those variables further down the page: <%=now%> However.1.1 GSP Basics In the next view sections we'll go through the basics of GSP and what is available to you.This is my comment --%> <%="Hello GSP!" %> </body> </html> 6. First off let's cover some basic syntax that users of JSP and ASP should be familiar with.The HttpSession instance webRequest .The response writer for writing to the output stream params .The params object for retrieving request parameters request . GSP supports the usage of <% %> blocks to embed Groovy code (again this is discouraged): <html> <body> <% out << "Hello GSP!" %> </body> </html> As well as this syntax you can also use the <%= %> syntax to output values: <html> <body> <%="Hello GSP!" %> </body> </html> GSP also supports JSP-style server-side comments as the following example demonstrates: <html> <body> <%-.2.2 Logic and Iteration 109 .The GrailsApplication instance out .2.6.The HttpServletResponse instance session .1. within the scope of a GSP there are a number of pre-defined variables including: application .The HttpServletRequest instance response .The flash object grailsApplication .2.ServletContext instance applicationContext The Spring ApplicationContext instance flash .The javax.
unlike JSP EL you can have any Groovy expression within the ${.} parenthesis. it is rarely needed due to Groovy's default imports and GSP Tags: <%@ page import="java.awt.*" %> GSP also supports the contentType directive: <%@ page contentType="text/json" %> The contentType directive allows using GSP to render other formats.1.} are not escaped by default. you can enable automatic HTML escaping via the grails. It is present mainly to allow ASP and JSP developers to feel at home using GSP.3 Page Directives GSP also supports a few JSP-style page directives.. A GSP expression is similar to a JSP EL expression or a Groovy GString and takes the form ${expr}: <html> <body> Hello ${params.2.views.2.default. The import directive allows you to import classes into the page. so any HTML in the variable's string is output directly to the page. 6.1.each { num -> %> <p><%="Hello ${num}!" %></p> <%}%> </body> </html> As well as logical branching: <html> <body> <% if(params.3.name} </body> </html> However.4].2.Using the <% %> syntax you can of course embed loops and so on using this syntax: <html> <body> <% [1. To reduce the risk of Cross-site-scripting (XSS) attacks.default. Variables within the ${.codec setting in grails-app/conf/Config.views.4 Expressions In GSP the <%= %> syntax introduced earlier is rarely used due to the support for GSP expressions.codec='html' 110 . However..groovy: grails.hello == 'true' )%> <%="Hello!"%> <% else %> <%="Goodbye!"%> </body> </html> 6.
2. two:2. The section on Tag Libraries covers how to add your own custom tag libraries. the next sections look at the tags that are built into Grails by default. if an expression is not used it will be assumed to be a String value: <g:example attr="${new Date()}"> Hello world </g:example> Maps can also be passed into GSP tag attributes. the following sections cover GSP's built-in tags. An example GSP tag would look like: <g:example /> GSP tags can also have a body such as: <g:example> Hello world </g:example> Expressions can be passed into GSP tag attributes.2. Unlike JSP. 6.2. which are the favored way to define GSP pages. two:'two']"> Hello world </g:example> With the basic syntax out the way. which are often used for a named parameter style syntax: <g:example attr="${new Date()}" attr2="[one:1. 6.Other possible values are 'none' (for no default encoding) and 'base64'. If a tag starts with g: it is automatically assumed to be a GSP tag. You can also use the body of the <g:set> tag to define a variable: 111 . you don't need to specify any tag library imports.1 Variables and Scopes Variables can be defined within a GSP using the set tag: <g:set var="now" value="${new Date()}" /> Here we assign a variable called now to the result of a GSP expression (which simply constructs a new java. All built-in GSP tags start with the prefix g:.Date instance).2 GSP Tags Now that the less attractive JSP heritage has been set aside.util. three:3]"> Hello world </g:example> Note that within the values of attributes you must use single quotes for Strings: <g:example attr="${new Date()}" attr2="[one:'one'.
show basic functions --%> </g:else> For iteration GSP has the each and while tags: <g:each in="${[1.title}</p> </g:grep> 112 .<g:set var="myHTML"> Some re-usable code on: ${new Date()} </g:set> Variables can also be placed in one of the following scopes: page .Scoped for the user session application .2. Speaking of filters the grep tag does a similar job such as filter by class: <g:grep in="${books}" filter="NonFictionBooks.2 Logic and Iteration GSP also supports logical and iterative tags out of the box.3 Search and Filtering If you have collections of objects you often need to sort and filter them in some way.2.2.Placed within flash scope and hence available for the next request session .2. To select which scope a variable is placed into use the scope attribute: <g:set var="now" value="${new Date()}" scope="request" /> 6.3]}" var="num"> <p>Number ${num}</p> </g:each> <g:set var="num" value="${1}" /> <g:while test="${num < 5 }"> <p>Number ${num++}</p> </g:while> 6. For logic there are if.Application-wide scope. GSP supports the findAll and grep for this task: Stephen King's Books: <g:findAll in="${books}" expr="it.role == 'admin'}"> <%-.Scoped to the current request flash .title}</p> </g:findAll> The expr attribute contains a Groovy expression that can be used as a filter. else and elseif which support your typical branching scenarios: <g:if test="${session.class"> <p>Title: ${it.author == 'Stephen King'"> <p>Title: ${it.2.show administrative functions --%> </g:if> <g:else> <%-.Scoped to the current page (default) request .
.</g:form> In this case we create a form called myForm that submits to the BookController's list action.id}">${currentBook.For input fields of type 'text' checkBox .*?Groovy. currencySelect and timeZoneSelect (for selecting locale's. The form tag is a controller/action aware version of the regular HTML form tag..title. Groovy will auto-magically go through the list of Book instances.title}" filter="~/.Or using a regular expression: <g:grep in="${books.4 Links and Resources GSP also features tags to help you manage linking to controllers and actions. Multiple Submit Buttons The age old problem of dealing with multiple submit buttons is also handled elegantly with Grails via the actionSubmit tag. the most basic of which is the form tag.2.2.For input fields of type 'checkbox' radio . localeSelect. GPath is Groovy's equivalent to an XPath like language.controller:'book']">Book List</g:link> <g:link action="list" params="[sort:'title'.For input fields of type 'hidden' select .5 Forms and Fields Form Basics GSP supports many different tags for aiding in dealing with HTML forms and fields.name}</g:link> <g:link controller="book">Book Home</g:link> <g:link controller="book" action="list">Book List</g:link> <g:link url="[action:'list'.action:'list']">.author]"> Book List </g:link> 6. you can obtain a list of Book titles using the expression books. and return a new list! 6. Beyond that all of the usual HTML attributes apply. It is just like a regular submit. obtain each title.order:'asc'. but allows you to specify an alternative action to submit to: 113 .For input fields of type 'radio' hiddenField .author:currentBook.2.*?/"> <p>Title: ${it}</p> </g:grep> The above example is also interesting due to its usage of GPath. The url attribute allows you to specify which controller and action to map to: <g:form name="myForm" url="[controller:'book'.2.For dealing with HTML select boxes Each of these allow GSP expressions as the value: <g:textField name="myField" value="${myValue}" /> GSP also contains extended helper versions of the above tags such as radioGroup (for creating groups of radio tags). Form Fields As well as easy construction of forms GSP supports custom tags for dealing with different types of fields including: textField . Essentially the books collection is a collection of Book instances. even if you change them! Some examples of the link can be seen below: <g:link action="show" id="1">Book 1</g:link> <g:link action="show" id="${currentBook. However assuming each Book has a title. The link tag allows you to specify controller and action name pairing and it will automatically work out the link based on the URL Mappings. currencies and time zone's respectively).
editor() 6.jpg") If you have a custom namespace you can use that prefix instead (Example using the FCK Editor plugin): def editor = fck.jpg")} This is particularly useful when you need to use a tag within an attribute: <img src="${createLinkTo(dir:'images'. Grails has the concept of templates.6 Tags as Method Calls One major different between GSP tags and other tagging technologies is that GSP tags can be called as either regular tags or as method calls from either controllers. file:"logo. file:"logo. file:"logo. Templates are useful for separating out your views into maintainable chunks and combined with Layouts provide a highly re-usable mechanism for structure views.gsp: 114 .jpg" />" /> Tags as method calls from Controllers and Tag Libraries You can also invoke tags from controllers and tag libraries.<g:actionSubmit value="Some update label" action="update" /> 6. Tags within the default g: namespace can be invoked without the prefix and a String result is returned: def imageLocation = createLinkTo(dir:"images". you can also prefix the namespace to avoid naming conflicts: def imageLocation = g.jpg')}" /> In view technologies that don't support this feature you have to nest tags within tags. Template Basics Grails uses the convention of placing an underscore before the name of a view to identify it as a template.2.3 Views and Templates As well as views.2. tag libraries or GSP views. So for example the createLinkTo tag can equally be called as a method: Static Resource: ${createLinkTo(dir:"images".jpg") However. Tags as method calls from GSPs When called as methods tags return their results as a String instead of writing directly to the response. which becomes messy quickly and often has an adverse effect of WYSWIG tools such as Dreamweaver that attempt to render the mark-up as it is not well-formed: <img src="<g:createLinkTo dir="images" file="logo.2. file:'logo. For example a you may have a template that deals with rendering Books located at grails-app/views/book/_bookTemplate.createLinkTo(dir:"images".
gsp. you could reference it as follows: <g:render template="/shared/mySharedTemplate" /> You can also use this technique to reference templates in any directory from any view or controller: <g:render template="/book/bookTemplate" model="[book:myBook]" /> The Template Namespace Since templates are used so frequently there is template namespace. you may want to share templates across your application. which is useful for Ajax applications: 115 . available that makes using templates easier.title}</div> <div>Author: ${book?.name}</div> </div> To render this template from one of the views in grails-app/views/book you can use the render tag: <g:render template="bookTemplate" model="[book:myBook]" /> Notice how we pass into a model to use using the model attribute of the render tag. Consider for example the following usage pattern: <g:render template="bookTemplate" model="[book:myBook]" /> This can be expressed with the tmpl namespace as follows: <tmpl:bookTemplate book="${myBook}" /> Templates in Controllers and Tag Libraries You can also render templates from controllers using the render method found within controllers. In this case you can place them in the root views directory at grails-app/views or any subdirectory below that location and then with the template attribute use a / before the template name to indicate the relative template path. called tmpl. If you have multiple Book instances you can also render the template for each Book using the render tag: <g:render template="bookTemplate" var="book" collection="${bookList}" /> Shared Templates In the previous example we had a template that was specific to the BookController and its views at grails-app/views/book.author?.<div class="book" id="${book?.id}"> <div>Title: ${book?. For example if you had a template called grails-app/views/shared/_mySharedTemplate. However.
layoutTitle and layoutBody tag usages.get(params.outputs the target pages body tag contents The previous example also demonstrates the pageProperty tag which can be used to inspect and return aspects of the target page.onload')}"> <div class="menu"><!--my common menu goes here--></menu> <div class="body"> <g:layoutBody /> </div> </div> </body> </html> The key elements are the layoutHead. A typical layout can be seen below: <html> <head> <title><g:layoutTitle default="An example decorator" /></title> <g:layoutHead /> </head> <body onload="${pageProperty(name:'body. The simplest is to add a meta tag to the view: <html> <head> <title>An Example Page</title> <meta name="layout" content="main"></meta> </head> <body>This is my content!</body> </html> In this case a layout called grails-app/views/layouts/main. If you need to instead obtain the result of template as a String you can use the render tag: def show = { def b = Book.get(params. namespace which tells Grails we want to use the tag as method call instead of the render method.def show = { def b = Book.2.outputs the target page's title layoutHead . which is the most common behaviour. If we were to use the layout from the previous section the output would resemble the below: 116 .4 Layouts with Sitemesh Creating Layouts Grails leverages Sitemesh. model:[book:b]) render content } Notice the usage of the g. Triggering Layouts There are a few ways to trigger a layout.id) render(template:"bookTemplate". here is what they do: layoutTitle .gsp will be used to layout the page. 6. model:[book:b]) } The render method within controllers writes directly to the response.render(template:"bookTemplate". to support view layouts. Layouts are located in the grails-app/views/layouts directory.id) String content = g. a decorator engine.outputs the target pages head tag contents layoutBody .
gsp which will only be applied to the list action within the BookController. if you have a controller such as: class BookController { static layout = 'customer' def list = { … } } You can create a layout called grails-app/views/layouts/customer. Alternatively. which will be applied to all views that the BookController delegates to. The name of the application default layout may be changed by defining a property in grails-app/conf/Config.default.<html> <head> <title>An Example Page</title> </head> <body onload=""> <div class="menu"><!--my common menu goes here--></div> <div class="body"> This is my content! </div> </body> </html> Specifying A Layout In A Controller Another way to specify a layout is to specify the name of the layout by assigning a value to the "layout" property in a controller.layout='myLayoutName' With that property in place.gsp.gsp. The value of the "layout" property may contain a directory structure relative to the grails-app/views/layouts/ directory. For example.gsp template. For example: class BookController { static layout = 'custom/customer' def list = { … } } Views rendered from that controller would be decorated with the grails-app/views/layouts/custom/customer. the convention of last resort is to look for the application default layout which is grails-app/views/layouts/application. by convention. Layout by Convention Another way to associate layouts is to use "layout by convention".gsp which will be applied to all views that the BookController delegates to.gsp. If a layout may not be located using any of those conventions. If you have both the above mentioned layouts in place the layout specific to the action will take precedence when the list action is executed. the application default layout will be grails-app/views/layouts/myLayoutName.groovy grails.groovy as follows: // grails-app/conf/Config. if you have a controller such as: class BookController { def list = { … } } You can create a layout called grails-app/views/layouts/book.sitemesh. 117 . For example. you can create a layout called grails-app/views/layouts/book/list.
The applyLayout tag can be used to apply a layout to a template.google.com" /> <g:applyLayout name="myLayout"> The content to apply a layout to </g:applyLayout> Server-Side Includes While the applyLayout tag is useful for applying layouts to external content. you can also call the include tag from a controller or tag library as a method: def content = include(controller:"book".5 Sitemesh Content Blocks Although it is useful to decorate an entire page sometimes you may find the need to decorate independent sections of your site. To get started you need to divide the page to be decorate using the <content> tag: <content tag="navbar"> … draw the navbar here… </content> <content tag="header"> … draw the header here… </content> <content tag="footer"> … draw the footer here… </content> <content tag="body"> … draw the body here… </content> Then within the layout you can reference these components and apply individual layouts to each: 118 . To do this you can use content blocks. URL or arbitrary section of content.Inline Layouts Grails' also supports Sitemesh's concept of inline layouts with the applyLayout tag. 6. Essentially. if you simply want to include external content in the current page you can do so with the include: <g:include controller="book" action="list"></g:include> You can even combine the include tag and the applyLayout tag for added flexibility: <g:applyLayout name="myLayout"> <g:include controller="book" action="list"></g:include> </g:applyLayout> Finally. Some examples of usage can be seen below: <g:applyLayout name="myLayout" template="bookTemplate" collection="${books}" /> <g:applyLayout name="myLayout" url="http://www. this allows to even further modularize your view structure by "decorating" your template includes. action:"list") The resulting content will be provided via the return value of the include tag.2.
this would look something like this: mkdir -p /var/www/grails/my-app/grails-app/views cp -R grails-app/views/* /var/www/grails/my-app/grails-app/views The key point here is that you must retain the view directory structure. Let's say we want to keep them unpacked in a /var/www/grails/my-app directory. it can seem like a lot of unnecessary work.gsp. If all you want to do is fix a typo on a page.dir value is important! Without it. it uses up permgen space. The second line tells Grails where to load the views and layouts from.gsp. The trailing slash on the grails. If you don't have this setting.3 Tag Libraries Like Java Server Pages (JSP).6 Making Changes to a Deployed Application One of the main issues with deploying a Grails application (or typically any servlet-based one) is that any change to the views requires you to redeploy your whole application. On a Unix-like system. or change an image link.gsp. elegant and completely reload-able at runtime. So you end up with the path /var/www/grails/my-app/grails-app/views/. Quite simply.navbar"> </g:applyLayout> </div> <div id="body"> <g:applyLayout name="bodyLayout"> <g:pageProperty name="page. Grails will look for views in the parent directory. Grails does have a solution: the grails.gsp.footer"> </g:applyLayout> </div> </body> </html> 6. One thing to bear in mind with this technique is that every time you modify a GSP.enable.dir = "/var/www/grails/my-app/" The first line tells Grails that modified GSP files should be reloaded at runtime. GSP supports the concept of custom tag libraries. So at some point you will eventually hit "out of permgen space" errors unless you restart the server. to create a tag library create a Groovy class that ends with the convention TagLib and place it within 119 .view.groovy : grails.. So this technique is not recommended for frequent or large changes to the views. With those settings in place. including the grails-app/views bit. 6.2. How does this work? The first step is to decide where the GSP files should go.view. Grails tag library mechanism is simply. you can make as many changes as you like but they won't be reflected in the running application.dir configuration setting. For such simple requirements..view.reload = true grails. We add these two lines to grails-app/conf/Config. Unlike JSP. all you need to do is copy the views from your web application to the external directory.body"> </g:applyLayout> </div> <div id="footer"> <g:applyLayout name="footerLayout"> <g:pageProperty name="page.header"> </g:applyLayout> </div> <div id="nav"> <g:applyLayout name="navLayout"> <g:pageProperty name="page. .<html> <body> <div id="header"> <g:applyLayout name="headerLayout"> <g:pageProperty name="page.
The response writer for writing to the output stream pageScope .3.3.A reference to the pageScope object used for GSP rendering (i.e.The currently executing controller name flash .format(attrs.text.The GrailsApplication instance out .The HttpSession instance 6. whilst the body argument is another invokable block of code that returns the body content: class SimpleTagLib { def emoticon = { attrs.The javax. body -> out << body() << (attrs.the grails-app/taglib directory: class SimpleTagLib { } Now to create a tag simply create property that is assigned a block of code that takes two arguments: The tag attributes and the body content: class SimpleTagLib { def simple = { attrs.happy == 'true' ? " :-)" : " :-(") } } As demonstrated above there is an implicit out variable that refers to the output Writer which you can use to append content to the response.2 Simple Tags As demonstrated it the previous example it is trivial to write simple tags that have no body and merely output content. body -> } } The attrs argument is a simple map of the attributes of the tag. no imports necessary: <g:emoticon happy="true">Hi John</g:emoticon> 6.The context path to the plugin that contains the tag library request .The params object for retrieving request parameters pluginContextPath .The currently executing action name controllerName .The HttpServletResponse instance servletContext . the binding) params .ServletContext instance session .The HttpServletRequest instance response . Then you can simply reference the tag inside your GSP.The flash object grailsApplication . The tag can 120 .SimpleDateFormat(attrs.format).servlet. Another example is a dateFormat style tag: def dateFormat = { attrs.1 Variables and Scopes Within the scope of a tag library there are a number of pre-defined variables including: actionName . body -> out << new java.date) } The above uses Java's SimpleDateFormat class to format a date and then write it to the response.
book.3 Logical Tags You can also create logical tags where the body of the tag is only output once a set of conditions have been met.3. A better approach would be to re-use the render tag: def formatBook = { attrs.then be used within a GSP as follows: <g:dateFormat format="dd-MM-yyyy" date="${new Date()}" /> With simple tags sometimes you need to write HTML mark-up to the response. body -> def user = attrs['user'] if(user != null && checkUserPrivs(user)) { out << body() } } The tag above checks if the user is an administrator and only outputs the body content if he/she has the correct set of access privileges: <g:isAdmin user="${myUser}"> // some restricted content </g:isAdmin> 6. body -> out << "<div id="${attrs.3. An example of this may be a set of security tags: def isAdmin = { attrs. One approach would be to embed the content directly: def formatBook = { attrs. model:[book:attrs. 6. since you can invoke the body multiple times: def repeat = { attrs.4 Iterative Tags Iterative tags are trivial too.id}">" out << "Title : ${attrs.book.times?. body -> out << render(template:"bookTemplate".times { num -> out << body(num) } } In this example we check for a times attribute and if it exists convert it to a number then use Groovy's times method to iterate by the number of times specified by the number: 121 .toInteger().title}" out << "</div>" } Although this approach may be tempting it is not very clean. body -> attrs.book]) } And then have a separate GSP template that does the actual rendering.
However. This works because when we invoked the body we passed in the current value inside the iteration: out << body(num) That value is then passed as the default variable it to the tag. Now we can change the usage of the tag as follows: <g:repeat times="3" var="j"> <p>Repeat this 3 times! Current repeat = ${j}</p> </g:repeat> Notice how we use the var attribute to define the name of the variable j and then we are able to reference that variable within the body of the tag.<g:repeat times="3"> <p>Repeat this 3 times! Current repeat = ${it}</p> </g:repeat> Notice how in this example we use the implicit it variable to refer to the current number.var ? attrs.toInteger().times?.times { num -> out << body((var):num) } } Here we check if there is a var attribute and if there is use that as the name to pass into the body invocation on this line: out << body((var):num) Note the usage of the parenthesis around the variable name. 6.3. you can specify a different namespace by adding a static property to your TagLib class: class SimpleTagLib { static namespace = "my" def example = { attrs -> … } } Here we have specified a namespace of my and hence the tags in this tag lib must then be referenced from GSP pages like this: 122 . However. body -> def var = attrs. if you have nested tags this can lead to conflicts.5 Tag Namespaces By default.var : "num" attrs. If you omit these Groovy assumes you are using a String key and not referring to the variable itself. tags are added to the default Grails namespace and are used with the g: prefix in GSP pages. hence you should should instead name the variables that the body uses: def repeat = { attrs.
String instance was returned. this convention is not hard wired into Grails and is in fact controlled by a URL Mappings class located at grails-app/conf/UrlMappings.groovy. controllers or tag libraries 6.lang.2.web. a tag library call returns an instance of org.code)?. Namespaces are particularly useful for plugins.content } } 6.util.formatNumber(value:10.<my:example name="." /> Where the prefix is the same as the value of the static namespace property.2. Object returning tag names are listed in a static returnObjectForTags property in the tag library class. Example: class ObjectReturningTagLib { static namespace = "cms" static returnObjectForTags = ['content'] def content = { attrs.. a java. However.4 URL Mappings Throughout the documentation so far the convention used for URLs has been the default of /controller/action/id. This change improves performance by reducing object creation and optimizing buffering during request processing.3.sun.example(name:"foo") This works from GSP.groovy.StreamCharBuffer class by default. The UrlMappings class contains a single property called mappings that has been assigned a block of code: 123 ...findByCode(attrs.00")} 6. In earlier Grails versions.6 Using JSP Tag Libraries In addition to the simplified tag library mechanism provided by GSP.3. pattern:".com/jsp/jstl/fmt" %> Then you can use it like any other tag: <fmt:formatNumber value="${10}" pattern=". body -> CmsContent.00"/> With the added bonus that you can invoke JSP tags like methods: ${fmt.7 Tag return value Since Grails 1. you can also use JSP tags from GSP. Tag libraries can also return direct object values to the caller since Grails 1. Tags within namespaces can be invoked as methods using the namespace as a prefix to the method call: out << my.grails.codehaus. To do so simply declare the JSP you want to use via the taglib directive: <%@ taglib prefix="fmt" uri="http://java.
action:"list") In this case we've mapped the URL /product to the list action of the ProductController. In this case you can use variable placeholders within the URL for example: static mappings = { "/product/$id"(controller:"product") } In this case by embedding a $id variable as the second token Grails will automatically map the second token into a parameter (available via the params object) called id. If you simply want to rewrite on URI onto another explicit URI (rather than a controller/action pair) this can be achieved with the following example: "/hello"(uri:"/hello. A concrete token is one which is well defined such as as /product.2 Embedded Variables Simple Variables The previous section demonstrated how to map trivial URLs with concrete "tokens". in many circumstances you don't know what the value of a particular token will be until runtime.dispatch") Rewriting specific URIs is often useful when integrating with other frameworks. However. 6.1 Mapping to Controllers and Actions To create a simple mapping simply use a relative URL as the method name and specify named parameters for the controller and action to map to: "/product"(controller:"product".4.class UrlMappings { static mappings = { } } 6. You could of course omit the action definition to map to the default action of the controller: "/product"(controller:"product") An alternative syntax is to assign the controller and action to use within a block passed to the method: "/product" { controller = "product" action = "list" } Which syntax you use is largely dependent on personal preference. In URL mapping speak tokens are the sequence of characters between each slash / character. the following code will render "MacBook" to the response: 124 . For example given the URL /product/MacBook.4.
In fact the default Grails URL mappings use this technique: static mappings = { "/$controller/$action?/$id?"() } Here the name of the controller.class ProductController { def index = { render params. id and so on. action:"show") } With this mapping all of the below URLs would match with only the relevant parameters being populated in the params object: 125 . day. action and id embedded within the URL. You can also resolve the controller name and action name to execute dynamically using a closure: static mappings = { "/$controller" { action = { params. action and id are implicitly obtained from the variables controller. month.goHere } } } Optional Variables Another characteristic of the default mapping is the ability to append a ? at the end of a variable to make it an optional token. For example the traditional blog URL format could be mapped as follows: static mappings = { "/$blog/$year/$month/$day/$id"(controller:"blog".id } } You can of course construct more complex examples of mappings. Dynamic Controller and Action Names Variables can also be used to dynamically construct the controller and action name. In a further example this technique could be applied to the blog URL mapping to have more flexible linking: static mappings = { "/$blog/$year?/$month?/$day?/$id?"(controller:"blog". action:"show") } The above mapping would allow you to do things like: /graemerocher/2007/01/10/my_funky_blog_entry The individual tokens in the URL would again be mapped into the params object with values available for year.
4.view:"help") // to a view for a controller } 6. action: "forbidden") "404"(controller: "errors". actions or views.4. This is also possible by assigning a block to the variable name: "/holiday/win" { id = { params. action: "notFound") "500"(controller: "errors". 6. without a controller or action involved.3 Mapping to Views If you want to resolve a URL to a view.id } isEligible = { session. All you have to do is use a method name that matches the response code you are interested in: static mappings = { "403"(controller: "errors". For example if you wanted to map the root URL / to a GSP at the location grails-app/views/index. you can do so too.4 Mapping to Response Codes Grails also allows you to map HTTP response codes to controllers.gsp you could use: static mappings = { "/"(view:"/index") } // map the root URL Alternatively if you need a view that is specific to a given controller you could use: static mappings = { "/help"(controller:"site". Dynamically Resolved Variables The hard coded arbitrary variables are useful. action: "serverError") } 126 .user != null } // must be logged in } In the above case the code within the blocks is resolved when the URL is actually matched and hence can be used in combination with all sorts of logic./graemerocher/2007/01/10/my_funky_blog_entry /graemerocher/2007/01/10 /graemerocher/2007/01 /graemerocher/2007 /graemerocher Arbitrary Variables You can also pass arbitrary parameters from the URL mapping into the controller by merely setting them in the block passed to the mapping: "/holiday/win" { id = "Marrakech" year = 2007 } This variables will be available within the params object passed to the controller. but sometimes you need to calculate the name of the variable based on runtime factors.
POST:"save"] } } 6. action: "nullPointer". PUT:"update". As an example the following mappings provide a RESTful API URL mappings for the ProductController: static mappings = { "/product/$id"(controller:"product"){ action = [GET:"show". a NullPointerException will be handled by the nullPointer action.4. Other exceptions will be handled by the catch-all rule and use the /errors/serverError view. This is extremely useful for RESTful APIs and for restricting mappings based on HTTP method. you can also use double wildcards to match more than one level below: 127 .4. action: "customException". exception: MyException) "500"(view: "/errors/serverError") } With this configuration.jpg. and a MyException will be handled by the customException action. an IllegalArgumentException will be handled by the illegalArgument action in ErrorsController. exception: IllegalArgumentException) "500"(controller: "errors".jpg"(controller:"image") } However.6 Mapping Wildcards Grails' URL mappings mechanism also supports wildcard mappings. exception: NullPointerException) "500"(controller: "errors".5 Mapping to HTTP methods URL mappings can also be configured to map based on the HTTP method (GET. For example consider the following mapping: static mappings = { "/images/*. DELETE:"delete".jpg"(controller:"image") } This mapping will match all paths to images such as /image/logo. 6. Of course you can achieve the same effect with a variable: static mappings = { "/images/$name. action: "illegalArgument".Or alternatively if you merely want to provide custom error pages: static mappings = { "403"(view: "/errors/forbidden") "404"(view: "/errors/notFound") "500"(view: "/errors/serverError") } Declarative Error Handling In addition you can configure handlers for individual exceptions: static mappings = { "403"(view: "/errors/forbidden") "404"(view: "/errors/notFound") "500"(controller: "errors". PUT or DELETE). POST.
action:"show") } If you use the link tag as follows: <g:link controller="blog" action="show" params="[blog:'fred'. So given a mapping such as the blog one from an earlier section: static mappings = { "/$blog/$year?/$month?/$day?/$id?"(controller:"blog". "/css/*"] static mappings = { … } } In this case Grails won't attempt to match any URIs that start with /images or /css.groovy class: class UrlMappings = { static excludes = ["/images/*".static mappings = { "/images/**.7 Automatic Link Re-Writing Another great feature of URL mappings is that they automatically customize the behaviour of the link tag so that changing the mappings don't require you to go and change all of your links.jpg and /image/other/logo.jpg"(controller:"image") } In this case it will store the path matched by the wildcard inside a name parameter obtainable from the params object: def name = params. This is done through a URL re-writing technique that reverse engineers the links from the URL mappings.jpg as well as /image/other/logo.name println name // prints "logo" or "other/logo" If you are using wildcard URL mappings then you may want to exclude certain URIs from Grails' URL mapping process.4. To do this you can provide an excludes setting inside the UrlMappings. month:10]">My Blog .jpg "/images/$name**.jpg. year:2007]">My Blog</g:link> <g:link controller="blog" action="show" params="[blog:'fred'. year:2007.Octob Grails will automatically re-write the URL in the correct format: <a href="/fred/2007">My Blog</a> <a href="/fred/2007/10">My Blog . Even better you can use a double wildcard variable: static mappings = { // will match /image/logo.October 2007 Posts</a> 128 .jpg"(controller:"image") } In this cases the mapping will match /image/logo. 6.
action:"show") } This allows URLs such as: /graemerocher/2007/01/10/my_funky_blog_entry However. which allows you to further "constrain" how a URL is matched. 6.9 Named URL Mappings URL Mappings also support named mappings. Luckily. it would also allow: /graemerocher/not_a_year/not_a_month/not_a_day/my_funky_blog_entry This is problematic as it forces you to do some clever parsing in the controller code. the mapping currently looks like this: static mappings = { "/$blog/$year?/$month?/$day?/$id?"(controller:"blog". The syntax for defining a named mapping is as follows: static mappings = { name <mapping name>: <url pattern> { // … } } An example: 129 .6. For example. named mappings are mappings which have a name associated with them. month and day parameters match a particular valid pattern thus relieving you of that burden later on.4.8 Applying Constraints URL Mappings also support Grails' unified validation constraints mechanism. Simply put.4. if we revisit the blog sample code from earlier. The name may be used to refer to a specific mapping when links are being generated. URL Mappings can be constrained to further validate the URL tokens: "/$blog/$year?/$month?/$day?/$id?" { controller = "blog" action = "show" constraints { year(matches:/\d{4}/) month(matches:/\d{2}/) day(matches:/\d{2}/) } } In this case the constraints ensure that the year.
static mappings = { name personList: "/showPeople" { controller = 'person' action = 'list' } name accountDetails: "/details/$acctNumber" { controller = 'product' action = 'accountDetails' } }
The mapping may be referenced in a link tag in a GSP.
<g:link mapping="personList">List People</g:link>
That would result in:
<a href="/showPeople">List People</a>
Parameters may be specified using the params attribute.
<g:link mapping="accountDetails" params="[acctNumber:'8675309']">Show Account</g:link>
That would result in:
<a href="/details/8675309">Show Account</a>
Alternatively you may reference a named mapping using the link namespace.
<link:personList>List People</link:personList>
That would result in:
<a href="/showPeople">List People</a>
The link namespace approach allows parameters to be specified as attributes.
<link:accountDetails acctNumber="8675309">Show Account</link:accountDetails>
That would result in:
<a href="/details/8675309">Show Account</a>
6.5 Web Flow
Overview Grails supports the creation of web flows built on the Spring Web Flow project. A web flow is a conversation that spans multiple requests and retains state for the scope of the flow. A web flow also has a defined start and end state. Web flows don't require an HTTP session, but instead store their state in a serialized form, which is then restored using a flow execution key that Grails passes around as a request parameter. This makes flows far more scalable than other forms of stateful application that use the HttpSession and its inherit memory and clustering concerns. Web flow is essentially an advanced state machine that manages the "flow" of execution from one state to the next. Since the state is managed for you, you don't have to be concerned with ensuring that users enter an action in the middle of some multi step flow, as web flow manages that for you. This makes web flow perfect for use cases such as shopping carts, hotel booking and any application that has multi page work flows. Creating a Flow To create a flow create a regular Grails controller and then add an action that ends with the convention Flow. For example:
class BookController { def index = { redirect(action:"shoppingCart") } def shoppingCartFlow = { … } }
Notice when redirecting or referring to the flow as an action we omit the Flow suffix. In other words the name of the action of the above flow is shoppingCart.
6.5.1 Start and End States
As mentioned before a flow has a defined start and end state. A start state is the state which is entered when a user first initiates a conversation (or flow). The start state of A Grails flow is the first method call that takes a block. For example:
class BookController { … def shoppingCartFlow = { showCart { on("checkout").to "enterPersonalDetails" on("continueShopping").to "displayCatalogue" } … displayCatalogue { redirect(controller:"catalogue", action:"show") } displayInvoice() } }
Here the showCart node is the start state of the flow. Since the showCart state doesn't define an action or redirect it is assumed be a view state that, by convention, refers to the view grails-app/views/book/shoppingCart/showCart.gsp. Notice that unlike regular controller actions, the views are stored within a directory that matches the name of the flow: grails-app/views/book/shoppingCart. The shoppingCart flow also has two possible end states. The first is displayCatalogue which performs an external redirect to another controller and action, thus exiting the flow. The second is displayInvoice which is an end state as it has no events at all and will simply render a view called grails-app/views/book/shoppingCart/displayInvoice.gsp whilst ending the flow at the same time. Once a flow has ended it can only be resumed from the start state, in this case showCart, and not from any other state.
6.5.2 Action States and View States 131
View states A view state is a one that doesn't define an action or a redirect. So for example the below is a view state:
enterPersonalDetails { on("submit").to "enterShipping" on("return").to "showCart" }
It will look for a view called grails-app/views/book/shoppingCart/enterPersonalDetails.gsp by default. Note that the enterPersonalDetails state defines two events: submit and return. The view is responsible for triggering these events. If you want to change the view to be rendered you can do so with the render method:
enterPersonalDetails { render(view:"enterDetailsView") on("submit").to "enterShipping" on("return").to "showCart" }
Now it will look for grails-app/views/book/shoppingCart/enterDetailsView.gsp. If you want to use a shared view, start with a / in view argument:
enterPersonalDetails { render(view:"/shared/enterDetailsView") on("submit").to "enterShipping" on("return").to "showCart" }
Now it will look for grails-app/views/shared/enterDetailsView.gsp Action States An action state is a state that executes code but does not render any view. The result of the action is used to dictate flow transition. To create an action state you need to define an action to to be executed. This is done by calling the action method and passing it a block of code to be executed:
listBooks { action { [ bookList:Book.list() ] } on("success").to "showCatalogue" on(Exception).to "handleError" }
As you can see an action looks very similar to a controller action and in fact you can re-use controller actions if you want. If the action successfully returns with no errors the success event will be triggered. In this case since we return a map, this is regarded as the "model" and is automatically placed in flow scope. In addition, in the above example we also use an exception handler to deal with errors on the line:
on(Exception).to "handleError"
What this does is make the flow transition to a state called handleError in the case of an exception. You can write more complex actions that interact with the flow request context:
processPurchaseOrder { action { def a = flow.address def p = flow.person def pd = flow.paymentDetails def cartItems = flow.cartItems flow.clear() def o = new Order(person:p, shippingAddress:a, paymentDetails:pd) o.invoiceNumber = new Random().nextInt(9999999) cartItems.each { o.addToItems(it) } o.save() [order:o] } on("error").to "confirmPurchase" on(Exception).to "confirmPurchase" on("success").to "displayInvoice" }
Here is a more complex action that gathers all the information accumulated from the flow scope and creates an Order object. It then returns the order as the model. The important thing to note here is the interaction with the request context and "flow scope". Transition Actions Another form of action is what is known as a transition action. A transition action is executed directly prior to state transition once an event has been triggered. A trivial example of a transition action can be seen below:
enterPersonalDetails { on("submit") { log.trace "Going to enter shipping" }.to "enterShipping" on("return").to "showCart" }
Notice how we pass a block of the code to submit event that simply logs the transition. Transition states are extremely useful for data binding and validation, which is covered in a later section.
6.5.3 Flow Execution Events
In order to transition execution of a flow from one state to the next you need some way of trigger an event that indicates what the flow should do next. Events can be triggered from either view states or action states. Triggering Events from a View State As discussed previously the start state of the flow in a previous code listing deals with two possible events. A checkout event and a continueShopping event:
def shoppingCartFlow = { showCart { on("checkout").to "enterPersonalDetails" on("continueShopping").to "displayCatalogue" } … }
Since the showCart event is a view state it will render the view grails-app/book/shoppingCart/showCart.gsp. Within this view you need to have components that trigger flow execution. On a form this can be done use the submitButton tag:
<g:form action="shoppingCart"> <g:submitButton name="continueShopping" value="Continue Shopping"></g:submitButton> <g:submitButton name="checkout" value="Checkout"></g:submitButton> </g:form>
to "enterPayment" } 6. With an action state you can also trigger events to redirect flow: shippingNeeded { action { if(params.to "enterShipping" on("return").Stores objects for the scope of the flow. Also returning a model map from an action will automatically result in the model being placed in flow scope.to "showCart" } In this case because of the error the transition action will make the flow go back to the enterPersonalDetails state. removing them when the flow reaches an end state conversation . If you don't have a form you can also trigger an event with the link tag as follows: <g:link action="shoppingCart" event="checkout" /> Triggering Events from an Action To trigger an event from an action you need to invoke a method. using a transition action.5.Stores objects for the scope of the conversation including the root flow and nested subflows session .person = p if(!p.validate())return error() }.shippingRequired) yes() else no() } on("yes"). The example below triggers the error() event on validation failure in a transition action: enterPersonalDetails { on("submit") { def p = new Person(params) flow.Stores an object for the scope of the current request flash . Grails flows have 5 different scopes you can utilize: request .Stores the object for the current and next request only flow .4 Flow Scopes Scope Basics You'll notice from previous examples that we used a special object called flow to store objects within "flow scope". For example. you can place objects within flow scope as follows: enterPersonalDetails { on("submit") { [person:new Person(params)] }.to "showCart" } 134 . See the documentation on Services for more information. For example there is the built in error() and success() methods.The form must submit back to the shoppingCart flow.to "enterShipping" on("no").Stores objects inside the users session Grails service classes can be automatically scoped to a web flow scope.to "enterShipping" on("return"). The name attribute of each submitButton tag signals which event will be triggered.
flow or conversation scope they must implement java. For example consider this: class Book implements Serializable { String title Author author } Here if the Author association is not Serializable you will also get an error. This has an impact on domain classes in that domain classes are typically placed within a scope so that they can be rendered in a view. To get around this you should declare all events as transient: class Book implements Serializable { String title transient onLoad = { println "I'm loading" } } 6. 2.5 Data Binding and Validation 135 . GSP pages).Serializable otherwise you will get an error.io. The following domain class will cause an error if an instance is placed in a flow scope: class Book implements Serializable { String title def onLoad = { println "I'm loading" } } The reason is that the assigned block on the onLoad event cannot be serialized. Moves objects from flash scope to request scope upon transition between states. This also impacts closures used in GORM events such as onLoad. Merges objects from the flow and conversation scopes into the view model before rendering (so you shouldn't include a scope prefix when referencing these objects within a view. Flow Scopes and Serialization When placing objects in flash. so an object placed in request scope in an action state (for example) will not be available in a subsequent view state.5. Use one of the other scopes to pass objects from one state to another. For example consider the following domain class: class Book { String title } In order to place an instance of the Book class in a flow scope you will need to modify it as follows: class Book implements Serializable { String title } This also impacts associations and closures you declare within a domain class.g. onSave and so on. e.Be aware that a new request is always created for each state. Also note that Web Flow: 1.
5.to "showCart" } 6.to "showCart" } Notice how we perform data binding from request parameters and place the Person instance within flow scope.6 Subflows and Conversations Grails' Web Flow integration also supports subflows. Like regular actions.to "enterShipping" on("return"). Also interesting is that we perform validation and invoke the error() method if validation fails.Other fields --> <g:submitButton name="submit" value="Continue"></g:submitButton> <g:submitButton name="return" value="Back"></g:submitButton> </g:form> However. This state renders a view and waits for the user to enter the required information: enterPersonalDetails { on("submit").personDetails = cmd !flow.validate() ? error() : success() }.In the section on start and end states.person = new Person(params) !flow.person. flow actions also support the notion of Command Objects by defining the first argument of the closure: enterPersonalDetails { on("submit") { PersonDetailsCommand cmd -> flow.validate() ? error() : success() }.personDetails. the start state in the first example triggered a transition to the enterPersonalDetails state.to "enterShipping" on("return"). otherwise the transition should continue and go to the enterShipping state. what about the capturing the information submitted by the form? To to capture the form info we can use a flow transition action: enterPersonalDetails { on("submit") { flow. This signals to the flow that the transition should halt and return to the enterPersonalDetails view so valid entries can be entered by the user.to "enterShipping" on("return"). For example take this search flow: 136 . A subflow is like a flow within a flow.to "showCart" } The view contains a form with two submit buttons that either trigger the submit event or the return event: <g:form action="shoppingCart"> <!-.
conversation.q)] } on("success").1 Applying Filters To create a filter create a class that ends with the convention Filters in the grails-app/conf directory.to "displayNoMoreResults" } displayMoreResults() displayNoMoreResults() } It references a subflow in the extendedSearch state.to "searchMore" on("searchAgain").6.6 Filters Although Grails controllers support fine grained interceptors. and so on. The subflow is another flow entirely: def extendedSearchFlow = { startExtendedSearch { on("findMore").to "displaySearchForm" } extendedSearch { subflow(extendedSearchFlow) // <--. Filters are far easier to plug-in and maintain completely separately to your main controller logic and are useful for all sorts of cross cutting concerns such as security.extended search subflow on("moreResults").to "moreResults" on("error").to "extendedSearch" on("searchAgain").to "displayNoMoreResults" } 6. 6.executeSearch(params.query) if(!results)return error() conversation. logging. Within this class define a code block called filters that contains the filter definitions: 137 . This scope differs to flow scope as it allows you to share state that spans the whole conversation not just the flow.deepSearch(ctx.to "displayResults" on("error").to "displaySearchForm" } displayResults { on("searchDeeper"). Filters on the other hand can be applied across a whole group of controllers.to "displayMoreResults" on("noResults").def searchFlow = { displaySearchForm { on("submit"). Also notice that the end state (either moreResults or noResults of the subflow triggers the events in the main flow: extendedSearch { subflow(extendedSearchFlow) // <--.to "noResults" } moreResults() noResults() } Notice how it places the extendedResults in conversation scope. a URI space or a to a specific action.to "executeSearch" } executeSearch { action { [results:searchService.to "displayMoreResults" on("noResults").extended search subflow on("moreResults").to "noResults" } searchMore { action { def results = searchService. these are only really useful when applied to a few controllers and become difficult to manage with larger applications.extendedResults = results } on("success").
by default * is replaced with .action matching pattern.rule matches with partial match (see java.class ExampleFilters { def filters = { // your filters here } } Each filter you define within the filters block has a name and a scope. action:'*') { } All controllers except the BookController notBook(controller:'book'.a uri to match.g. by default * is replaced with . invert:true) { } All actions containing 'save' in the action name saveInActionName(action:'save'. find:true) { } Applied to a URI space 138 .* and a regex is compiled regex (true/false) .controller matching pattern.* and a regex is compiled action .find()) invert (true/false) .Matcher. For example if you need to define a filter that applies to all controllers and all actions you can use wildcards: sampleFilter(controller:'*'. expressed with as Ant style path (e.*') uri . /book/**) find (true/false) . with Ant path matching syntax Filter rule attributes: controller . action:'*') { } Only for the BookController justBook(controller:'book'. action:'*') { // interceptor definitions } The scope of the filter can be one of the following things: A controller and/or action name pairing with optional wildcards A URI.invert the rule (NOT rule) Some examples of filters include: All controllers and actions all(controller:'*'. The name is the method name and the scope is defined using named arguments.use regex syntax (don't replace '*' with '.regex.util.
To control the order of execution between Filters classes. filters only support a subset of the methods available to controllers and tag libraries.3 Variables and Scopes Filters support all the common properties available to controllers and tag libraries.The controller name that is being dispatched to grailsApplication . Can return false to indicate all future filters and the action should not execute after .The HttpSession object servletContext .The HttpServletRequest object response . Takes a first argument as the view model afterView .The HttpServletResponse object session .Executed before the action.6.4 Filter Dependencies In a Filters class.someURIs(uri:'/book/**') { } Applied to all URIs allURIs(uri:'/**') { } In addition.2 Filter Types Within the body of the filter you can then define one or several of the following interceptor types for the filter: before .6. the order in which you define the filters within the filters code block dictates the order in which they are executed.6.equals('login')) { redirect(action:'login') return false } } } } } Here the loginCheck filter uses a before interceptor to execute a block of code that checks if a user is in the session and if not redirects to the login action.The request parameters object actionName . 6. 6.The Grails application currently running applicationContext .The action name that is being dispatched to controllerName . plus the application context: request .The flash object params . Note how returning false ensure that the action itself is not executed. you can use the dependsOn property discussed in filter dependencies section.For redirects to other controllers and actions render .Executed after view rendering For example to fulfill the common authentication use case you could define a filter as follows: class SecurityFilters { def filters = { loginCheck(controller:'*'. action:'*') { before = { if(!session. These include: redirect . you can specify any other Filters classes that should first be executed using the 139 .The ApplicationContext object However.user && !actionName.For rendering custom responses 6.Executed after an action.The ServletContext object flash .
The javascript function to call when the remote function is complete.The javascript function to call to handle specified error codes (eg on404="alert('not found!')") onUninitialized .The javascript function to call when the remote function is completed loading the response onComplete . or take other action: <g:remoteLink action="show" id="1" update="success" onLoading="showProgress()" onComplete="hideProgress()">Show Book 1</g:remoteLink> The above code will execute the "showProgress()" function which may show a progress bar or whatever is appropriate. Other events include: onSuccess .The javascript function to call when the remote function is loading the response onLoaded .The javascript function to call if the call failed on_ERROR_CODE .<g:formRemote url="[controller:'book'.The javascript function to call the a ajax engine failed to initialise onLoading .7.1. including any updates If you need a reference to the XmlHttpRequest object you can use the implicit event parameter e to obtain it: <g:javascript> function fireMe(e) { alert("XmlHttpRequest = " + e) } } </g:javascript> <g:remoteLink action="example" update="success" onSuccess="fireMe(e)">Ajax Link</g:remoteLink> 6. This allows some buttons to submit remotely and some not depending on the action: <form action="delete"> <input type="hidden" name="id" value="1" /> <g:submitToRemote action="delete" update="[success:'message'.2 Ajax with Dojo Grails features an external plug-in to add Dojo support to Grails.failure:'error']" /> </form> 6. With that done you 142 .failure:'error']"> <input type="hidden" name="id" value="1" /> <input type="submit" value="Delete Book!" /> </g:formRemote > Or alternatively you can use the submitToRemote tag to create a submit button. all the events start with the "on" prefix and allow you to give feedback to the user where appropriate.The javascript function to call if successful onFailure .7. To install the plug-in type the following command from the root of your project in a terminal window: grails install-plugin dojo This will download the current supported version of Dojo and install it into your Grails project.action:'delete']" update="[success:'message'.4 Ajax Events Specific javascript can be called if certain events occur.
6.id}"> <!--existing book mark-up --> </div> Data Centric Ajax with JSON Data Centric Ajax typically involves evaluating the response on the client and updating programmatically. but you may also want to use Data Centric or Script Centric.get(params. formRemote and submitToRemote work with Dojo remoting.7.Where the server sends down a stream of Javascript to be evaluated on the fly Most of the examples in the Ajax section cover Content Centric Ajax where you are updating the page.get(params.converters.4 Ajax on the Server Although Ajax features the X for XML there are a number of different ways to implement Ajax which are typically broken down into: Content Centric Ajax . This guide covers the different styles of Ajax.Where you actually send an XML or JSON response from the server and programmatically update the page Script Centric Ajax .id}" update="book${book. Content Centric Ajax Just to re-cap.7. content centric Ajax involves sending some HTML back from the server and is typically done by rendering a template with the render method: def showBook = { def b = Book.id}">Update Book</g:remoteLink> <div id="book${book. 6.id) render(template:"bookTemplate".id) render b as JSON } And then on the client parse the incoming JSON request using an Ajax event handler: 143 .3 Ajax with GWT Grails also features support for the Google Web Toolkit through a plug-in comprehensive documentation for can be found on the Grails wiki.Where you merely use the HTML result of a remote call to update the page Data Centric Ajax .can add the following reference to the top of your page: <g:javascript library="dojo" /> Now all of Grails tags such as remoteLink.* def showBook = { def b = Book. model:[book:b]) } Calling this on the client involves using the remoteLink tag: <g:remoteLink action="showBook" id="${book. For a JSON response with Grails you would typically use Grails' JSON marshaling capability: import grails.
getElementsByTagName("title")[0].converters.title. By default Grails comes configured with a number of different content types within 144 .id) render b as XML } However.id}</g:set> <div id="${bookId}"> <div id="${bookId}_title">The Stand</div> </div> Data Centric Ajax with XML On the server side using XML is equally trivial: import grails.id}</g:set> <div id="${bookId}"> <div id="${bookId}_title">The Stand</div> </div> Script Centric Ajax with JavaScript Script centric Ajax involves actually sending Javascript back that gets evaluated on the client.title } <g:javascript> <g:remoteLink action="test" update="foo" onSuccess="updateBook(e)">Update Book</g:remoteLink> <g:set var="bookId">book${book.getAttribute("id") $("book" + id + "_title") = xml.get(params.8 Content Negotiation Grails has built in support for Content negotiation using either the HTTP Accept header.innerHTML = book.encodeAsJavascript() render "$('book${b. since DOM is involved the client gets more complicated: <g:javascript> function updateBook(e) { var xml = e. This is one of the reasons Rails has something like RJS. If you are using Prototype on the client the returned Javascript will automatically be evaluated due to this contentType setting. Although Grails does not currently have a feature such as RJS there is a Dynamic JavaScript Plug-in that offers similar capabilities.id + "_title").responseText+")") // evaluate the JSON $("book" + book.responseXML var id = xml.id) response.* def showBook = { def b = Book. 6. Configuring Mime Types Before you can start dealing with content negotiation you need to tell Grails what content types you wish to support. Obviously in this case it is critical that you have an agreed client-side API as you don't want changes on the client breaking the server.getElementsByTagName("book").contentType = "text/javascript" String title = b.get(params. An example of this can be seen below: def showBook = { def b = Book.id}_title')='${title}'" } The important thing to remember is to set the contentType to text/javascript.textContent } <g:javascript> <g:remoteLink action="test" update="foo" onSuccess="updateBook(e)">Update Book</g:remoteLink> <g:set var="bookId">book${book. an explicit format request parameter or the extension of a mapped URI.<g:javascript> function updateBook(e) { var book = eval("("+e.
params.void testJavascriptOutput() { def controller = new TestController() controller.response.contentAsString } 147 .format = 'js' controller.testAction() assertEquals "alert('hello')". controller.
errors. static constraints = { login(size:5.allErrors. However Grails takes this further and provides a unified way to define validation "constraints" with its constraints mechanism. Most commonly they are applied to domain classes. Constraints in Grails are a way to declaratively specify validation rules... Validation Phases 148 .15. email and age properties. blank:false. A complete reference for the available constraints can be found on the reference guide 7..7. Validation Grails validation capability is built on Spring's Validator API and data binding capabilities. The Errors interface provides methods to navigate the validation errors and also retrieve the original values. unique:true) password(size:5. it cannot be blank and must be unique. however URL Mappings and Command Objects also support constraints.2 Validating Constraints Validation Basics To validate a domain class you can call the validate method on any instance: def user = new User(params) if(user.1 Declaring Constraints Within a domain class a constraints are defined with the constraints property that is assigned a code block: class User { String login String password String email Integer age static constraints = { … } } You then use method calls that match the property name for which the constraint applies in combination with named parameters to specify constraints: class User { . We've all applied other constraints to the password. blank:false) age(min:18.each { println it } } The errors property on domain classes is an instance of the Spring Errors interface.15. 7. nullable:false) } } In this example we've declared that the login property must be between 5 and 15 characters long. blank:false) email(email:true..validate()) { // do something with user } else { user.
rejectedValue } } The second phase of validation happens when you call validate or save.'errors')}'> <input type="text" name="login" value="${fieldValue(bean:user.field:'login'. This is when Grails will validate the bound values againts the constraints you defined. You can check these and obtain the original input value using the Errors API: if(user.errors. Once there you need some way of rendering errors. If you simply want to render the errors as a list you can use renderErrors: <g:renderErrors bean="${user}" /> If you need more control you can use hasErrors and eachError: <g:hasErrors bean="${user}"> <ul> <g:eachError var="err" bean="${user}"> <li>${err}</li> </g:eachError> </ul> </g:hasErrors> Highlighting Errors It is often useful to highlight using a red box or some indicator when a field has been incorrectly input.allErrors.errors.save()) { return user } else { user. For example: <div class='value ${hasErrors(bean:user. the first phase is data binding which occurs when you bind request parameters onto an instance such as: def user = new User(params) At this point you may already have errors in the errors property due to type conversion (such as converting Strings to Dates).3 Validation on the Client Displaying Errors Typically if you get a validation error you want to redirect back to the view for rendering.hasFieldErrors("login")) { println user. For example.field:'login')}"/> </div> 149 . by default the persistent save method calls validate before executing hence allowing you to write code like: if(user. Grails supports a rich set of tags for dealing with errors.errors.each { println it } } 7.hasErrors()) { if(user.Within Grails there are essentially 2 phases of validation. This can also be done with the hasErrors by invoking it as a method.getFieldError("login").
. blank:false. This is useful as you can use the error object to restore the value input by the user using the fieldValue tag: <input type="text" name="login" value="${fieldValue(bean:user. Displaying Messages The renderErrors tag will automatically deal with looking up messages for you using the message tag. by convention.mycompany.myapp class User { ..What this code does is check if the login field of the user bean has any errors and if it does adds an errors CSS class to the div thus allowing you to use CSS rules to highlight the div. For a reference on what codes are for which constraints refer to the reference guide for each constraint.blank so you would need a message such as the following in your grails-app/i18n/messages. look for a message code in the form: [Class Name].[Constraint Code] In the case of the blank constraint this would be user.properties file: user. if you need more control of rendering you will need to do this yourself: 150 .15. com. with the packaged version taking precedence..mycompany.myapp.login. unique:true) password(size:5.login.15. The FieldError class in Spring essentially resolves messages from message bundles using Grails' i18n support.field:'login')}"/> This code will look if there is an existing FieldError in the User bean and if there is obtain the originally input value for the login field.blank=Your login name must be specified! The class name is looked for both with and without a package. So for example. However.blank. Retrieving Input Values Each error is actually an instance of the FieldError class in Spring.login.4 Validation and Internationalization Another important thing to note about errors in Grails is that the messages that the errors display are not hard coded anywhere. 7. Constraints and Message Codes The codes themselves are dictated by a convention. For example consider the constraints we looked at earlier: package com. blank:false) age(min:18.blank will be used before user. nullable:false) } } If the blank constraint was violated Grails will.[Property Name]. blank:false) email(email:true.login. static constraints = { login(size:5.. This allows for cases where you domain class encounters message code clashes with plugins. which retains the original input value within it.User.
Account] .myapp import org.. blank:false) email(email:true.classes property in Config. Consider this example: // src/groovy/com/mycompany/myapp/User. Simply defining the constraints property is not sufficient.groovy .5 Validation Non Domain and Command Object Classes Domain classes and command objects support validation by default...<g:hasErrors bean="${user}"> <ul> <g:eachError var="err" bean="${user}"> <li><g:message error="${err}" /></li> </g:eachError> </ul> </g:hasErrors> In this example within the body of the eachError tag we use the message tag in combination with its error argument to read the message for the given error.validateable.. it may still be made validateable by the framework.User.validateable. grails..15. // grails-app/conf/Config. Registering Validateable Classes If a class is not marked with @Validateable. grails.mycompany.groovy ..groovy.mycompany.groovy.mycompany.15...validation. blank:false) age(min:18. 7..dto'. com. blank:false.validateable.util'] .mycompany. static constraints = { login(size:5.groovy.codehaus. The Validateable Annotation Classes which define the static constraints property and are marked with the @Validateable annotation may be made validateable by the framework. The framework will only search those packages (and child packages of those) for classes marked with @Validateable.groovy package com.. 'com.myapp.validateable.. It is important that the application register the validateable classes with the framework. Other classes may be made validateable by defining the static constraints property in the class (as described above) and then telling the framework about them. // grails-app/conf/Config. nullable:false) } } You need to tell the framework which packages to search for @Validateable classes by assigning a list of Strings to the grails. unique:true) password(size:5.packages = ['com.dto.packages property in Config.. The steps required to do this are to define the static constraints property in the class (as described above) and then telling the framework about the class by assigning a value to the grails.classes = [com. 151 .grails.mycompany.Validateable @Validateable class User { .
or simply to make it clear that the service is intentionally transactional. The Service Layer As well as the Web layer. other than that a service is a plain Groovy class: class SimpleService { } 8. Grails defines the notion of a service layer.to disable it. Custom Transaction Configuration Grails also fully supports Spring's Transactional annotation for cases where you need more fine-grained control over transactions at a per-method level or need specify an alternative propagation level: 152 . Given the nature of services they frequently require transactional behaviour. simply set the transactional property to false: class CountryService { static transactional = false } You may also set this property to true in case the default changes in the future. leaving controllers responsible for handling request flow via redirects and so on. All services have transaction demarcation enabled by default . as it does not promote re-use and a clean separation of concerns. You can of course use programmatic transactions with the withTransaction method. which is essentially a declarative way of saying all methods within this service are to be made transactional. Services in Grails are seen as the place to put the majority of the logic in your application. The Grails team discourages the embedding of core application logic inside controllers. and hence often involved with persistence that spans large operations.groovy.8. The propagation level of the transaction is by default set to PROPAGATION_REQUIRED. however this is repetitive and doesn't fully leverage the power of Spring's underlying transaction abstraction. Services allow the enablement of transaction demarcation. A service's name ends with the convention Service. Creating a Service You can create a Grails service by running the create-service command from the root of your project in a terminal window: grails create-service simple The above example will create a service at the location grails-app/services/SimpleService.1 Declarative Transactions Default Declarative Transactions Services are typically involved with co-ordinating logic between domain classes. Warning: dependency injection is the only way that declarative transactions work. You will not get a transactional service if you use the new operator such as new BookService() The result is all methods are wrapped in a transaction and automatic rollback occurs if an exception is thrown in the body of one of the methods.
you can use the property name representation of the class name of a service.annotation. ie a root flow and its sub flows session .3 Dependency Injection and Services Dependency Injection Basics A key aspect of Grails services is the ability to take advantage of the Spring Framework's dependency injection capability. if you place a property called bookService within a controller as follows: class BookController { def bookService … } In this case. to automatically inject them into controllers. In fact.io. you should be very careful about storing state in a service. Or take the easy (and better) road and never store state in a service. access to service methods is not synchronised. In other words. You can also specify the type as follows: 153 .A new service will be created for the current and next request only flow . because the service is a singleton and may be used concurrently. the Spring container will automatically inject an instance of that service based on its configured scope.A new service will be created per request flash .list() } @Transactional def updateBook() { // … } } For more information refer to the section of the Spring user guide on Using @Transactional.import org. add a static scope property to your class whose value is one of the above: static scope = "flow" 8.springframework.transaction.* class BookService { @Transactional(readOnly = true) def listBooks() { Book. As an example. and so on.A new service is created every time it is injected into another class request .In web flows the service will exist for the scope of the flow conversation . Unlike Spring you do not need any prior configuration to use Transactional.Only one instance of the service ever exists If your service is flash. Grails supports "dependency injection by convention".In web flows the service will exist for the scope of the conversation. so nothing prevents concurrent execution of those functions. The supported scopes are: prototype . given a service called BookService. tag libraries. 8. just specify the annotation as needed and Grails will pick them up automatically. You can change this behaviour by placing a service in a particular scope.A service is created for the scope of a user session singleton (default) . flow or conversation scoped it will need to implement java.2 Scoped Services By default.Serializable and can only be used in the context of a Web Flow To enable one of the scopes. All dependency injection is done by name.
So for example the BookService below cannot be used from Java as it stands: class BookService { void buyBook(Book book) { // logic } } However. an instance of the BookService class would map to a property named bookService. you can use them from other classes.buyBook(this) } } 8. For example. The reason this is a critical step is that it is not possible to import classes into Java from the default package (the package used when no package declaration is present). There are a couple of ways you can re-use a service from Java. an instance of the MYhelperService class would map to a property named MYhelperService. To be consistent with standard JavaBean convetions. this can be rectified by placing this class in a package. declaring the AuthorService as follows would allow that: class AuthorService { def bookService } Dependency Injection and Domain Classes You can even inject services into domain classes. by moving the class into a sub directory such as grails-app/services/bookstore and then modifying the package declaration: package bookstore class BookService { void buyBook(Book book) { // logic } } 154 . Dependency Injection and Services You can inject services in other services with the same technique. The simplest way is to move your service into a package within the grails-app/services directory.8 of the JavaBean specification for more information on de-capitalization rules.4 Using Services from Java One of the powerful things about services is that since they encapsulate re-usable logic. which can aid in the development of rich domain models: class Book { … def bookService def buyBook() { bookService. See section 8.class AuthorService { BookService bookService } NOTE: Normally the property name is generated by lower casing the first letter of the type. if the first 2 letters of the class name are upper case. including Java classes. Say you had an AuthorService that needed to use the BookService. For example. the property name is the same as the class name.
at compile time.An alternative to packages is to instead have an interface within a package that the service implements: package bookstore. public void setBookStore(BookStore storeInstance) { this.xml (For more information one this see the section on Grails and Spring): <bean id="bookConsumer" class="bookstore.store = storeInstance. as the Java side only has a reference to the interface and not to the implementation class.BookConsumer"> <property name="bookStore" ref="bookService" /> </bean> 155 . } … } Once this is done you can configure the Java class as a Spring bean in grails-app/conf/spring/resources. and provide a setter that uses the type and the name of the bean in Spring: package bookstore.BookStore { void buyBook(Book b) { // logic } } This latter technique is arguably cleaner. Now that this is done you can create a Java class within the src/java package. Either way. // note: this is Java class public class BookConsumer { private BookStore store. interface BookStore { void buyBook(Book book). the goal of this exercise to enable Java to statically resolve the class (or interface) to use. } And then the service: class BookService implements bookstore.
To run all tests for a controller named SimpleController you would run: grails test-app SimpleController This will run any tests for the class named SimpleController.yourcompany. implemented using Groovy Tests.groovy. The first thing to be aware of is that all of the create-* commands actually end up creating unit tests automatically for you.groovy.FAILURE Unit Tests Completed in 464ms … ------------------------------------------------------Tests failed: 0 errors. Grails provides many ways to making testing easier from low level unit testing to high level functional tests. As of Grails 1. Targeting Tests You can selectively target the test(s) to be run in different ways. grails test-app *Controller 156 ..2. 1 failures Whilst reports will have been written out the target/test-reports directory.the suffix of Test is also supported for test cases.9.yourapp. For example say you run the create-controller command as follows: grails create-controller com. Testing Automated testing is seen as a key part of Grails. What Grails won't do however is populate the logic inside the test! That is left up to you. but also an unit test at test/unit/com/yourcompany/yourapp/SimpleControllerTests... Running Tests Test are run with the test-app command: grails test-app The above command will produce output such as: ------------------------------------------------------Running Unit Tests… Running test FooTests. Hence.simple Not only will Grails create a controller at grails-app/controllers/com/yourcompany/yourapp/SimpleController. This section details the different capabilities that Grails offers in terms of testing. You can force a clean before running tests by passing -clean to the test-app command.2. Wildcards can be used..
. functional and other) and JUnit test types for the unit and integration phases.org. integration and functional phases. you can also target test types and/or phases by using the phase:type syntax. A test phase relates to the state of the Grails application during the tests. Grails comes with support for 4 test phases (unit.. grails test-app SimpleController.testLogin This will run the testLogin test in the SimpleController tests. You can specify as many patterns in combination as you like. The following command will run all test types in the unit phase: grails test-app unit: The Grails Spock Plugin is one plugin that adds new test types to Grails.This will test all classes ending in Controller. grails test-app some.org. and the type relates to the testing mechanism. To run all spock tests in all phases you would run the following: 157 .** You can also target particular test methods. integration. Testing plugins may provide new test phases or new test types for existing phases.org.. grails test-app some..testLogin BookController Targeting Test Types and/or Phases In addition to targeting certain tests..org..* SimpleController.. Their absence acts as a wildcard. Refer to the plugin documentation. These test types have the same name as the phase. grails test-app some. grails test-app some..* or to run all tests in a package including subpackages. It adds a spock test type to the unit...*Controller or to run all tests in a package. To execute the JUnit integration tests you can run: grails test-app integration:integration Both phase and type are optional. Grails organises tests by phase and by type. Package names can optionally be specified.
This makes sense if you consider that the methods injected by Grails typically communicate with the database (with GORM) or the underlying Servlet engine (with Controllers).test. In other words you are testing individual methods or blocks of code without considering for surrounding infrastructure.GrailsUnitTestCase class.org. How might we write the test with GrailsUnitTestCase ? 158 .org or a subpackage of. name: "Bangle") item.. grails test-app unit:spock integration:spock Targeting Tests in Types and/or Phases Test and type/phase targetting can be applied at the same time: grails test-app integration: unit: some. It provides several methods for mocking particular types as well as support for general mocking a la Groovy's MockFor and StubFor classes. The Testing Framework The core of the testing plugin is the grails. Normally you might look at the MyService example shown previously and the dependency on another service and the use of dynamic domain class methods with a bit of a groan.grails test-app :spock To run the all of the spock tests in the functional phase you would run.. So how do you go about testing the above code in a unit test? The answer can be found in Grails' testing support classes.size() } } As you can see the service takes advantage of GORM methods.** This would run all tests in the integration and unit phases that are in the page some. This is a sub-class of GroovyTestCase geared towards Grails applications and their artifacts.newIdentifier() def item = new Item(code: stringId. 9. grails test-app functional:spock More than one pattern can be specified. For example say you have service like the following in BookController: class MyService { def otherService String createSomething() { def stringId = otherService.. but these can quickly get ugly. You can use meta-class programming and the "map as object" idiom.1 Unit Testing Unit testing are tests at the "unit" level.findAllByName(name) return items.. In Grails you need to be particularity aware of the difference between unit and integration tests because in unit tests Grails does not inject any of the dynamic methods present during integration tests and at runtime.save() return stringId } int countItems(String name) { def items = Item.
which is one of several provided by GrailsUnitTestCase: def testInstances = [] mockDomain(Item. retval assertEquals 1. So for example. Song. void testSomething() { def testInstances=[] mockDomain(Song. testInstances) assertEquals(0.newIdentifier(1. we can safely call the save() method on instances of it.newIdentifier(1.save() assertEquals(1.demand. testInstances. Song. Take a look at the "testCreateSomething()" test method. def testInstances = Item. Of course you often need to inject a mock instance as a dependency. but that is pretty straight forward with the 159 . The first thing you will probably notice is the mockDomain() method.count()) new Song(name:"Supper's Ready").countItems("Lamp") assertEquals 0. Invoking the save() method doesn't really save the instance to any database but it will cache the object in the testing framework so the instance will be visible to certain queries.createSomething() // Check that the method returns the identifier returned by the // mock "other" service and also that a new Item instance has // been saved. once the Item class has been mocked.list() assertEquals testId. def testService = new MyService() testService. testService. this time providing a list of test // Item instances that can be searched. The following code snippet demonstrates the effect of calling the save() method.1) {-> return testId } This is analagous to the MockFor and StubFor classes that come with Groovy and it can be used to mock any class you want. testService.test.import grails.otherService = otherControl.createMock() def retval = testService. mockDomain(Item) // Mock the "other" service.1) {-> return testId } // Initialise the service and test the target method. new Item(code: "EC-4395734". name: "Laptop") ] mockDomain(Item.size() assertTrue testInstances[0] instanceof Item } void testCountItems() { // Mock the domain class. name: "Lamp").. new Item(code: "TF-4927324".GrailsUnitTestCase class MyServiceTests extends GrailsUnitTestCase { void testCreateSomething() { // Mock the domain class. but once we break it down you should quickly see how easy it is to use the methods available to you.countItems("Laptop") assertEquals 1. In fact. so you should feel right at home.countItems("Chair") } } OK.. name: "Laptop"). testInstances) It adds all the common domain methods (both instance and static) to the given class so that any code using it sees it as a full-blown domain class. so a fair bit of new stuff there.demand. String testId = "NH-12347686" def otherControl = mockFor(OtherService) otherControl. def testInstances = [ new Item(code: "NH-4273997". def testService = new MyService() assertEquals 2. testService. the "demand" syntax is identical to that used by Mock/StubFor.count()) } The next bit we want to look at is centered on the mockFor method: def otherControl = mockFor(OtherService) otherControl. testInstances) // Initialise the service and test the target method.
i. name: "Laptop") ] mockDomain(Item. name: "Lamp"). This method is surprisingly intuitive to use..e. if you decide a different finder should be used then you have to update the tests to check for the new method! Thankfully the mockDomain() method provides a lightweight implementation of the dynamic finders backed by a list of domain instances. And once you have executed the test method. mockFor(class.2) { String arg1. but that's not available here.() methods on each class you want to mock. there is an important technique missing from the test method. You then specify the name of the method that you want to mock with an optional range as its argument. testInstances) It is normally quite fiddly to mock the dynamic finders manually. If no range is specified. We can determine that the mock newIdentifier() method is called because its return value has a direct impact on the result of the createSomething() method. By default it will create a strict mock control object (one for which the order in which methods are called is important) that you can use to specify demands: def strictControl = mockFor(MyService) strictControl. new Item(code: "EC-4395734". Lastly. The rest of the testCreateSomething() method should be pretty familiar. The closure arguments should match the number and types of the mocked method.verify() to check whether the expected methods were actually called or not. Instead. For those familiar with EasyMock. but that headache just disappears as long as you use at least one of mock.the mock methods You have already seen a couple of examples in the introduction of the mock.createMock(). there is a very important point to make: using these methods ensures that any changes you make to the given classes do not leak into other tests! This is a common and serious problem when you try to perform the mocking yourself via meta-class programming. The last part of a demand is a closure representing the implementation of the mock method. which you simply call on the mock control as shown. you can call this as many times as you like to create as many mock instances as you need.static.1" is assumed. the call: 160 . you can call mockControl. Here we will look at all the available methods in some detail. This will perform the check and throw an assertion error if it hasn't been called when it should have been.. if you want an actual mock instance of the class that you are mocking. you can call verify() on the control object in this case otherControl. GrailsUnitTestCase . But what if that weren't the case? How would we know whether it had been called or not? With Mock/StubFor the check would be performed at the end of the use() closure..aStaticMethod {-> … } Notice that you can mock static methods as well as instance ones simply by using the "static" property after "demand".() methods provided by the GrailsUnitTestCase class. As we mentioned before. new Item(code: "TF-4927324". In fact. loose = false) General purpose mocking that allows you to set up either strict or loose demands on a class. Lastly. the name otherControl highlights the role of the object returned by mockFor() . name: "Laptop"). Simply provide the test data as the second argument of the method and the mock finders will just work. However. a default of "1. then you need to call mockControl. particularly as you now know that the mock save() method adds instances to testInstances list.demand. int arg2 -> … } strictControl.. that the method must be called exactly once. and you often have to set up different data sets for each invocation. This range determines how many times you expect the method to be called.createMock() method. so if the number of invocations falls outside of that range (either too few or too many) then an assertion error will be thrown. On top of that.demand.someMethod(0.it is a control object rather than the mock itself. testCountItems() in the example demonstrates another facet of the mockDomain() method: def testInstances = [ new Item(code: "NH-4273997". but otherwise you are free to add whatever you want in the body. But before we do. starting with the all-purpose mockFor().
suppose we have a simple domain class like so: class Book { String title String author static constraints = { title(blank: false.) work against that list. unique: true) author(blank: false. There isn't much else to say other than that the plugin does not support the mocking of criteria or HQL queries. get() . This is like a much reduced version of the mockDomain() method that simply adds a validate() method to a given domain class. why the optional list of test instances? That is so that we can test unique constraints as you will soon see. minSize: 5) } } Don't worry about whether the constraints are sensible or not (they're not!). they are for demonstration only. generally behaving as you would expect them to. simply mock the corresponding methods manually (for example with mockFor() ) or use an integration test with real data. All you have to do is mock the class. mockForConstraintsTests(class. etc. create an instance with field values. You can then access the errors property on your domain instance to find out whether the validation failed or not. and then call validate(). i. All the mocked methods ( save() .def looseControl = mockFor(MyService. think again. So if all we are doing is mocking the validate() method. true) will create a mock control object that has only loose expectations. so it's great that mockDomain() takes that burden off your shoulders.e.the kind of bugs that can be tricky to track down (particularly as save() doesn't throw an exception when it fails). Enter the mockForConstraintsTests() method. why not? If your answer is that they don't need testing. If your answer is that it's too hard or fiddly. testInstances = ) Takes a class and makes mock implementations of all the domain class methods (both instance. findBy*() . testInstances = ) Highly specialised mocking for domain classes and command objects that allows you to check whether the constraints are behaving as you expect them to. that is no longer an excuse. Your constraints contain logic and that logic is highly susceptible to bugs . If you use either of those. Manually doing it is fiddly at best. To test these constraints we can do the following: 161 . both the mocked save() and validate() methods will perform real validation (support for the unique constraint included!) and populate an errors object on the corresponding domain instance. mockDomain(class.and static-level) accessible on it. In effect. mockDomain() provides a lightweight version of domain classes in which the "database" is simply a list of domain instances held in memory. In addition to that. Mocking domain classes is one of the big wins from using the testing plugin. Do you test your domain constraints? If not. the order that methods are invoked does not matter. So.
MockHttpServletResponse. This is typically used in conjunction with the TagLibUnitTestCase class. Any messages passed to the mock logger are echoed to the console. Testing Controllers To test controllers you first have to understand the Spring Mock Library. mockController(class) Adds mock versions of the dynamic controller properties and methods to the given class. book.errors["title"] assertEquals "nullable". mockLogging(class. it does return a real Spring Errors instance. enableDebug = false) Adds a mock "log" property to a class. For example consider the following controller: class FooController { def text = { render "bar" } def someRedirect = { redirect(action:"bar") } } The tests for this would be: 162 .class BookTests extends GrailsUnitTestCase { void testConstraints() { def existingBook = new Book(title: "Misery".validate() assertEquals "nullable".errors["author"] // So let's demonstrate the unique and minSize constraints.2 Integration Testing Integration tests differ from unit tests in that you have full access to the Grails environment within the test. this particular Errors object also has map/property access as shown. The one thing we will explain is the way the errors property is used. mockTagLib(class) Adds mock versions of the dynamic taglib properties and methods to the given class. so you can access all the properties and methods you would normally expect. This is typically used in conjunction with the ControllerUnitTestCase class. author: "Stephen King") assertTrue book. 9. not the message code (as you might expect). That's it for testing constraints. book = new Book(title: "Misery".errors["title"] assertEquals "minSize". Second.validate() assertEquals "unique". First. One final thing we would like to say is that testing the constraints in this way catches a common error: typos in the "constraints" property! It is currently one of the hardest bugs to track down normally. and MockHttpSession which you can then use to perform your tests. def book = new Book() assertFalse book.validate() } } You can probably look at that code and work out what's happening without any further explanation. book. Grails will use an in-memory HSQLDB database for integration tests and clear out all the data from the database in between each test. book. [ existingBook ]) // Validation should fail if both properties are null.errors["author"] // Validation should pass! book = new Book(title: "The Shining". author: "JK") assertFalse book. and yet a unit test for your constraints will highlight the problem straight away. Essentially Grails automatically configures each test with a MockHttpServletRequest. Note that it is the constraint name . author: "Stephen King") mockForConstraintsTests(Book. book. Simply specify the name of the field you are interested in and the map/property access will return the name of the constraint that was violated.
text() assertEquals "bar".contentAsString } void testSomeRedirect() { def fc = new FooController() fc.update() } } Testing Controller Command Objects With command objects you just supply parameters to the request and it will automatically do the command object work for you when you call your action with no parameters: Given a controller using a command object: class AuthenticationController { def signup = { SignupForm form -> … } } You can then test it like this: 163 .redirectedUrl } } In the above case the response is an instance of MockHttpServletResponse which we can use to obtain the contentAsString (when writing to the response) or the URL redirected to for example. These mocked versions of the Servlet API are. Testing Controllers with Services If your controller references a service (or other Spring beans). Grails does not invoke interceptors or servlet filters automatically when calling actions during integration testing. and via functional testing if necessary.response. fc. fc. You should test interceptors and filters in isolation. Given a controller using a service: class FilmStarsController { def popularityService def update = { // do something with popularityService } } The test for this would be: class FilmStarsTests extends GroovyTestCase { def popularityService void testInjectedServiceInController () { def fsc = new FilmStarsController() fsc.popularityService = popularityService fsc.response. unlike the real versions.someRedirect() assertEquals "/foo/bar".class FooControllerTests extends GroovyTestCase { void testText() { def fc = new FooController() fc. all completely mutable and hence you can set properties on the request such as the contextPath and so on. you have to explicitly initialise the service from your test.
passwordConfirm = "secret" controller.create() assert model. During controller testing. consider the example below: def save = { def book = Book(params) if(book.password = "secret" controller. For instance.request.def controller = new AuthenticationController() controller.title } The same can be achieved with a JSON request: 164 . model:[book:book]) } } In the above example the result of the model of the action is not available as the return value.save() def model = bookController. but instead is stored within the modelAndView property of the controller.save()) { // handle } else { render(view:"create".modelAndView. For example consider this action which performs data binding from an incoming request: def create = { [book: new Book(params['book']) ] } If you wish the simulate the 'book' parameter as an XML request you could do something like the following: void testCreateWithXML() { def controller = new BookController() controller.signup() Grails auto-magically sees your call to signup() as a call to the action and populates the command object from the mocked request parameters.book Simulating Request Data If you're testing an action that requires request data such as a REST web service you can use the Spring MockHttpServletRequest object to do so.params.0" encoding="ISO-8859-1"?> <book> <title>The Stand</title> … </book> '''.login = "marcpalmer" controller. model.model. The modelAndView property is an instance of Spring MVC's ModelAndView class and you can use it to the test the result of an action: def bookController = new BookController() bookController.params.book assertEquals "The Stand". the params are mutable with a mocked request supplied by Grails.content = '''<?xml version="1. Testing Controllers and the render Method The render method allows you to render a custom view at any point within the body of an action.params.book.contentType = 'text/xml' controller.request.getBytes() // note we need the bytes def model = controller.
For more information on the subject of REST web services see the section on REST.exampleFlow } … } If you need to specify the flow id you can do so by overriding the getFlowId method otherwise the default is test: class ExampleFlowTests extends grails.title } With JSON don't forget the class property to specify the name the target type to bind too.getBytes() def model = controller.book.create() assert model.request.contentType = "text/json" controller.test.content = '{"id":1.request. model. This is done via overriding the abstract getFlow method: class ExampleFlowTests extends grails. Testing Web Flows Testing Web Flows requires a special test harness called grails. but with JSON you need this property as part of the JSON packet."title":"The Stand"}'.WebFlowTestCase which sub classes Spring Web Flow's AbstractFlowExecutionTests class. Subclasses of WebFlowTestCase must be integration tests For example given this trivial flow: class ExampleController { def exampleFlow = { start { on("go") { flow.to "end" } end() } } You need to tell the test harness what to use for the "flow definition"."class":"Book".to "next" } next { on("back").void testCreateWithJSON() { def controller = new BookController() controller.test.WebFlowTestCase { String getFlowId() { "example" } … } Once this is done in your test you need to kick off the flow with the startFlow method which returns a ViewSelection object: 165 . In the XML this is implicit within the name of the <book> node.WebFlowTestCase { def getFlow() { new ExampleController().hello = "world" }.to "start" on("go").book assertEquals "The Stand".test.
void testExampleFlow() { def viewSelection = startFlow() assertEquals "start", viewSelection.viewName … }
As demonstrated above you can check you're on the right state using the viewName property of the ViewSelection object. To trigger and event you need to use the signalEvent method:
void testExampleFlow() { … viewSelection = signalEvent("go") assertEquals "next", viewSelection.viewName assertEquals "world", viewSelection.model.hello }
Here we have signaled to the flow to execute the event "go" this causes a transition to the "next" state. In the example a transition action placed a hello variable into the flow scope. We can test the value of this variable by inspecting the model property of the ViewSelection as above. Testing Tag Libraries Testing tag libraries is actually pretty trivial because when a tag is invoked as a method it returns its result as a string. So for example if you have a tag library like this:
class FooTagLib { def bar = { attrs, body -> out << "<p>Hello World!</p>" } def bodyTag = { attrs, body -> out << "<${attrs.name}>" out << body() out << "</${attrs.name}>" } }
The tests would look like:
class FooTagLibTests extends GroovyTestCase { void testBarTag() { assertEquals "<p>Hello World!</p>", new FooTagLib().bar(null,null).toString() } void testBodyTag() { assertEquals "<p>Hello World!</p>", new FooTagLib().bodyTag(name:"p") { "Hello World!" }.toString() } }
Notice that for the second example, testBodyTag, we pass a block that returns the body of the tag. This is handy for representing the body as a String. Testing Tag Libraries with GroovyPagesTestCase In addition to doing simply testing of tag libraries like the above you can also use the grails.test.GroovyPagesTestCase class to test tag libraries. The GroovyPagesTestCase class is a sub class of the regular GroovyTestCase class and provides utility methods for testing the output of a GSP rendering.
GroovyPagesTestCase can only be used in an integration test.
As an example given a date formatting tag library such as the one below:
class FormatTagLib { def dateFormat = { attrs, body -> out << new java.text.SimpleDateFormat(attrs.format) << attrs.date } }
This can be easily tested as follows:
class FormatTagLibTests extends GroovyPagesTestCase { void testDateFormat() { def template = '<g:dateFormat format="dd-MM-yyyy" date="${myDate}" />' def testDate = … // create the date assertOutputEquals( '01-01-2008', template, [myDate:testDate] ) } }
You can also obtain the result of a GSP using the applyTemplate method of the GroovyPagesTestCase class:
class FormatTagLibTests extends GroovyPagesTestCase { void testDateFormat() { def template = '<g:dateFormat format="dd-MM-yyyy" date="${myDate}" />' def testDate = … // create the date def result = applyTemplate( template, [myDate:testDate] ) assertEquals '01-01-2008', result } }
Testing Domain Classes Testing domain classes is typically a simple matter of using the GORM API, however there are some things to be aware of. Firstly, if you are testing queries you will often need to "flush" in order to ensure the correct state has been persisted to the database. For example take the following example:
void testQuery() { def books = [ new Book(title:"The Stand"), new Book(title:"The Shining")] books*.save() assertEquals 2, Book.list().size() }
This test will actually fail, because calling save does not actually persist the Book instances when called. Calling save merely indicates to Hibernate that at some point in the future these instances should be persisted. If you wish to commit changes immediately you need to "flush" them:
void testQuery() { def books = [ new Book(title:"The Stand"), new Book(title:"The Shining")] books*.save(flush:true) assertEquals 2, Book.list().size() }
In this case since we're passing the argument flush with a value of true the updates will be persisted immediately and hence will be available to the query later on.
9.3 Functional Testing
Functional tests involve testing the actual running application and are often harder to automate. Grails does not ship
with any functional testing support out of the box, but has support for Canoo WebTest via a plug-in. To get started install Web Test with the following commands:
grails install-plugin webtest
Then refer to the reference on the wiki which explains how to go about using Web Test and Grails.
10. Internationalization
Grails supports Internationalization (i18n) out of the box through the underlying Spring MVC support for internationalization. With Grails you are able to customize the text that appears in any view based on the users Locale. To quote the javadoc for the Locale class in Java: A Locale object represents a specific geographical, political, or cultural region. An operation that requires a Locale to perform its task is called locale-sensitive and uses the Locale to tailor information for the user. For example, displaying a number is a locale-sensitive operation--the number should be formatted according to the customs/conventions of the user's native country, region, or culture. A Locale is made up of a language code and a country code. For example "en_US" is the code for US english, whilst "en_GB" is the for British English.
10.1 Understanding Message Bundles
Now that you have an idea of locales, to take advantage of them in Grails you have to create message bundles that contain the different languages that you wish to render. Message bundles in Grails are located inside the grails-app/i18n directory and are simple Java properties files. Each bundle starts with the name messages by convention and ends with the locale. Grails ships with a bunch of built in message bundles for a whole range of languages within the grails-app/i18n directory. For example:
messages.properties messages_de.properties messages_es.properties etc.
By default Grails will look in messages.properties for messages, unless the user has specified a custom locale. You can create your own message bundle by simply creating a new properties file that ends with the locale you are interested. For example messages_en_GB.properties for British English.
10.2 Changing Locales
By default the user locale is detected from the incoming Accept-Language header. However, you can provide users the capability to switch locales by simply passing a parameter called lang to Grails as a request parameter:
Grails will automatically switch the user locale and store it in a cookie so subsequent requests will have the new header.
10.3 Reading Messages
Reading Messages in the View The most common place that you need messages is inside the view. To read messages from the view just use the message tag:
<g:message code="my.localized.content" />
As long as you have a key in your messages.properties (with appropriate locale suffix) such as the one below then Grails will look-up the message:
my.localized.content=Hola, Me llamo John. Hoy es domingo.
Note that sometimes you may need to pass arguments to the message. This is also possible with the message tag:
prefix: def myTag = { attrs. 'lunes']) } The same technique can be used on tag libraries.4 Scaffolding and i18n Grails does not ship with i18n aware scaffolding templates to generate the controller and views. However. 'lunes'] }" /> And then use positional parameters in the message: my. Hoy es {1}. i18n aware templates are available via the i18n templates plugin.message(code:"my.content". 'lunes']) } 10. To get started install the i18n templates with the following command: grails install-plugin i18n-templates Then refer to the reference on the wiki which explains how to use the i18n templates. Reading Messages in Controllers and Tag Libraries Since you can invoke tags as methods from controllers it is also trivial to read messages within in a controller: def show = { def msg = message(code:"my.<g:message code="my.localized. Me llamo {0}.localized.content" args="${ ['Juan'. but note if your tag library has a different namespace then you will need to g.localized.localized. The templates are identical to the default scaffolding templates. args:['Juan'. 170 . args:['Juan'. body -> def msg = g.content=Hola.content". except that they are i18n aware using the message tag for labels. buttons etc.
1 Securing Against Attacks SQL injection Hibernate.find("from Book as b where b. and may redirect to another site or alter request parameters. However it is still possible to write bad dynamic HQL code that uses unchecked request parameters. You must also avoid the use of request parameters or data fields for determining the next URL to redirect the user to. which is the technology underlying GORM domain classes. Security Grails is no more or less secure than Java Servlets.title]) } Phishing This really a public relations issue in terms of avoiding hijacking of your branding and a declared communication policy with your customers. For example when rendering to HTML or XHTML you must call encodeAsHTML on every object to ensure that people cannot maliciously inject JavaScript or other HTML into data or tags viewed by others. attackers can imitate your login procedure using your own site. createLink. If you use a successURL parameter for example to determine where to redirect a user to after a successful login. For example doing the following is vulnerable to HQL injection attacks: def vulnerable = { def books = Book. and the tag libraries supplied by Grails all use encodeAsURL where appropriate. Grails supplies several Dynamic Encoding Methods for this purpose and if your output escaping format is not supported you can easily write your own codec. Grails provides codecs to allow you to trivially escape data when rendered as HTML. However. The default scaffolding templates HTML escape all data fields when displayed 3.11. What Grails Automatically Does Grails has a few built in safety mechanisms by default.title =?". 11. clicking it will not cause the expected behaviour. automatically escapes data when committing to database so this is not an issue. Customers need to know how to identify bonafide emails received. XSS . Java servlets (and hence Grails) are extremely secure and largely immune to common buffer overrun and malformed URL exploits due to the nature of the Java Virtual Machine underpinning the code. Web security problems typically occur due to developer naivety or mistakes. If you create your own tags that generate URLs you will need to be mindful of 171 .title + "'") } Do not do this. createLinkTo and others) all use appropriate escaping mechanisms to prevent code injection 4. and then redirect the user back to their own site once logged in. Grails link creating tags (link.find("from Book as b where b. JavaScript and URLs to prevent injection attacks here. Ticketing and page flow systems can help this and Grails' support for Spring Web Flow includes security like this by default. If you need to pass in parameters use named or positional parameters instead: def safe = { def books = Book. HTML/URL injection This is where bad data is supplied such that when it is later used to create a link in a page. form. and there is a little Grails can do to avoid common mistakes and make writing secure applications easier to write. [params.title ='" + params. All standard database access via GORM domain objects is automatically SQL escaped to prevent SQL injection attacks 2. HTML/URL injection is easily handled with the codecs supplied by Grails.cross-site scripting injection It is important that your application verifies as much as possible that incoming requests were originated from your application and not from another site. It is also important to ensure that all data values rendered into views are escaped correctly. 1. potentially allowing JS code to then exploit the logged-in account on the site.
One way to deal with that in a GSP is to encode the description property using the dynamic encode method as shown below: ${report. Not doing this is "security through obscurity" which is inevitably breached. Example of usage: <input name="comment. When a Grails application starts up the Grails framework will dynamically load codecs from the grails-app/utils/ directory. just like having a default password of "letmein" and so on. The framework will look under grails-app/utils/ for class names that end with the convention Codec.2 Encoding and Decoding Objects Grails supports the concept of dynamic encode/decode methods. A set of standard codecs are bundled with Grails. For example.decodeHTML() syntax. Standard Codecs HTMLCodec This codec perfoms HTML escaping and unescaping.encodeAsHTML()} Decoding is performed using value. Dynamic codec methods may be invoked from anywhere in a Grails application. but there are also issues relating to excessive queries for example where a link is created by an attacker to set the maximum value of a result set so that a query could exceed the memory limits of the server or slow the system down. such as the value attribute of an input field.max?. You must assume that every unprotected URL is publicly accessible one way or another. For example. Especially in the case of GORM these are easily guessable as they are typically sequential integers. For example one of the standard codecs that ship with Grails is HTMLCodec. The HTMLCodec and URLCodec classes also define a decode block so Grails will attach those with the names decodeHTML and decodeURL. Codec Classes A Grails codec class is a class that may contain an encode closure. If a codec contains an encode property assigned a block of code Grails will create a dynamic encode method and add that method to the Object class with a name representing the codec that defined the encode closure.encodeAsHTML()}"/> 172 . 11.message" value="${comment. 100) // limit to 100 results return Book. Grails also supports a simple mechanism for developers to contribute their own codecs that will be recognized at runtime.max(params. The solution here is to always sanitize request parameters before passing them to dynamic finders or other GORM query methods: def safeMax = Math. given a value "Don't you know that 2 > 1?" you wouldn't be able to show this safely within an HTML page because the > will look like it closes a tag. consider a case where a report contains a property called 'description' and that description may contain special characters that need to be escaped to be presented in an HTML document. so that values you provide can be rendered safely in an HTML page without creating any HTML tags or damaging the page layout. Therefore you must assert that the requesting user is allowed to view the object with the requested id before returning the response to the user. a decode closure or both.doing this too.description.list(max:safeMax) Guessable IDs Many applications use the last part of the URL as an "id" of some object to retrieve from GORM or elsewhere. For example. which is especially bad if you render this data within an attribute. the HTMLCodec class defines an encode block so Grails will attach that closure to the Object class with the name encodeAsHTML. Denial of service Load balancers and other appliances are more likely to be useful here.toInteger().message.
password.password. It is however.uniqueID. trivial to implement a simple authentication mechanism using either interceptors or filters. or the bytes of a string (in default system encoding).groovy: 174 . Filters allow you to apply authentication across all controllers or across a URI space.encodeAsSHA256()} SHA256BytesCodec Will use the SHA256 algorithm to digest byte arrays or lists of integers. Example of usage: Your API Key: ${user. or the bytes of a string (in default system encoding). The codec may contain a static encode block. The block should expect a single argument which will be the object that the dynamic method was invoked on.encodeAsSHA256Bytes() Custom Codecs Applications may define their own codecs and Grails will load them along with the standard codecs.Your API Key: ${user. A custom codec class must be defined in the grails-app/utils/ directory and the class name must end with Codec. For example you can create a new set of filters in a class called grails-app/conf/SecurityFilters.encodeAsPigLatin()} 11. a static decode block or both. For Example: class PigLatinCodec { static encode = { str -> // convert the string to piglatin and return the result } } With the above codec in place an application could do something like this: ${lastName.uniqueID.encodeAsSHA1()} SHA1BytesCodec Will use the SHA1 algorithm to digest byte arrays or lists of integers. Example of usage: byte[] passwordHash = params. as a byte array.encodeAsSHA1Bytes() SHA256Codec Will use the SHA256 algorithm to digest byte arrays or lists of integers.3 Authentication Although there is no current default mechanism for authentication as it is possible to implement authentication in literally thousands of different ways. as a byte array. as a lowercase hexadecimal string. or the bytes of a string (in default system encoding). Example of usage: byte[] passwordHash = params.
login) if(u) { if(u. users. extensible framework for building all sorts of authentication and authorization schemes.findByLogin(params.password) { session. The login action itself is trivial too: def login = { if(request.user && actionName != "login") { redirect(controller:"user". model:[message:"Password incorrect"]) } } else { render(view:"login". action:'*') { before = { if(!session.password == params. roles and permissions. action: 'edit') // Alternatively. only: [ 'create'. 11. etc. The plugins are modular so you can install just the functionality that you need for your application.1 Spring Security The Spring Security plugins are built on the Spring Security project which provides a flexible.class SecurityFilters { def filters = { loginCheck(controller:'*'. ACL support. etc. role(name: 'Observer') // The 'edit' action requires the 'Administrator' role.user = u redirect(action:"home") } else { render(view:"login". 11. 'update' ]) } … } 175 . role(name: 'Administrator'.4. role(name: 'Administrator'. roles etc. There is a Core plugin which supports form-based authentication. encrypted/salted passwords. several actions can be specified.action:"login") return false } } } } } Here the loginCheck filter will intercept execution before an action executed and if their is no user in the session and the action being executed is not the login action then redirect to the login action. HTTP Basic authentication. 'save'. model:[message:"User not found"]) } } } 11. and secondary dependent plugins provide alternate functionality such as OpenID authentication.4 Security Plug-ins If you need more advanced functionality beyond simple authentication such as authorization. An example below: class ExampleController extends JsecAuthBase { static accessControl = { // All actions require the 'Observer' role. See the plugin page for basic information and the user guide for detailed information. then you may want to consider using one of the available security plug-ins.2 Shiro Shiro is a Java POJO oriented security framework that provides a default domain model that models realms. With Shiro you have to extends a controller base called called JsecAuthBase in each controller you want secured and then provide an accessControl block to setup the roles.4. 'edit'.get) render(view:"login") else { def u = User.
For more information on the Shiro plugin refer to the documentation.
12. Plug-ins
Grails provides a number of extension points that allow you to extend anything from the command line interface to the runtime configuration engine. The following sections detail how to go about it.
12.1 Creating and Installing Plug-ins
Creating Plugins Creating a Grails plugin is a simple matter of running the command:
grails create-plugin [PLUGIN NAME]
This will create a plugin project for the name you specify. Say for example you run grails create-plugin example. This would create a new plugin project called example. The structure of a Grails plugin is exactly the same as a regular Grails project's directory structure, except that in the root of the plugin directory you will find a plugin Groovy file called the "plugin descriptor". Being a regular Grails project has a number of benefits in that you can immediately get going testing your plugin by running:
grails run-app
The plugin descriptor itself ends with the convention GrailsPlugin and is found in the root of the plugin project. For example:
class ExampleGrailsPlugin { def version = 0.1 … }
All plugins must have this class in the root of their directory structure to be valid. The plugin class defines the version of the plugin and optionally various hooks into plugin extension points (covered shortly). You can also provide additional information about your plugin using several special properties: title - short one sentence description of your plugin version - The version of your problem. Valid versions are for example "0.1", "0.2-SNAPSHOT", "0.1.4" etc. grailsVersion - The version of version range of Grails that the plugin supports. eg. "1.1 > *" author - plug-in author's name authorEmail - plug-in author's contact e-mail description - full multi-line description of plug-in's features documentation - URL where plug-in's documentation can be found Here is an example from Quartz Grails plugin
class QuartzGrailsPlugin { def version = "0.1" def grailsVersion = "1.1 > *" def author = "Sergey Nebolsin" def authorEmail = "email@example.com" def title = "This plugin adds Quartz job scheduling features to Grails application." def description = ''' Quartz plugin allows your Grails application to schedule jobs to be executed using a specified interval or cron expression. The underlying system uses the Quartz Enterprise Job Scheduler configured via Spring, but is made simpler by the coding by convention paradigm. ''' def documentation = "http://grails.org/Quartz+plugin" … }
Installing & Distributing Plugins To distribute a plugin you need to navigate to its root directory in a terminal window and then type:
grails package-plugin
This will create a zip file of the plugin starting with grails- then the plugin name and version. For example with the example plug-in created earlier this would be grails-example-0.1.zip. The package-plugin command will also generate plugin.xml file which contains machine-readable information about plugin's name, version, author, and so on. Once you have a plugin distribution file you can navigate to a Grails project and type:
grails install-plugin /path/to/plugin/grails-example-0.1.zip
If the plugin is hosted on a remote HTTP server you can also do:
grails install-plugin http://myserver.com/plugins/grails-example-0.1.zip
Notes on excluded Artefacts Although the create-plugin command creates certain files for you so that the plug-in can be run as a Grails application, not all of these files are included when packaging a plug-in. The following is a list of artefacts created, but not included by package-plugin: grails-app/conf/DataSource.groovy grails-app/conf/UrlMappings.groovy build.xml Everything within /web-app/WEB-INF If you need artefacts within WEB-INF it is recommended you use the _Install.groovy script (covered later), which is executed when a plug-in is installed, to provide such artefacts. In addition, although UrlMappings.groovy is excluded you are allowed to include a UrlMappings definition with a different name, such as FooUrlMappings.groovy. Specifying Plugin Locations An application can load plugins from anywhere on the file system, even if they have not been installed. Simply add the location of the (unpacked) plugin to the application's grails-app/conf/BuildConfig.groovy file:
// Useful to test plugins you are developing. grails.plugin.location.jsecurity = "/home/dilbert/dev/plugins/grails-jsecurity" // Useful for modular applications where all plugins and // applications are in the same directory. grails.plugin.location.'grails-ui' = "../grails-grails-ui"
This is particularly useful in two cases: You are developing a plugin and want to test it in a real application without packaging and installing it first. You have split an application into a set of plugins and an application, all in the same "super-project" directory.
12.2 Plugin Repositories
Distributing Plugins in the Grails Central Plugins Repository The preferred way of plugin distribution is to publish your under Grails Plugins Repository. This will make your plugin visible to the list-plugins command:
grails list-plugins
Which lists all plugins in the Grails Plugin repository and also the plugin-info command:
grails plugin-info [plugin-name]
Which outputs more information based on the meta info entered into the plug-in descriptor.
If you have created a Grails plugin and want it to be hosted in the central repository take a look at the wiki page , which details how to go about releasing your plugin in the repository.
When you have access to the Grails Plugin repository to release your plugin you simply have to execute the release-plugin command:
grails release-plugin
This will automatically commit changes to SVN, do some tagging and make your changes available via the list-plugins command. Configuring Additional Repositories The way in which you configure repositories in Grails differs between Grails versions. For version of Grails 1.2 and earlier please refer to the Grails 1.2 documentation on the subject. The following sections cover Grails 1.3 and above. Grails 1.3 and above use Ivy under the hood to resolve plugin dependencies. The mechanism for defining additional plugin repositories is largely the same as defining repositories for JAR dependencies. For example you can define a remote Maven repository that contains Grails plugins using the following syntax in grails-app/conf/BuildConfig.groovy:
repositories { mavenRepo "http://repository.codehaus.org" }
You can also define a SVN-based Grails repository (such as the one hosted at http://plugins.grails.org/) using the grailsRepo method:
repositories { grailsRepo "http://myserver/mygrailsrepo" }
There is a shortcut to setup the Grails central repository:
repositories { grailsCentral() }
The order in which plugins are resolved is based on the ordering of the repositories. So for example in this case the Grails central repository will be searched last:
Below is an example that uses an SSH resolver: def sshResolver = new SshResolver(user:"myuser".*SNAPSHOT" sshResolver.LatestTimeStrategy() sshResolver.latest. a plugin is merely a regular Grails application with a contained plug-in descriptors. Publishing to Maven Compatible Repositories In general it is recommended for Grails 1. However when installed.codehaus.setCheckmodified(true) The above example defines an artifact pattern which tells Ivy how to resolve a plugin zip file. host:"myhost.ivy. + lib + src + java + groovy + web-app + js + css 180 . For example. In addition Maven compatible repositories are not tied to SVN as Grails repositories are.myRepository setting within the grails-app/conf/BuildConfig. however you can specify any Ivy resolver to resolve plugins with.apache.com") sshResolver.org/grails/trunk/grails-test-pl You can also provide this settings in the USER_HOME/.repositories { grailsRepo "http://myserver/mygrailsrepo" grailsCentral() } All of the above examples use HTTP. In order to publish a plugin to a Maven repository you need to use the Maven publisher plugin.3 Understanding a Plug-ins Structure As as mentioned previously.plugin.groovy file: grails.changingPattern = ". For a more detailed explanation on Ivy patterns see the relevant section in the Ivy user guide.distribution.latestStrategy = new org.distribution.grails/settings. Once this is done you need to use the repository argument of the release-plugin command to specify the repository you want to release the plugin into: grails release-plugin -repository=myRepository 12.groovy file if you prefer to share the same settings across multiple projects.myRepository="https://svn. The benefits of doing so include the ability for existing tooling and repository managers to interpret the structure of a Maven repository.plugin. Publishing to Grails Compatible Repositories To publish a Grails plugin to a Grails compatible repository you specify the grails.repos.plugins.repos. the structure of a plugin differs slightly.3 and above to use standard Maven-style repositories to self host plugins. take a look at this plugin directory structure: + grails-app + controllers + domain + taglib etc. Please refer to the section of the Maven deployment user guide on the subject.addArtifactPattern("/path/to/repo/grails-[artifact]/tags/LATEST_RELEASE/grails-[artifac sshResolver.
A plugin never interferes with a project's primary source tree.0/grails-app.js" /> When you run the plugin in development mode the link to the resource will resolve to something like /js/mycode.additional services here + etc. Note that when the plugin is installed it will be loaded from where it is installed and not copied into the main application tree. the contents of the grails-app directory will go into a directory such as plugins/example-1. all static resources can go in the web-app directory.Essentially when a plugin is installed into a project.gsp then if that fails will look for the same view relative to the plug-in.js. The way it works is that Grails' view resolution mechanism will first look the view in the application it is installed into and if that fails will attempt to look for the view within the plug-in.js and Grails will deal with making sure the resources are in the right place. Dealing with static resources is slightly different. service or whatever by simply creating the relevant file within the grails-app tree. There is a special pluginContextPath variable that can be used whilst both developing the plugin and when in the plugin is installed into the application to find out what the correct path to the plugin is. + lib Adding a new Controller.additional XXX here + lib Providing Views.4 Providing Basic Artefacts Adding a new Script A plugin can add a new script simply by providing the relevant Gant script within the scripts directory of the plugin: + MyPlugin. + ExamplePlugin.additional controllers here + services <-. This is an excellent way to modularize your application through plugins. Note however that if the view uses templates that are also provided by the plugin then the following syntax may be necessary: 181 . However.additional scripts here + grails-app + controllers + services + etc.groovy + scripts <-.1/js/mycode. At runtime the pluginContextPath variable will either evaluate to an empty string or /plugins/example depending on whether the plugin is running standalone or has been installed in an application Java & Groovy code that the plugin provides within the lib and src/java and src/groovy directories will be compiled into the main project's web-app/WEB-INF/classes directory so that they are made available at runtime. Tag Library or Service A plugin can add a new controller. just like an application. 12.groovy + scripts + grails-app + controllers <-. <-. You can then link to static resources just like in an application (example below links to a javascript source): <g:resource dir="js" file="mycode. when the plugin is installed into an application the path will automatically change to something like /plugin/example-0. When developing a plugin. tag libraries. Templates and View resolution When a plug-in provides a controller it may also provide default views to be rendered. Grails will first look for a view called grails-app/views/book/list. For example given a AmazonGrailsPlugin plug-n provided controller called BookController if the action being executed is list. They will not be copied into the main source tree.
A GrailsClass represents a physical Grails resources such as a controller or a tag library.getControllerClass("ExampleController") is*Class . These include: 182 . Example application. Additionally the list of includes is extensible via the pluginExcludes property: // resources that are excluded from plugin packaging def pluginExcludes = [ "grails-app/views/error.each { println it.Returns true if the given class is of the given artefact type. when packaging a plug-in.allClasses. if you want to include demo or test resources in the plugin repository.groovy grails-app/conf/UrlMappings. get*Class . Excluded Artefacts Note that by default.isControllerClass(ExampleController.groovy is fine.name } The dynamic method conventions are as follows: *Classes . for example.groovy file is excluded to avoid naming conflicts.5 Evaluating Conventions Before moving onto looking at providing runtime configuration based on conventions you first need to understand how to evaluated those conventions from a plug-in. Essentially every plugin has an implicit application variable which is an instance of the GrailsApplication interface. which contains the name of the plugin where the template resides.each { println it.Retrieves a named class for a particular artefact.<g:render template="fooTemplate" plugin="amazon"/> Note the usage of the plugin attribute.class) The GrailsClass interface itself provides a number of useful methods that allow you to further evaluate and work with the conventions. For example to get all GrailsClass instances you can do: application. Example application.gsp" ] This is useful. In addition. the default UrlMappings. For example a file called grails-app/conf/BlogUrlMappings. however you are free to add a UrlMappings definition under a different name which will be included.groovy Gant script to install these artefacts into the target project's directory tree. 12. but not include them in the final distribution.Retrieves all the classes for a particular artefact name. If this is not specified then Grails will look for the template relative to the application. The GrailsApplication interface provides methods to evaluate the conventions within the project and internally stores references to all classes within a GrailsApplication using the GrailsClass interface.controllerClasses.name } There are a few "magic" properties that the GrailsApplication instance possesses that allow you to narrow the type of artefact you are interested in.controllerClasses. For example if you only want to controllers you can do: application.groovy Everything under web-app/WEB-INF If your plug-in does require files under the web-app/WEB-INF directory it is recommended that you modify the plug-in's scripts/_Install. Example application. Grails will excludes the following files from the packaged plug-in: grails-app/conf/DataSource.
e.Returns the package name For a full reference refer to the javadoc API. These are events triggered during execution of Grails target and plugin scripts. todir:"${basedir}/grails-app/conf") // To access Grails home you can use following code: // Ant.7 Hooking into Runtime Configuration Grails provides a number of hooks to leverage the different parts of the system and perform runtime configuration by convention. you can hook into status update output (i. 'lastName' becomes 'Last Name') getPackageName . 12. you can hook in Grails runtime configuration by providing a property called doWithSpring which is assigned a block of code. As an example the below _Install.Creates a new instance of this class. An addition to the standard Gant variables is the pluginBasedir variable which points at the plugin installation basedir.Returns the full name of the class in the application with the trailing convention part and with the package name getPropertyName . Hooking into the Grails Spring configuration First.Returns true if the class has the specified property newInstance .Returns the name of the property in natural terms (eg. Refer the documentation on Hooking into Events for further information. This is achieved via two specially named scripts under scripts directory of the plugin _Install. "Server running") and the creation of files or artefacts.6 Hooking into Build Events Post-Install Configuration and Participating in Upgrades Grails plug-ins can do post-install configuration and participate in application upgrade process (the upgrade command).groovy".groovy script will create a new directory type under the grails-app directory and install a configuration template: Ant.Returns the logical name of the class in the application without the trailing convention part if applicable getShortName .Returns the short name of the class without package prefix getFullName . _Install.Returns the logical property name of the class in the application without the trailing convention part if applicable getNaturalName .mkdir(dir:"${basedir}/grails-app/jobs") Ant. "Tests passed". For example.property(environment:"env") // grailsHome = Ant.getPropertyValue . For example the following snippet is from one of the core Grails plugins that provides i18n support: 183 . getName .antProject.groovy is executed after the plugin has been installed and _Upgrade. A plug-in merely has to provide an _Events.Gets the initial value of the given property on the class hasProperty .Returns the name of the class as a property name getLogicalPropertyName .groovy.groovy is executed each time the user upgrades his application with upgrade command.copy(file:"${pluginBasedir}/src/samples/SamplePluginConfiguration.GRAILS_HOME" Scripting events It is also possible to hook into command line scripting events through plug-ins.groovy and _Upgrade."env. These scripts are normal Gant scripts so you can use the full power of Gant.properties.groovy script to listen to the required events. 12.
xml Generation Grails generates the WEB-INF/web. constructors etc.xml as a XmlSlurper GPathResult. class SimplePlugin { def name="simple" def version = 1.import org.web.servlet.i18n. Participating in web. For Grails managed classes like controllers.springframework. using the ExpandoMetaClass mechanism by accessing each controller's MetaClass: 184 .springframework. class I18nGrailsPlugin { def version = 0. import org. New methods can only be added within a doWithDynamicMethods closure of a plugin. Consider the below example from the ControllersPlugin: def doWithWebDescriptor = { webXml -> def mappingElement = webXml. Essentially a plugin can provide a doWithWebDescriptor property that is assigned a block of code that gets passed the web.1 def doWithApplicationContext = { appCtx -> SessionFactory sf = appCtx.web. In this case you can define a doWithApplicationContext closure property. import org.getBean("sessionFactory") // do something here with session factory } } 12.context.ReloadableResourceBundleMessageSource. tag libraries and so forth you can add methods. they can participate in the generation of the file. It using the Spring Bean Builder syntax to do so.size()-1] lastMapping + { 'servlet-mapping' { 'servlet-name'("grails") 'url-pattern'("*.dispatch") } } } Here the plugin goes through gets a reference to the last <servlet-mapping> element and appends Grails' servlet to the end of it using XmlSlurper's ability to programmatically modify XML using closures and blocks.xml file at load time. Doing Post Initialisation Configuration Sometimes it is useful to be able do some runtime configuration after the Spring ApplicationContext has been built.springframework.servlet.CookieLocaleResolver.1 def doWithSpring = { messageSource(ReloadableResourceBundleMessageSource) { basename = "WEB-INF/grails-app/i18n/messages" } localeChangeInterceptor(LocaleChangeInterceptor) { paramName = "lang" } localeResolver(CookieLocaleResolver) } } This plugin sets up the Grails messageSource bean and a couple of other beans to manage Locale resolution and switching.i18n.'servlet-mapping' def lastMapping = mappingElement[mappingElement.LocaleChangeInterceptor.8 Adding Dynamic Methods at Runtime The Basics Grails plugins allow you to register dynamic methods with any Grails managed or other class at runtime. and although plugins cannot change this file directly.support.
each { controllerClass -> controllerClass.orm.metaClass.swapCase() } } In this example we add a new method swapCase to java.load = { Long id-> def sf = applicationContext.metaClass. id) } } } } Also because of the autowiring and dependency injection capability of the Spring container you can implement more powerful dynamic constructors that use the application context to wire dependencies into your object at runtime: class MyConstructorPlugin { def doWithDynamicMethods = { applicationContext -> application.toLowerCase(it as char) : Character.isUpperCase(it as char) ? Character. if you know before hand the class you wish the add a method to you can simple reference that classes metaClass property: class ExamplePlugin { def doWithDynamicMethods = { applicationContext -> String.toUpperCase(it as char)) } sb.lang.static.hibernate3.String directly by accessing its metaClass.name) } } } } Here we actually replace the default constructor with one that looks up prototyped Spring beans instead! 12.swapCase = {-> def sb = new StringBuffer() delegate.metaClass.sessionFactory def template = new HibernateTemplate(sf) template.each { sb << (Character. This is useful as it allows you to interact with objects within it.controllerClasses.each { domainClass -> domainClass. Alternatively.9 Participating in Auto Reload Events 185 .springframework.toString() } assert "UpAndDown" == "uPaNDdOWN".each { domainClass -> domainClass. For example if you where implementing a method to interact with Hibernate you could use the SessionFactory instance in combination with a HibernateTemplate: import org.getBean(domainClass.domainClasses.class ExamplePlugin { def doWithDynamicMethods = { applicationContext -> application.constructor = {-> return applicationContext.domainClasses.HibernateTemplate class ExampleHibernatePlugin { def doWithDynamicMethods = { applicationContext -> application.metaClass.load(delegate. Interacting with the ApplicationContext The doWithDynamicMethods closure gets passed the Spring ApplicationContext instance.myNewMethod = {-> println "hello world" } } } } In this case we use the implicit application object to get a reference to all of the controller classes' MetaClass instances and then add a new method called myNewMethod to each controller.
If the watched resources is a Groovy file.registerBeanDefinition(serviceName.addServiceClass(event. unless you reload the controllers too.getClazz()) { bean -> bean. you can specify which plugins another plugin "influences". problems will occur when you try to auto-wire the reloaded service into an older controller Class.source) def serviceName = "${serviceClass. sometimes one plugin needs to "influence" another plugin. consider the below simplified snippet from the ServicesPlugin that Grails comes with: class ServicesGrailsPlugin { … def watchedResources = "file:. beans. When a service is reloaded. The event object defines a number of useful properties: event.plugin .The plugin object that manages the resource (Usually this) event. For example.source . In the "Services" example above. This is how Grails implements advanced reloading of application state at runtime. It is also possible for a plugin to observe all loaded plugins by using a wildcard: 186 . a new services bean is re-registered with the ApplicationContext when one of the service classes changes. it will reload itself and then reload all influenced plugins.ctx .ctx.The GrailsApplication instance From these objects you can evaluate the conventions and then apply the appropriate changes to the ApplicationContext and so forth based on the conventions. See this snippet from the ServicesGrailsPlugin: def influences = ['controllers'] Observing other plugins If there is a particular plugin that you would like to observe for changes but not necessary watch the resources that it monitors you can use the "observe" property: def observe = ["controllers"] In this case when a controller is changed you will also receive the event chained from the controllers plugin./grails-app/services/*Service. when it is changed it will automatically be reloaded and passed into the onChange closure inside the event object.The Spring ApplicationContext instance event. To get round this. What this means is that when one plugin detects a change. Take for example the Services & Controllers plugins. etc.The source of the event which is either the reloaded class or a Spring Resource event.groovy" … def onChange = { event -> if(event.ctx) { event.autowire = true } } if(event.source) { def serviceClass = application. Influencing Other Plugins As well as being able to react to changes that occur when a plugin changes.Monitoring Resources for Changes Often it is valuable to monitor resources for changes and then reload those changes when they occur.application .getBeanDefinition(serviceName)) } } } } Firstly it defines a set of watchedResources as either a String or a List of strings that contain either the references or patterns of the resources to watch.propertyName}" def beans = beans { "$serviceName"(serviceClass.
For example. The dependsOn property also supports a mini expression language for specifying version ranges.10 Understanding Plug-in Load Order Controlling Plug-in Dependencies Plug-ins often depend on the presence of other plugins and can also adapt depending on the presence of others. the i18n plugin and the core plugin. The first is called dependsOn. otherwise it will just be loaded.0.1"] def dependsOn = [foo:"1. To cover this. then the plugin will not load. The domainClass plugin.1-BETA2 Controlling Load Order Using dependsOn establishes a "hard" dependency in that if the dependency is not resolved. take a look at this snippet from the Grails Hibernate plugin: class HibernateGrailsPlugin { def version = 1. so for example the expression "1. If all dependencies do not load.3-SNAPSHOT 1.1" would match any of the following versions: 1. i18n:1.0.0. domainClass:1.0 > 1.0 1.0"] def dependsOn = [foo:"1.0 > *"] When the wildcard * character is used it denotes "any" version.def observe = ["*"] The Logging plugin does exactly this so that it can add the log property back to any artefact that changes while the application is running. a plugin can define two properties.1 1. the plugin will give up and won't load.0.1 1. Essentially the dependencies will be loaded first and then the Hibernate plugin. It is possible though to have a "weaker" dependency using the loadAfter property: def loadAfter = ['controllers'] Here the plugin will be loaded after the controllers plugin if it exists. core: 1.0] } As the above example demonstrates the Hibernate plugin is dependent on the presence of 4 plugins: The dataSource plugin. The plugin can then adapt to the presence of the other plugin. 12.0 def dependsOn = [dataSource:1. The expression syntax also excludes any suffixes such as -BETA. for example the Hibernate plugin has this code in the doWithSpring closure: 187 .0 > 1. A few examples of the syntax can be seen below: def dependsOn = [foo:"* > 1.0. -ALPHA etc.
188 . The manager variable is an instance of the GrailsPluginManager interface and it provides methods to interact with other plugins and the GrailsPluginManager itself from any plugin.hasGrailsPlugin("controllers")) { openSessionInViewInterceptor(OpenSessionInViewInterceptor) { flushMode = HibernateAccessor.FLUSH_MANUAL sessionFactory = sessionFactory } grailsUrlHandlerMapping.if(manager?.interceptors << openSessionInViewInterceptor } Here the Hibernate plugin will only register an OpenSessionInViewInterceptor if the controllers plugin has been loaded.
POST and DELETE. POST and DELETE map to unique actions within the controller as outlined by the table below: Method Action GET show PUT POST update save DELETE delete You can alter how HTTP methods by using the capability of URL Mappings to map to HTTP methods: "/product/$id"(controller:"product"){ action = [GET:"show". DELETE:"delete". For example GET for retrieving data. In this sense REST fits quite well with CRUD. PUT:"update". in this case Grails will not provide automatic XML or JSON marshaling for you unless you specify the parseRequest argument in the URL mapping: "/product/$id"(controller:"product". PUT:"update". DELETE:"delete". Writing a REST client that then sends a specific HTTP method is then trivial (example in Groovy's HTTPBuilder module): 189 . 13. POST for updating and so on. POST:"save"] } However. PUT. URL patterns The first step to implementing REST with Grails is to provide RESTful URL mappings: static mappings = { "/product/$id?"(resource:"product") } What this does is map the URI /product onto a ProductController. parseRequest:true){ action = [GET:"show". Web Services Web services are all about providing a web API onto your web application and are typically implemented in either SOAP or REST.1 REST REST is not really a technology in itself. unlike the resource argument used previously. POST:"save"] } HTTP Methods In the previous section you saw how you can easily define URL mappings that map specific HTTP methods onto specific controller actions. REST is extremely simple and just involves using plain XML or JSON as a communication medium. PUT. Each HTTP method maps to an action. PUT for creating data. Each HTTP method such as GET.13. but more an architectural pattern. combined with URL patterns that are "representational" of the underlying system and HTTP methods such as GET.
import groovyx.net.0" encoding="ISO-8859-1"?> <product> <name>MacBook</name> <vendor id="12"> <name>Apple</name> </vender> </product> You can read this XML packet using the same techniques described in the Data Binding section via the params object: 190 . } Here what we do is if there is an id we search for the Product by name and return it otherwise we return all Products. Given an incoming XML packet of: <?xml version="1. issuing a request with a method other than GET or POST from a regular browser is not possible without some help from Grails.ContentType. When defining a form you can specify an alternative method such as DELETE: <g:form controller="book" method="DELETE"> .* import static groovyx.books.path = '/book/list' response. JSON) { url..findByName(params. XML Marshalling . json -> json.id) render p as XML } else { def all = Product.Updating To support updates such as PUT and POST you can use the params object which Grails enhances with the ability to read an incoming XML packet. XML Marshaling .* class ProductController { def show = { if(params. which will be used as the request's HTTP method.http.id && Product. </g:form> Grails will send a hidden parameter called _method.list() render all as XML } } .Reading The controller implementation itself can use Grails' XML marshaling support to implement the GET method: import grails.each { book -> println book.id)) { def p = Product. Another alternative for changing the method for non-browser clients is to use the X-HTTP-Method-Override to specify the alternative method name.request(Method.converters.exists(params.JSON def http = new HTTPBuilder("http://localhost:8080/amazon") http.title } } } However.net.GET..success = {resp. This way if we go to /products we get all products.http. otherwise if we go to /product/MacBook we only get a MacBook.
There is however a Feeds plug-in available for Grails that provides a RSS and 191 . The below example is taken from the XFire plugin: class BookService { static expose=['xfire'] Book[] getBooks(){ Book. The exact same technique can be used with a JSON request too. If you require different responses to different clients (REST. HTML etc.errors } } In this example by indexing into the params object using the key 'product' we can automatically create and bind the XML using the constructor of the Product class.0.2 SOAP There are several plugins that add SOAP support to Grails depending on your preferred approach.def save = { def p = new Product(params['product']) if(p.save()) { render p as XML } else { render p.1:8080/your_grails_app/services/book?wsdl For more information on the XFire plug-in refer the documentation on the wiki. whilst if you want to generate a SOAP API from Grails services there are several plugins that do this including: XFire plugin which uses the XFire SOAP stack CXF plugin which uses the CXF SOAP stack Axis2 plugin which uses Axis2 Metro plugin which uses the Metro framework (and can also be used for Contract First) Most of the SOAP integrations integrate with Grails services via the exposes static property. otherwise an error message is produced using Grails' validation capabilities in the form: <error> <message>The property 'title' of class 'Person' must be specified</message> </error> 13. An interesting aspect of the line: def p = new Product(params['product']) Is that it requires no code changes to deal with a form submission that submits form data than it does to deal with an XML request.3 RSS and Atom No direct support is provided for RSS or Atom within Grails. You could construct RSS or ATOM feeds with the render method's XML capability.0.) you can use content negotation The Product object is then saved and rendered as XML. 13.list() as Book[] } } The WSDL can then be accessed at the location: http://127. For Contract First SOAP services there is a Spring WS plugin.
An example of its usage can be seen below: def feed = { render(feedType:"rss".list().server/article/${it.Atom builder using the popular ROME library.0") { title = "My test feed" link = "http://your.id}" it.content // return the content } } } } 192 .each() { entry(it.test. feedVersion:"2.test.server/yourController/feed" Article.title) { link = "http://your.
it is superbly designed and architected and was.xml can also reference Grails classes by convention. in this case named myBean.MyBeanImpl"></bean> Once configured the bean. Each plug-in may configure Spring beans that are registered with the ApplicationContext.2 Configuring Additional Beans Using XML Beans can be configured using the grails-app/conf/spring/resources. This file is typical Spring XML file and the Spring documentation has an excellent reference on how to go about configuration Spring beans. tag libraries. can be auto-wired into most Grails types including controllers.xml.Grails uses Spring's transaction management in GORM In other words Grails has Spring embedded running all the way through it. services and so on: class ExampleController { def myBean } Referencing Existing Beans Beans declared in resources. 14. For example: 193 . For example if you need a reference to a service such as BookService in your bean you use the property name representation of the class name.14. Grails leverages Spring MVC in the following areas: Basic controller logic . As a trivial example you can configure a bean with the following syntax: <bean id="myBean" class="my. In the case of BookService this would be bookService.xml file of your Grails application. Spring MVC is the Spring framework's built-in MVC web application framework.1 The Underpinnings of Grails Grails is actually a Spring MVC application in disguise. The basics of it are as follows.Grails subclasses Spring's DispatcherServlet and uses it to delegate onto Grails controllers Data Binding and Validation . Grails and Spring This section is for advanced users and those who are interested in how Grails integrates with and builds on the Spring Framework This section is also useful for plug-in developers considering doing runtime configuration Grails. for Grails. Grails constructs a parent ApplicationContext from the web-app/WEB-INF/applicationContext. 14. the perfect framework to build another framework on top of.Grails' entire runtime convention based system is wired together by a Spring ApplicationContext Transactions . For a reference as to which beans are configured refer to the reference guide which describes each of the Grails plug-ins and which beans they configure.Grails' validation and data binding capabilities are built on those provided by Spring Runtime configuration . Although Spring MVC suffers from the same difficulties as frameworks like Struts in terms of its ease of use. The Grails ApplicationContext Spring developers are often keen to understand how the Grails ApplicationContext instance is constructed. Using this ApplicationContext as a parent Grails' analyses the conventions with the GrailsApplication instance and constructs a child ApplicationContext that is used as the root ApplicationContext of the web application Configured Spring Beans Most of Grails' configuration happens at runtime. This ApplicationContext sets up the GrailsApplication instance and the GrailsPluginManager.company.
company.company. } } Since much of Grails configuration is done at runtime by convention many of the beans are not declared anywhere.company. For example if you need a reference to the Grails DataSource you could do: <bean id="myBean" class="my.MyBeanImpl"> <property name="bookService" ref="bookService" /> <property name="dataSource" ref="dataSource" /> </bean> Or if you need the Hibernate SessionFactory this will work: <bean id="myBean" class="my. public void setBookService(BookService theBookService) { this.<bean id="myBean" class="my.bookService = theBookService. class MyBeanImpl { private BookService bookService. Using the Spring DSL If you want to use the Spring DSL that Grails provides then you need to create a grails-app/conf/spring/resources.groovy file and define a property called beans that is assigned a block: beans = { // beans here } The same configuration for the XML example could be represented as: 194 . but can still be referenced inside your Spring configuration.MyBeanImpl"> <property name="bookService" ref="bookService" /> </bean> The bean itself would of course need a public setter.MyBeanImpl"> <property name="bookService" ref="bookService" /> <property name="sessionFactory" ref="sessionFactory" /> </bean> For a full reference of the available beans see the Plug-in reference in the reference guide.company. which in Groovy is defined like this: package my.company class MyBeanImpl { BookService bookService } or in Java like this: package my.
MyBeanImpl) { bookService = ref("bookService") } } The main advantage of this way is that you can now mix logic in within your bean definitions.hbm2ddl. import org.company. Spring's regular way of configuration (via XML) is essentially static and very difficult to modify and configure at runtime other than programmatic XML creation which is both error prone and verbose. In addition.jdbcDriver" url = "jdbc:hsqldb:mem:grailsDB" username = "sa" password = "" } sessionFactory(ConfigurableLocalSessionFactoryBean) { dataSource = dataSource hibernateProperties = [ "hibernate.groovy file you don't need to create a new instance of BeanBuilder.beans { dataSource(BasicDataSource) { driverClassName = "org.context.MockImpl) { bookService = ref("bookService") } break } } 14.environment) { case "production": myBean(my.apache.mock.spring.BasicDataSource import org.* beans = { switch(GrailsUtil.dbcp.ApplicationContext.hsqldb.codehaus.3 Runtime Spring with the Beans DSL This Bean builder in Grails aims to provide a simplified way of wiring together dependencies that uses Spring at its core.commons. "hibernate.ConfigurableLocalSessionFactoryBean.util.beans = { myBean(my.hibernate. The basics are as follows: import org. for example based on the environment: import grails.springframework. Grails' BeanBuilder changes all that by making it possible to programmatically wire together components at runtime thus allowing you to adapt the logic based on system properties or environment variables. def bb = new grails. development and production environments) The BeanBuilder class Grails provides a grails.createApplicationContext() Within plug-ins and the grails-app/conf/spring/resources.auto":"create-drop". This enables the code to adapt to its environment and avoids unnecessary duplication of code (having different Spring configs for test. Instead the DSL is implicitly available inside the doWithSpring and beans blocks respectively.MyBeanImpl) { bookService = ref("bookService") } break case "development": myBean(my.BeanBuilder() bb.spring.groovy.orm.show_sql":true ] } } ApplicationContext appContext = bb.company.grails.BeanBuilder class that uses dynamic Groovy to construct bean definitions. 195 .company.
as seen in the following code: sessionFactory(ConfigurableLocalSessionFactoryBean) { bean -> bean.BasicDataSource) { driverClassName = "org. whilst the last argument is a block.loadBeans("classpath:*SpringBeans. [autowire bean.groovy and parse them into bean definitions.scope = 'request' // Sets the scope of the bean. "hibernate.jdbcDriver" url = "jdbc:hsqldb:mem:grailsDB" username = "sa" password = "" } } Loading Bean Definitions from the File System You can use the BeanBuilder class to load external Groovy scripts that define beans using the same path matching syntax defined here. Using BeanBuilder with Spring MVC If you want to take advantage of BeanBuilder in a regular Spring MVC application you need to make sure the grails-spring-<version>. Certain special properties related to bean management can also be set by the builder.auto":"create-drop". [init-method] bean.spring.commons. [scope] dataSource = dataSource hibernateProperties = [ "hibernate.groovy file that does the rest: beans { dataSource(org.jar file is in your classpath.createApplicationContext() Here the BeanBuilder will load all Groovy files on the classpath ending with SpringBeans. An example script can be seen below: 196 .initMethod = 'init' // Sets the initialisation method to 'init'.show_sql":true ] } The strings in square brackets are the names of the equivalent bean attributes in Spring's XML definition.xml file: <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/applicationContext.groovy.dbcp. Essentially. each method call (in this case dataSource and sessionFactory calls) map to the name of the bean in Spring.autowire = 'byName' // Autowiring behaviour. The other option is 'byType'.The above example shows how you would configure Hibernate with an appropriate data source with the BeanBuilder class. Once that is done you can need to set the following <context-param> values in your /WEB-INF/web.groovy") def applicationContext = bb.commons. [destroy-method] bean.apache.GrailsWebApplicationContext</param-value </context-param> With that done you can then create a /WEB-INF/applicationContext.codehaus.grails. The first argument to the method is the bean's class.destroyMethod = 'destroy' // Sets the destruction method to 'destroy'.hbm2ddl.hsqldb. This can be seen in the example above with the way the sessionFactory bean resolves the dataSource reference.groovy</param-value> </context-param> <context-param> <param-name>contextClass</param-name> <param-value>org. Example: def bb = new BeanBuilder() bb. Within the body of the block you can set properties on the bean using standard Groovy syntax Bean references are resolved automatically be using the name of the bean.
beans { exampleBean(MyExampleBean) { bean -> bean.beans { def example = exampleBean(MyExampleBean) { someProperty = [1.auto":"create-drop".factoryMethod = "getInstance" bean.factoryMethod = "getInstance" } Using Factory beans Spring defines the concept of factory beans and often a bean is created not from a class.jdbcDriver" url = "jdbc:hsqldb:mem:grailsDB" username = "sa" password = "" } sessionFactory(ConfigurableLocalSessionFactoryBean) { dataSource = dataSource hibernateProperties = [ "hibernate.binding = binding bb.3] } example. "firstArgument".3] } } As an alternative you can also use the return value of the bean defining method to configure the bean: bb.foo = "bar" def bb = new BeanBuilder() bb.4 The BeanBuilder DSL Explained Using Constructor Arguments Constructor arguments can be defined using parameters to each method that reside between the class of the bean and the last closure: bb.2. 2) { someProperty = [1.hbm2ddl. which you can use to configure factory methods and invoke any method on the AbstractBeanDefinition class: bb.show_sql":true ] } } Adding Variables to the Binding (Context) If you're loading beans from a script you can set the binding to use by creating a Groovy Binding object: def binding = new Binding() binding. In this case the bean has no class and instead you must pass the name of the factory bean to the bean: 197 .2.hsqldb. but from one of these factories.createApplicationContext() 14. "hibernate.singleton = false someProperty = [1.3] } } Configuring the BeanDefinition (Using factory methods) The first argument to the closure is a reference to the bean configuration instance.beans { dataSource(BasicDataSource) { driverClassName = "org.beans { exampleBean(MyExampleBean.groovy") def ctx = bb.2.loadBeans("classpath:*SpringBeans.
2.3] } anotherBean(AnotherBean) { example = ref("${beanName}Bean") } } Here the example property of AnotherBean is set using a runtime reference to the exampleBean.beans { "${beanName}Bean"(MyExampleBean) { someProperty = [1. because sometimes bean names are not known until runtime you may need to reference them by name when wiring together other beans.beans { "${beanName}Bean"(MyExampleBean) { someProperty = [1. Another common task is provide the name of the factory method to call on the factory bean.bb. Creating Bean References at Runtime Sometimes you don't know the name of the bean to be created until runtime. In this case using the ref method: def beanName = "example" bb.beans { myFactory(ExampleFactoryBean) { someProperty = [1.2. In this case you can use a string interpolation to invoke a bean defining method dynamically: def beanName = "example" bb.3] } myBean(myFactory) { name = "blah" } } Note in the example above instead of a class we pass a reference to the myFactory bean into the bean defining method.2. The ref method can also be used to refer to beans from a parent ApplicationContext that is provided in the constructor of the BeanBuilder: 198 . Furthermore.3] } } In this case the beanName variable defined earlier is used when invoking a bean defining method.3] } myBean(myFactory:"getInstance") { name = "blah" } } Here the getInstance method on the ExampleFactoryBean bean will be called in order to create the myBean bean.2. This can be done using Groovy's named parameter syntax: bb.beans { myFactory(ExampleFactoryBean) { someProperty = [1.
Alternatively if you have a factory bean you can ommit the type and just use passed bean definition instead to setup the factory: bb.beans { personFactory(PersonFactory.. height:"1.class) { name = "marge" husband = { bean -> bean.8m"] } children = [bart.8m"] } children = [bart..beans { marge(Person. true) } } Here the second parameter true specifies that the reference will look for the bean in the parent context.factoryBean = "personFactory" bean. Using Anonymous (Inner) Beans You can use anonymous inner beans by setting a property of the bean to a block that takes an argument that is the bean type: bb.class) { name = "marge" husband = { Person p -> name = "homer" age = 45 props = [overweight:true. lisa] } } Abstract Beans and Parent Bean Definitions To create an abstract bean definition define a bean that takes no class: 199 . height:"1.class) marge(Person. lisa] } bart(Person) { name = "Bart" age = 11 } lisa(Person) { name = "Lisa" age = 9 } } In the above example we set the marge bean's husband property to a block that creates an inner bean reference.ApplicationContext parent = .factoryMethod = "newInstance" name = "homer" age = 45 props = [overweight:true.// der bb = new BeanBuilder(parent) bb.beans { anotherBean(AnotherBean) { example = ref("${beanName}Bean".
'abstract' = true leader = "Lancelot" } quest(HolyGrailQuest) knights("Camelot") { bean -> bean. With BeanBuilder you can use any Spring namespace by first declaring it: xmlns context:"http://www.spring.0.parent = abstractBean quest = quest } } When using a parent bean you must set the parent property of the bean before setting any other properties on the bean! If you want an abstract bean that has a class you can do it this way: def bb = new grails. Using Spring Namespaces Since Spring 2. "Camelot") { bean -> bean.beans { abstractBean { leader = "Lancelot" } … } Here we define an abstract bean that sets that has a leader property with the value of "Lancelot". but inherits the class from the parent bean. users of Spring have been granted easier access to key features via XML namespaces.start() } } def bb = new grails.parent = abstractBean quest = quest } } In the above example we create an abstract bean of type KnightOfTheRoundTable and use the bean argument to set it to abstract.BeanBuilder() bb.org/schema/context" 200 .beans { abstractBean(KnightOfTheRoundTable) { bean -> bean.BeanBuilder() bb.name = n } HolyGrailQuest quest def embarkOnQuest() { quest. Now to use the abstract bean set it as the parent of the child bean: bb.beans { … quest(HolyGrailQuest) knights(KnightOfTheRoundTable.class HolyGrailQuest { def start() { println "lets begin" } } class KnightOfTheRoundTable { String name String leader KnightOfTheRoundTable(String n) { this.spring. Later we define a knights bean that has no class.springframework.
'jndi-name':"java:comp/env/myDataSource") The example above will create a Spring bean with the identifier of dataSource by performing a JNDI lookup on the given JNDI name.domain" ) You can do some useful things with Spring namespaces..groovy (or an externalized config): database.springframework.5 Property Placeholder Configuration Grails supports the notion of property placeholder configuration through an extended version of Spring's PropertyPlaceholderConfigurer.xml.springframework.'jndi-lookup'(id:"dataSource".ref:"birthdayCardSenderAspect" ) { after method:"onBirthday".org/schema/jee" jee.dbname="mysql:mydb" You can then specify placeholders in resources. which is typically useful when used in combination with externalized configuration. pointcut: "execution(void .} syntax: 201 .Driver" database. Settings defined in either ConfigSlurper scripts of Java properties files can be used as placeholder values for Spring configuration in grails-app/conf/spring/resources. For example given the following two classes: class Person { int age.jdbc.'component-scan'( 'base-package' :"my.And then invoking a method that matches the names of the Spring namespace tag and its associated attributes: context.Person. For example given the following entries in grails-app/conf/Config. such as looking up a JNDI resource: xmlns jee:"http://www. void birthday() { ++age.company.org/schema/aop" fred(Person) { name = "Fred" age = 45 } birthdayCardSenderAspect(BirthdayCardSender) aop { config("proxy-target-class":true) { aspect( id:"sendBirthdayCard".xml as follows using the familiar ${.mysql.birthday()) and this(person } } } 14. With Spring namespaces you also get full access to all of the powerful AOP support in Spring from BeanBuilder.driver="com. } } class BirthdayCardSender { List peopleSentCards = [] void onBirthday(Person person) { peopleSentCards << person } } You can define an AOP aspect that uses a pointcut to detect whenever the birthday() method is called: xmlns aop:"http://www.. String name.
webServiceURL=http://www.[property name] = [value] The same configuration in a Java properties file would be: beans. This is often useful when used in combination with externalized configuration.6 Property Override Configuration Grails supports setting of bean properties via configuration.driver}</value></property> <property name="url"><value>jdbc:${database.DriverManagerDataSource"> <property name="driverClassName"><value>${database.jdbc.com" } } The general format is: [bean name].datasource.dbname}</value></property> </bean> 14.amazon.com 202 .<bean id="dataSource" class="org. Essentially you define a beans block with the names of beans and their values: beans { bookService { webServiceURL = "http://www.springframework.amazon.bookService.
To create an annotated domain class.Book" /> </session-factory> </hibernate-configuration> By default the hibernate.0 Annotations support.cfg.0. } public void setId(Long id) { this.groovy: 203 .xml file as follows: <!DOCTYPE hibernate-configuration SYSTEM "http://hibernate. } } Once that is done you need to register the class with the Hibernate sessionFactory. private String title.0 spec (for more info on this see the Hibernate Annotations Docs): package com. } public void setDescription(String description) { this.sourceforge.xml file is located in the grails-app/conf/hibernate directory. You can do this manually or by running the create-hibernate-cfg-xml script. } public String getTitle() { return title. private String description. } public String getDescription() { return description. Additionally.15. To do this create a hibernate. @Entity public class Book { private Long id.dtd"> <hibernate-configuration> <session-factory> <mapping package="com. to do you need to add entries to the grails-app/conf/hibernate/hibernate.net/hibernate-configuration-3.books" /> <mapping class="com. create a new class in src/java and use the annotations defined as part of the EJB 3. you will still be able to call all of the dynamic persistent and query methods allowed in GORM! 15. private Date date. @Id @GeneratedValue public Long getId() { return id. If you wish to change this you can do so by specifying an alternative location in grails-app/conf/DataSource.1 Mapping with Hibernate Annotations Grails also supports creating domain classes mapped with Hibernate's Java 5. For more info on how to do this read the documentation on mapping at the Hibernate Website This will allow you to map Grails domain classes onto a wider range of legacy systems and have more flexibility in the creation of your database schema.books.cfg.cfg. } public void setTitle(String title) { this.id = id. Grails and Hibernate If GORM (Grails Object Relational Mapping) is not flexible enough for your liking you can alternatively write some or all of your domain classes in Java or re-use an existing domain model that has been mapped using Hibernate.books.description = description.title = title.xml file in the grails-app/conf/hibernate directory of your project and add the corresponding HBM mapping xml files for your domain classes.
"file:/path/to/two/hibernate.cfg.Another great article about using Grails with EJB3-style annotated domain models 204 .An excellent article about using Grails with Hibernate XML Grails + EJB3 Domain Models .location = ["file:/path/to/one/hibernate.xml"] } When Grails loads it will register the necessary dynamic methods with the class.xml".2 Further Reading Grails committer.location = "file:/path/to/my/hibernate.hibernate { config. took the time to write many useful articles about using Grails with custom Hibernate mappings including: Hoisting Grails to Your Legacy DB . 15.cfg.xml" } Or even a list of locations: hibernate { config. Jason Rudolph. To see what else you can do with a Hibernate domain class see the section on Scaffolding.cfg.
Scaffolding Scaffolding allows you to auto-generate a whole application for a given domain class including: The necessary views Controller actions for create/read/update/delete (CRUD) operations Enabling Scaffolding The simplest way to get started with scaffolding is to enable scaffolding via the scaffold property. you need to set the scaffold property on a controller to true: class BookController { def scaffold = true } The above works because the BookController follows the same naming convention as the Book domain class. For example.save() // redirect to a scaffolded action redirect(action:show) } } You can also override the scaffolded actions with your own actions if necessary: 205 .get( params["id"] ) b.16. The following actions are dynamically implemented by default by the runtime scaffolding mechanism: list show edit delete create save update As well as this a CRUD interface will be generated. in the below example. or code generation to achieve this so you can add your own actions to the scaffolded controller that interact with the scaffolded actions. To access the interface in the above example simply go to http://localhost:8080/app/book If you prefer to keep your domain model in Java and mapped with Hibernate you can still use scaffolding.author = Author. changeAuthor redirects to the show action which doesn't actually exist physically: class BookController { def scaffold = Book def changeAuthor = { def b = Book. Dynamic Scaffolding Note that when using the scaffold property Grails does not use code templates. For the Book domain class.get( params["author. if we wanted to scaffold a specific domain class you can reference the class directly in the scaffold property: def scaffold = Author With that done if you run this grails application the necessary actions and views will be auto-generated at runtime.id"] ) b. simply import the necessary class and set the scaffold property to it.
For example you can change the order that fields appear in the views simply by re-ordering the constraints in the builder: def constraints = { title() releaseDate() } You can also get the generator to generate lists instead of text inputs if you use the inList constraint: def constraints = { title() category(inList:["Fiction". "authors": Author.30) } Generating Controllers & Views The above scaffolding features are useful but in real world situations its likely that you will want to customize the logic and views...list(). Customizing the Generated Views The views that Grails generates have some form of intelligence in that they adapt to the Validation constraints.list() ] } } All of this is what is known as "dynamic scaffolding" where the CRUD interface is generated dynamically at runtime. "Non-fiction".class BookController { def scaffold = Book // overrides scaffolded action to return both authors and books def list = { [ "books" : Book.65) } Restricting the size via a constraint also effects how many characters can be entered in the generated view: def constraints = { name(size:0. "Biography"]) releaseDate() } Or if you use the range constraint on a number: def constraints = { age(range:18. Grails also supports "static" scaffolding which will be discussed in the following sections. Grails allows you to generate a controller and the views used to create the above interface via the command line. To generate a controller type: grails generate-controller Book Or to generate the views type: grails generate-views Book 206 .
207 .Book Customizing the Scaffolding templates The templates used by Grails to generate the controller and views can be customized by installing the templates with the install-templates command.Or to generate everything type: grails generate-all Book If you have a domain class in a package or are generating from a Hibernate mapped class remember to include the fully qualified package name: grails generate-all com.bookstore.
you can add a line to grails-app/conf/BuildConfig.groovy to either lists of Ant include patterns or closures containing AntBuilder syntax. whereas each item in a pattern list is included. As an alternative to the default behavior you can explicitly specify the complete list of libraries to include in the WAR file by setting the properties grails. Be careful with these properties: if any of the libraries Grails depends on are missing. Any closure or pattern assigned to the latter property will be included in addition to grails.war.java5.recompile" to true disables this regular check completely. you can specify a path (either absolute or relative) to the command that instructs it where to place the file and what name to give it: grails war /opt/java/tomcat-5. plus any libraries contained in plugin "lib" directories.24/foobar. Creating a WAR file is as simple as executing the war command: grails war There are also many ways in which you can customise the WAR file that is created. Deployment Grails applications can be deployed in a number of ways. current java infrastructures almost mandate that web applications are deployed as WAR files. plus any libraries contained in the application's "lib" directory.war.5 or above.5. in case you need to avoid conflicts with libraries in a shared folder for example.war.dependencies in Config. Setting the system property "disable. "grails run-war" This is very similar to the previous option. It is also possible to control what libraries are included in the WAR file. since it is the most common method of running an application during the development phase. grails prod run-app removes the per-request overhead and allows you to fine tune how frequently the regular check takes place. any command line argument that you provide overrides this setting.war Alternatively. while the property "recompile. Here is an example that includes a small subset of the standard Grails dependencies: 208 . For example. the application will almost certainly fail.auto. Closures are invoked from within an Ant "copy" step. The default is currently 3.17.groovy that changes the default location and filename: grails.war" Of course. The default behavior is to include in the WAR file all libraries required by Grails. each of which has its pros and cons. so you get good performance without the hassle of having to deploy the WAR file elsewhere. This latter property should be set to the number of seconds you want between each check. An embedded Tomcat server is launched that loads the web application from the development sources. WAR file When it comes down to it. but Tomcat runs against the packaged WAR file rather than the development sources.war.dependencies and grails. This approach is not recommended at all for production deployment because the performance is poor.frequency" controls the frequency.file = "foobar-prod.project. so this is by far the most common approach to Grails application deployment in production. thus allowing it to pick up an changes to application files. Having said that. "grails run-app" You should be very familiar with this approach by now. Checking for and loading changes places a sizable overhead on the server. Hot-reloading is disabled.dependencies only if you are running JDK 1. so only elements like "fileset" can be included.
war.xml") } Application servers Ideally you should be able to simply drop a WAR file created by Grails into any application server and it should work straight away.jar".jar". The Grails website contains an up-to-date list of application servers that Grails has been tested with.war. // Here we override the standard web. along with any additional steps required to get a Grails WAR file working. You can also find a list of the default dependencies included in WAR generation in the "War.war.jar".1. "groovy-all-*. tofile: "${stagingDir}/WEB-INF/web. "standard-${servletVersion}.jar". "xstream-1. The remaining two configuration options available to you are grails. // This closure is passed the command line arguments used to start the // war process.3.see the "DEFAULT_DEPS" and "DEFAULT_J5_DEPS" variables.jar". "sitemesh-*.xml with our own.jar". "ognl-*.4. grails. "xpp3_min-1.resources = { stagingDir. "jstl-${servletVersion}.xml".O. args -> copy(file: "grails-app/conf/custom-web. grails. and the command line arguments. "commons-*. However.each { pattern -> include(name: pattern) } } } This example only exists to demonstrate the syntax for the properties.jar". the application will probably not work.jar" ] grails.copyToWebApp = { args -> fileset(dir:"web-app") { include(name: "js/**") include(name: "css/**") include(name: "WEB-INF/**") } } // This closure is passed the location of the staging directory that // is zipped up to make the WAR file.resources.jar".copyToWebApp and grails. If you attempt to use it as is in your own application. The second allows you to do any extra processing you want before the WAR file is finally created.war.groovy" script . "log4j-*.jar". You can find a list of dependencies required by Grails in the "dependencies. "spring-*. "commons-logging-*. The first of these allows you to customise what files are included in the WAR file from the "web-app" directory.txt" file that resides in the root directory of the unpacked distribution.jar".war.1. things are rarely ever this simple.2.def deps = [ "hibernate3. "oscache-*.dependencies = { fileset(dir: "libs") { deps. Sponsored by SpringSource 209 .jar".jar".
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