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1.1 the state of java EE
The Java EE 6 is the current Java Enterprise Edition specification (as of Oct. 2010). Compared to the previous specification, it introduces several new features:
Profiles, configurations of the Java EE platform targeted at specific classes of applications. Specifically, the Java EE 6 platform introduces a Web Profile targeted at web applications, as well as a Full Profile that contains all Java EE technologies. New technologies, including the following:
• • •
Java API for RESTful Web Services (JAX-RS) Contexts and Dependency Injection for the Java EE Platform (JSR-299), informally known as Web Beans Java Authentication Service Provider Interface for Containers (JASPIC)
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New features for Enterprise JavaBeansTM (EJBTM) components New features for servlets New features for JavaServer TM Faces components
1.2 the application model
The application model starts with the Java programming language and the Java Virtual Machine. This combination provides high portability, scalability and developing efficiency. Java EE is designed to support applications that implement enterprise services for customers, employees, suppliers, partners, and others who make demands on or contributions to the enterprise. Such applications are inherently complex, potentially accessing data from a variety of sources and distributing applications to a variety of clients. To better control and manage these applications, the business functions to support these various users are conducted in the middle tier. The middle tier represents an environment that is closely controlled by an enterprise's information technology department. The middle tier is typically run on dedicated server hardware and has access to the full services of the enterprise. The Java EE application model defines an architecture for implementing services as multi-tier applications that deliver the scalability, accessibility, and manageability needed by enterpriselevel applications. This model partitions the work needed to implement a multi-tier service into two parts: the business and presentation logic to be implemented by the developer, and the standard system services provided by the Java EE platform. The developer can rely on the platform to provide solutions for the hard systems-level problems of developing a multi-tier service.
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1.3 distributed multitiered applications
The Java EE platform uses a distributed multitiered application model for enterprise applications. Application logic is divided into components according to function, and the various application components that make up a Java EE application are installed on different machines depending on the tier in the multitiered Java EE environment to which the application component belongs. Figure 1.1 shows generic multitiered Java EE applications divided into the tiers described in the list below. The Java EE application parts shown in figure 1.1 are presented in the Java EE components section.
• • • •
client-tier components run on the client machine. web-tier components run on the Java EE server. business-tier components run on the Java EE server. enterprise information system (EIS)-tier software runs on the EIS server
Figure 1.1 Distributed multitiered applications
Although a Java EE application can consist of the three or four tiers shown in figure 1.1, Java EE multitiered applications are generally considered to be three-tiered applications because they are distributed over three locations: client machines, the Java EE server machine, and the database or legacy machines at the back end. Three-tiered applications that run in this way extend the standard two-tiered client and server model by placing a multithreaded application server between the client application and back-end storage.
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1.4 java EE components
Java EE applications are made up of components. A Java EE component is a self-contained functional software unit that is assembled into a Java EE application with its related classes and files and that communicates with other components. The Java EE specification defines the following Java EE components:
• • •
Application clients and applets are components that run on the client. Java Servlet, JavaServer Faces, and JavaServer Pages (JSP) technology components are web components that run on the server. Enterprise JavaBeansTM (EJB) components (enterprise beans) are business components that run on the server.
Java EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between Java EE components and "standard" Java classes is that Java EE components are assembled into a Java EE application, are verified to be well formed and in compliance with the Java EE specification, and are deployed to production, where they are run and managed by the Java EE server.
1.5 java EE Clients
A Java EE client can be a web client or an application client.
1.5.1 Web Clients
A web client consists of two parts: (1) dynamic web pages containing various types of markup language (HTML, XML, and so on), which are generated by web components running in the web tier, and (2) a web browser, which renders the pages received from the server. A web client is sometimes called a thin client. Thin clients usually do not query databases, execute complex business rules, or connect to legacy applications. When you use a thin client, such heavyweight operations are off-loaded to enterprise beans executing on the Java EE server, where they can leverage the security, speed, services, and reliability of Java EE server-side technologies.
1.5.2 Applets
A web page received from the web tier can include an embedded applet. An applet is a small client application written in the Java programming language that executes in the Java virtual machine installed in the web browser. However, client systems will likely need the Java Plug-in and possibly a security policy file in order for the applet to successfully execute in the web browser. Web components are the preferred API for creating a web client program because no plug-ins or security policy files are needed on the client systems. Also, web components enable cleaner and more modular application design because they provide a way to separate applications programming from web page design. Personnel involved in web page design thus do not need to understand Java programming language syntax to do their jobs.
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An application client runs on a client machine and provides a way for users to handle tasks that require a richer user interface than can be provided by a markup language. It typically has a graphical user interface (GUI) created from the Swing or the Abstract Window Toolkit (AWT) API, but a command-line interface is certainly possible. Application clients directly access enterprise beans running in the business tier. However, if application requirements warrant it, an application client can open an HTTP connection to establish communication with a servlet running in the web tier. Application clients written in languages other than Java can interact with Java EE 6 servers, enabling the Java EE 6 platform to interoperate with legacy systems, clients, and non-Java languages.
1.5.4 The JavaBeans Component Architecture
The server and client tiers might also include components based on the JavaBeans component architecture (JavaBeans components) to manage the data flow between an application client or applet and components running on the Java EE server, or between server components and a database. JavaBeans components are not considered Java EE components by the Java EE specification. JavaBeans components have properties and have get and set methods for accessing the properties. JavaBeans components used in this way are typically simple in design and implementation but should conform to the naming and design conventions outlined in the JavaBeans component architecture.
1.5.5 Java EE Server Communications
Figure 1.2 shows the various elements that can make up the client tier. The client communicates with the business tier running on the Java EE server either directly or, as in the case of a client running in a browser, by going through JSP pages or servlets running in the web tier. Your Java EE application uses a thin browser-based client or thick application client. In deciding which one to use, you should be aware of the trade-offs between keeping functionality on the client and close to the user (thick client) and off-loading as much functionality as possible to the server (thin client). The more functionality you off-load to the server, the easier it is to distribute, deploy, and manage the application; however, keeping more functionality on the client can make for a better perceived user experience.
are not considered web components. like the client tier. 1. Servlets are Java programming language classes that dynamically process requests and construct responses. processes it (if necessary). Figure 1.7 business components Business code. enterprise edition Figure 1.java platform. retail.2 Server communication 1. like HTML pages. might include a JavaBeans component to manage the user input and send that input to enterprise beans running in the business tier for processing. which is logic that solves or meets the needs of a particular business domain such as banking. and sends it back to the client program.6 web components Java EE web components are either servlets or pages created using JSP technology (JSP pages) and/or Java Server Faces technology.3 shows how an enterprise bean receives data from client programs. 5 .1 . is handled by enterprise beans running in the business tier. or finance. Java Server Faces technology builds on servlets and JSP technology and provides a user interface component framework for web applications. Server-side utility classes can also be bundled with web components and. The web tier. Static HTML pages and applets are bundled with web components during application assembly but are not considered web components by the Java EE specification. JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content. and sends it to the enterprise information system tier for storage. processes it (if necessary). An enterprise bean also retrieves data from storage.
8 enterprise information system tier The enterprise information system tier handles EIS software and includes enterprise infrastructure systems such as enterprise resource planning (ERP). mainframe transaction processing.9 java EE Containers Normally. For example. 1. Business and EIS Tiers 1. or application client component can be executed. Before a web. 6 . the Java EE server provides underlying services in the form of a container for every component type.9. resource pooling. Java EE application components might need access to enterprise information systems for database connectivity.1 . In addition. and other complex low-level details.3 Web. and other legacy information systems. 1. Because you do not have to develop these services yourself. you are free to concentrate on solving the business problem at hand. it must be assembled into a Java EE module and deployed into its container. database systems. enterprise bean. multithreading. The component-based and platform-independent Java EE architecture makes Java EE applications easy to write because business logic is organized into reusable components. enterprise edition Figure 1. thin-client multitiered applications are hard to write because they involve many lines of intricate code to handle transaction and state management.java platform.1 Container Services Containers are the interface between a component and the low-level platform-specific functionality that supports the component.
7 .java platform. The container also manages nonconfigurable services such as enterprise bean and servlet life cycles. enterprise edition The assembly process involves specifying container settings for each component in the Java EE application and for the Java EE application itself. The Java EE transaction model lets you specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit. For example.2 Container Types The deployment process installs Java EE application components in the Java EE containers illustrated in figure 1. including services such as security.1 . a client invokes methods on it as if it were in the same virtual machine. The Java EE remote connectivity model manages low-level communications between clients and enterprise beans.9. and remote connectivity. JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access these services. Container settings customize the underlying support provided by the Java EE server. 1. Because the Java EE architecture provides configurable services. an enterprise bean can have security settings that allow it a certain level of access to database data in one production environment and another level of database access in another production environment. Java Naming and Directory Interface (JNDI) lookups. application components within the same Java EE application can behave differently based on where they are deployed. transaction management. database connection resource pooling. and access to the Java EE platform APIs.4. Here are some of the highlights: • • • • The Java EE security model lets you configure a web component or enterprise bean so that system resources are accessed only by authorized users. data persistence. After an enterprise bean is created.
and use XML stylesheets to manage the display and handling of the data. Web container . and deploy web services and clients that fully interoperate with other web services and clients running on Java-based or non-Java-based platforms. Application client container . Application clients and their container run on the client.java platform. Another company might read the XML pricing information into an application for processing. These XML-based standards and protocols are introduced in the following sections.10. The translation of data to a standardized XML-based data stream is what makes web services and clients written with the Java EE XML APIs fully interoperable. computeraided design (CAD) documents and the like. maps.the runtime portion of a Java EE product. The Java EE platform provides the XML APIs and tools you need to quickly design. video. or for document-oriented web services.manages the execution of enterprise beans for Java EE applications.manages the execution of application client components. text-based standard for representing data. enterprise edition Figure 1. Enterprise beans and their container run on the Java EE server. program files. and companies that receive the price lists and schema can have their own stylesheets to handle the data in a way that best suits their needs.manages the execution of applets. 1.1 XML XML is a cross-platform. Applet container . or any kind of binary data such as audio. Here are examples: • • • One company might put XML pricing information through a program to translate the XML to HTML so that it can post the price lists to its intranet. Enterprise JavaBeans (EJB) container . A Java EE server provides EJB and web containers. No low-level programming is needed because the XML API implementations do the work of translating the application data to and from an XML-based data stream that is sent over the standardized XML-based transport protocols.4 Java EE Server and Containers • • • • • Java EE server .1 .manages the execution of JSP page and servlet components for Java EE applications. XML data. To write web services and clients with the Java EE XML APIs. Consists of a web browser and Java Plug-in running on the client together. 8 . 1. For example. test. set up schemas to specify which tags can be used in a particular kind of XML document.10 support for web services Web services are web-based enterprise applications that use open. The next section introduces XML and explains how parties doing business can use XML tags and schemas to exchange data in a meaningful way. develop. all you do is pass parameter data to the method calls and process the data returned. When XML data is exchanged between parties. a web service can use XML and a schema to produce price lists. This does not necessarily mean that the data being transported includes XML tags because the transported data can itself be plain text. Web components and their container run on the Java EE server. the parties are free to create their own tags to describe the data. A partner company might put the XML pricing information through a tool to create a marketing presentation. extensible. XML-based standards and transport protocols to exchange data with calling clients. you send documents containing the service data back and forth.
11 java EE 6 core technologies and APIs Figure 1. The following sections give a brief summary of the technologies required by the Java EE platform.10. all running on different platforms and at various locations on the Internet. 9 . where the information can be readily and globally accessed by clients who want to do business. enterprise edition 1.3 WSDL Standard Format The Web Services Description Language (WSDL) is a standardized XML format for describing network services. 1. The SOAP portion of a transported message handles the following: • • • Defines an XML-based envelope to describe what is in the message and how to process the message Includes XML-based encoding rules to express instances of application-defined data types within the message Defines an XML-based convention for representing the request to the remote service and the resulting response 1. HTTP is a familiar request-and response standard for sending messages over the Internet. The description includes the name of the service.2 SOAP Transport Protocol Client requests and web service responses are transmitted as Simple Object Access Protocol (SOAP) messages over HTTP to enable a completely interoperable exchange between clients and web services.4 UDDI and ebXML Standard Formats Other XML-based standards. make it possible for businesses to publish information on the Internet about their products and web services.10.10.1 . such as Universal Description. Discovery and Integration (UDDI) and ebXML. and the APIs used in Java EE applications. and SOAP is an XML-based protocol that follows the HTTP request-and-response model. 1. and ways to communicate with the service.java platform. WSDL service descriptions can be stored in UDDI registries or published on the web (or both). the location of the service.5 illustrates the availability of the Java EE 6 platform APIs in each Java EE container type. The Sun Java System Application Server Platform Edition 8 provides a tool for generating the WSDL specification of a web service that uses remote procedure calls to communicate with clients.
Although servlets can respond to any type of request.1 . WML. allowing a business component to receive messages asynchronously. is a body of code having fields and methods to implement modules of business logic.java platform. An entity represents persistent data stored in one row of a database table. 1.11. these are Java Message Service (JMS) messages. Commonly. A JSP page is a text-based document that contains two types of text: static data (which can be expressed in any text-based format such as HTML. When the client finishes executing. standard set of tags. or if the server shuts down. which determine how the page constructs dynamic content. If the client terminates. There are two kinds of enterprise beans: session beans and message-driven beans. or enterprise bean. enterprise edition Figure 1.5 Java EE Platform APIs 1.3 JavaServer Pages Technology JavaServer Pages (JSP) technology lets you put snippets of servlet code directly into a textbased document. entity beans have been replaced by Java persistence API entities. A session bean represents a transient conversation with a client. Instead of mixing tags from numerous vendors in your JSP applications.11. A message-driven bean combines features of a session bean and a message listener. A servlet class extends the capabilities of servers that host applications that are accessed by way of a request-response programming model.11. you employ a single. You can think of an enterprise bean as a building block that can be used alone or with other enterprise beans to execute business logic on the Java EE server. This standardization allows you to deploy your applications on any JSP container that supports JSTL and makes it more likely that the 10 .11.4 JavaServer Pages Standard Tag Library The JavaServer Pages Standard Tag Library (JSTL) encapsulates core functionality common to many JSP applications. the session bean and its data are gone. and XML) and JSP elements. 1.2 Java Servlet Technology Java servlet technology lets you define HTTP-specific servlet classes. the persistence manager ensures that the entity data is saved. 1. they are commonly used to extend the applications hosted by web servers. In Java EE 5.1 Enterprise JavaBeans Technology An Enterprise JavaBeans (EJB) component.
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implementation of the tags is optimized. JSTL has iterator and conditional tags for handling flow control, tags for manipulating XML documents, internationalization tags, tags for accessing databases using SQL, and commonly used functions.
1.11.5 JavaServer Faces
JavaServer Faces technology is a user interface framework for building web applications. The main components of JavaServer Faces technology are as follows:
• •
A GUI component framework. A flexible model for rendering components in different kinds of HTML or different markup languages and technologies. A Renderer object generates the markup to render the component and converts the data stored in a model object to types that can be represented in a view. A standard RenderKit for generating HTML/4.01 markup. Input validation Event handling Data conversion between model objects and components Managed model object creation Page navigation configuration
The following features support the GUI components:
• • • • •
All this functionality is available via standard Java APIs and XML-based configuration files.
1.11.6 Java Message Service API
The Java Message Service (JMS) API is a messaging standard that allows Java EE application components to create, send, receive, and read messages. It enables distributed communication that is loosely coupled, reliable, and asynchronous.
1.11.7 Java Transaction API
The Java Transaction API (JTA) provides a standard interface for demarcating transactions. The Java EE architecture provides a default auto commit to handle transaction commits and rollbacks. An auto commit means that any other applications that are viewing data will see the updated data after each database read or write operation. However, if your application performs two separate database access operations that depend on each other, you will want to use the JTA API to demarcate where the entire transaction, including both operations, begins, rolls back, and commits.
1.11.8 JavaMail API
Java EE applications use the JavaMail API to send email notifications. The JavaMail API has two parts: an application-level interface used by the application components to send mail, and a service provider interface. The Java EE platform includes JavaMail with a service provider that allows application components to send Internet mail.
1.11.9 JavaBeans Activation Framework
The JavaBeans Activation Framework (JAF) is included because JavaMail uses it. JAF provides standard services to determine the type of an arbitrary piece of data, encapsulate access to it, discover the operations available on it, and create the appropriate JavaBeans component to
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perform those operations.
1.11.10 Java API for XML Processing
The Java API for XML Processing (JAXP), part of the Java SE platform, supports the processing of XML documents using Document Object Model (DOM), Simple API for XML (SAX), and Extensible Stylesheet Language Transformations (XSLT). JAXP enables applications to parse and transform XML documents independent of a particular XML processing implementation. JAXP also provides namespace support, which lets you work with schemas that might otherwise have naming conflicts. Designed to be flexible, JAXP lets you use any XML-compliant parser or XSL processor from within your application and supports the W3C schema. You can find information on the W3C schema at this URL: http://www.w3.org/XML/Schema.
1.11.11 Java API for XML Web Services (JAX-WS)
The JAX-WS specification provides support for web services that use the JAXB API for binding XML data to Java objects. The JAX-WS specification defines client APIs for accessing web services as well as techniques for implementing web service endpoints. The Web Services for J2EE specification describes the deployment of JAX-WS-based services and clients. The EJB and servlet specifications also describe aspects of such deployment. It must be possible to deploy JAX-WS-based applications using any of these deployment models. The JAX-WS specification describes the support for message handlers that can process message requests and responses. In general, these message handlers execute in the same container and with the same privileges and execution context as the JAX-WS client or endpoint component with which they are associated. These message handlers have access to the same JNDI java:comp/env namespace as their associated component. Custom serializers and deserializers, if supported, are treated in the same way as message handlers.
1.11.12 Java API for RESTful Web Services (JAX-RS)
The Java API for RESTful Web Services (JAX-RS) defines APIs for the development of Web services built according to the Representational State Transfer (REST) architectural style. A JAXRS application is a web application that consists of classes that are packaged as a servlet in a WAR file along with required libraries. The JAX-RS API is new to the Java EE 6 platform.
1.11.13 Java Architecture for XML Binding (JAXB)
The Java Architecture for XML Binding (JAXB) provides a convenient way to bind an XML schema to a representation in Java language programs. JAXB can be used independently or in combination with JAX-WS, where it provides a standard data binding for web service messages. All Java EE application client containers, web containers, and EJB containers support the JAXB API.
1.11.14 SOAP with Attachments API for Java
The SOAP with Attachments API for Java (SAAJ) is a low-level API on which JAX-WS and JAXR depend. SAAJ enables the production and consumption of messages that conform to the SOAP 1.1 specification and SOAP with Attachments note. Most developers do not use the SAAJ API, instead using the higher-level JAX-WS API.
1.11.15 Java API for XML Registries
The Java API for XML Registries (JAXR) lets you access business and general-purpose registries over the web. JAXR supports the ebXML Registry and Repository standards and the
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emerging UDDI specifications. By using JAXR, developers can learn a single API and gain access to both of these important registry technologies. Additionally, businesses can submit material to be shared and search for material that others have submitted. Standards groups have developed schemas for particular kinds of XML documents; two businesses might, for example, agree to use the schema for their industry's standard purchase order form. Because the schema is stored in a standard business registry, both parties can use JAXR to access it.
1.11.16 J2EE Connector Architecture
The J2EE Connector architecture is used by tools vendors and system integrators to create resource adapters that support access to enterprise information systems that can be plugged in to any Java EE product. A resource adapter is a software component that allows Java EE application components to access and interact with the underlying resource manager of the EIS. Because a resource adapter is specific to its resource manager, typically there is a different resource adapter for each type of database or enterprise information system. The J2EE Connector architecture also provides a performance-oriented, secure, scalable, and message-based transactional integration of Java EE-based web services with existing EISs that can be either synchronous or asynchronous. Existing applications and EISs integrated through the J2EE Connector architecture into the Java EE platform can be exposed as XML-based web services by using JAX-WS and Java EE component models. Thus JAX-WS and the J2EE Connector architecture are complementary technologies for enterprise application integration (EAI) and end-to-end business integration.
1.11.17 Java Database Connectivity API
The Java Database Connectivity (JDBC) API lets you invoke SQL commands from Java programming language methods. You use the JDBC API in an enterprise bean when you have a session bean access the database. You can also use the JDBC API from a servlet or a JSP page to access the database directly without going through an enterprise bean. The JDBC API has two parts: an application-level interface used by the application components to access a database, and a service provider interface to attach a JDBC driver to the Java EE platform.
1.11.18 Java Persistence API
The Java Persistence API is a new all Java standards based solution for persistence. Persistence uses an object-relational mapping approach to bridge the gap between an object oriented model and a relational database. Java Persistence consists of three areas:
• • •
The Java Persistence API The query language Object/relational mapping metadata
1.11.19 Java Naming and Directory Interface
The Java Naming and Directory Interface (JNDI) provides naming and directory functionality, enabling applications to access multiple naming and directory services, including existing naming and directory services such as LDAP (Lightweight Directory Access Protocol), NDS (Novell Directory Services), DNS, and NIS (Network Information services). It provides applications with methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes. Using JNDI, a Java EE application can store and retrieve any type of named Java object, allowing Java EE applications to coexist with many legacy applications and systems.
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Java EE naming services provide application clients, enterprise beans, and web components with access to a JNDI naming environment. A naming environment allows a component to be customized without the need to access or change the component's source code. A container implements the component's environment and provides it to the component as a JNDI naming context. A Java EE component can locate its environment naming context using JNDI interfaces. A component can create a javax.naming.InitialContext object and looks up the environment naming context in InitialContext under the name java:comp/env. A component's naming environment is stored directly in the environment naming context or in any of its direct or indirect subcontexts. A Java EE component can access named system-provided and user-defined objects. The names of system-provided objects, such as JTA UserTransaction objects, are stored in the environment naming context, java:comp/env. The Java EE platform allows a component to name user-defined objects, such as enterprise beans, environment entries, JDBC DataSource objects, and message connections. An object should be named within a subcontext of the naming environment according to the type of the object. For example, enterprise beans are named within the subcontext java:comp/env/ejb, and JDBC DataSource references in the subcontext java:comp/env/jdbc.
1.11.20 Java Authentication and Authorization Service
The Java Authentication and Authorization Service (JAAS) provides a way for a Java EE application to authenticate and authorize a specific user or group of users to run it. JAAS is a Java programming language version of the standard Pluggable Authentication Module (PAM) framework, which extends the Java Platform security architecture to support userbased authorization.
1.11.21 Java Authorization Service Provider Contract for Containers (Java ACC)
The Java ACC specification defines a contract between a Java EE application server and an authorization policy provider. All Java EE containers support this contract. The Java ACC specification defines java.security.Permission classes that satisfy the Java EE authorization model. The specification defines the binding of container access decisions to operations on instances of these permission classes. It defines the semantics of policy providers that employ the new permission classes to address the authorization requirements of the Java EE platform, including the definition and use of roles.
1.11.22 Java Authentication Service Provider Interface for Containers (JASPIC)
The Java Authentication Service Provider Interface for Containers (JASPIC) specification defines a service provider interface (SPI) by which authentication providers that implement message authentication mechanisms may be integrated in client or server message processing containers or runtimes. Authentication providers integrated through this interface operate on network messages provided to them by their calling container. They transform outgoing messages so that the source of the message may be authenticated by the receiving container, and the recipient of the message may be authenticated by the message sender. They authenticate incoming messages and return to their calling container the identity established as a result of the message authentication.
1.11.23 Simplified Systems Integration
The Java EE platform is a platform-independent, full systems integration solution that creates
module. a standard Java Archive (JAR) file with an . or applet) An optional deployment descriptor that describes its content Once a Java EE unit has been produced. or a component. a module. and JAX-WS Simplified interoperability with the J2EE Connector architecture Easy database connectivity with the JDBC API Enterprise application integration with message-driven beans and JMS. and JNDI 1. Once deployed on a local platform. it can be changed without the need to modify the source code. At runtime. enterprise edition an open marketplace in which every vendor can sell to every customer. Using EAR files and modules makes it possible to assemble a number of different Java EE applications using some of the same components.12 java EE application assembly and deployment A Java EE application is packaged into one or more standard units for deployment to any Java EE platform-compliant system. Each unit contains: • • A functional component or components (such as an enterprise bean. better tools.1 . or component accordingly. Deployment typically involves using a platform's deployment tool to specify location-specific information.xml extension that describes the deployment settings of an application. it is ready to be deployed. servlet. The Java EE 6 APIs enable systems and applications integration through the following: • • • • • • • Unified application model across tiers with enterprise beans Simplified request-and-response mechanism with JSP pages and servlets Reliable security model with JAAS XML-based data interchange integration with JAXP. the application is ready to run. A deployment descriptor is an XML document with an . or better customer support. A Java EE application is delivered in an Enterprise Archive (EAR) file.ear extension. it is only a matter of assembling (or packaging) various Java EE modules into Java EE EAR files.java platform. SAAJ. Because deployment descriptor information is declarative. Such a marketplace encourages vendors to compete. such as better performance. JTA. such as a list of local users that can access it and the name of the local database. An EAR file contains Java EE modules and deployment descriptors. JSP page. No extra coding is needed. 15 . not by trying to lock customers into their technologies but instead by trying to outdo each other in providing products and services that benefit customers. the Java EE server reads the deployment descriptor and acts upon the application.
which contain all Java interfaces. the Sun Java System Application Server Platform Edition 9 runtime deployment descriptor contains information such as the context root of a web application. supporting class files.rar (resource adapter archive) extension. Resource adapter modules. A Java EE module without an application deployment descriptor can be deployed as a stand-alone module. GIF and HTML files. An enterprise bean module deployment descriptor. JSP files. these implement the Connector architecture (see J2EE Connector Architecture) for a particular EIS. • • 16 . Web modules are packaged as JAR files with a . and a web application deployment descriptor.6 EAR file structure There are two types of deployment descriptors: Java EE and runtime.1 . which contain class files and an application client deployment descriptor. A Java EE deployment descriptor is defined by a Java EE specification and can be used to configure deployment settings on any Java EE-compliant implementation. and Application Server implementation-specific parameters. which contain servlet class files. which contain class files for enterprise beans and an EJB deployment descriptor. For example. The Application Server runtime deployment descriptors are named sunmoduleType.jar extension. classes. the mapping of portable names of an application's resources to the server's resources. Web modules. Application client modules are packaged as JAR files with a .java platform. EJB modules are packaged as JAR files with a .war (Web ARchive) extension. enterprise edition Figure 1.xml and are located in the same META-INF directory as the Java EE deployment descriptor. A runtime deployment descriptor is used to configure Java EE implementation-specific parameters. along with the resource adapter deployment descriptor. Resource adapter modules are packaged as JAR files with an . declares transaction attributes and security authorizations for an enterprise bean. A Java EE module consists of one or more Java EE components for the same container type and one component deployment descriptor of that type. The four types of Java EE modules are as follows: • • EJB modules.jar extension. such as caching directives. and other documentation. for example. native libraries. Together. Application client modules.
HTTP was created by by Tim Berners-Lee in 1990 at CERN as a mean to store scientific data. 2.0 – dates from 05/95 and is the object of RFC 1945 (www. we recommend www. as follows: 1.html). zero or more header lines 3. an initial line 2. These messages may have different contents... The first oficial version – HTTP 1. The server answers with a response message.jmarshall. namely HTTP 1. a blank line (CR/LF) 4. was the object of several RFCs. of which we mention RFC 2068 (01/97). It is authored by Tim Berners-Lee. Roy Fielding and Henrik Nielsen. separated by spaces: • • a command (method) name (like GET. The client sends a request message to the server.1.ietf.) a file specification (path) (the part of the URL after the host name) 17 . The second (and last.HTTP 2. . but they also have some common structural elements. As a site for understanding how HTTP works.w3..org/Protocols . check the official HTTP site – www. It quickly evolved into the preferred communication protocol over the internet. so far) version. RFC 2617 (06/99) and RFC 2774 (02/00). POST.1 what is http HTTP stands for HyperText Transfer Protocol while hypertext means text contatining links to another text. RFC 2616 (06/99). For a complete specification of the different HTTP versions.apps.com/easy/http..2 .HTTP 2 .3 the initial request line Contains 3 elements.2 the structure of http transactions HTTP follows the client – server model. HEAD. Headern: valuen <optional data block> 2. an optional message body <initial line> Header1: value1 .org/rfc/rfc1945.
POST 4.5 the GET and POST methods The GET method means retrieve whatever information (in the form of an entity) is identified by the Request-URI. GET /path/to/the/file/index. If the Request-URI refers to a data-producing process. These commands are: • • • LINK UNLINK PATCH The HEAD command is identical to the GET command in all respects but one. The only difference is that the response must not have a body.0 Here is an example of an initial request line: 2. DELETE 6.Annotation of existing resources. it is the produced data which shall be returned as the entity in the response and not the source text of the process. there are 8 HTTP commands (methods) that are widely supported.0). GET 2.4 http commands (methods) As of HTTP 1. newsgroup. POST is designed to allow a uniform method to cover the following functions: . . but lack of support makes them obsolete. as well.1. All the information requested is returned in the header section of the response.html HTTP/1. TRACE Three other commands are listed. HEAD 3. Here is their list: 1.Posting a message to a bulletin board. 18 . 2. in the HTTP 1. HTTP/1.1 specification. PUT 8. CONNECT 5. mailing list.HTTP • the HTTP version (usually. The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line. OPTIONS 7. unless that text happens to be the output of the process.2 .
separated by spaces (although the reason phrase may contain spaces. GET attaches this data to the URL of the request. form data submitted by POST may be encoded either as above (using application/x-www-form-urlencoded content type). or in the message body. or a record is subordinate to a database. to a data-handling process. as well): • • • the HTTP version of the response a response status code (a number) a response status reason phrase (a human readable response status) Here is an example of an initial response line: HTTP/1. (encoded as multipart/form-data). 2. depending on whether or not the response includes an entity that describes the result. . When used for form data submission. The posted entity is subordinate to that URI in the same way that a file is subordinate to a directory containing it.0 404 Not Found 2.8 the status code A three-digit integer. where the first digit identifies the general category of response: • 1xx indicates an informational message only 19 . as a sequence of "name=value" pairs. The action performed by the POST method might not result in a resource that can be identified by a URI." On the other side.2 . A POST request requires an extra transmission to retrieve the message body. either 200 (OK) or 204 (No Content) is the appropriate response status. 2. In this case. The method GET is intended for getting (retrieving) data. The actual function performed by the POST method is determined by the server and is usually dependent on the Request-URI. such as the result of submitting a form.6 differences between GET and POST 1. . after the "?" character. separated by the character "&" or ".Providing a block of data. or ordering a product. like storing or updating data.HTTP or similar group of articles.7 the initial response (status) line Contains 3 elements. while POST may involve anything. 3. while a GET request allows data sent via the URL to be processed immediately. or sending E-mail 2.Extending a database through an append operation. a news article is subordinate to a newsgroup to which it is posted.
The HTTP 1.10 the message body An HTTP message may have a body of data sent after the header lines. 404 Not Found . fails. • • the Content-Type: header gives the MIME-type of the data in the body.0. In a request. that is. or otherwise can't run correctly. and the resulting resource (e. such as text/html or image/jpg. 2.9 header lines A header line consists of two parts. The most common cause is a server-side script that has bad syntax.g.2 .the resource has moved to another URL (given by the Location: response header). the header lines of the message are used to describe the body.1). or perhaps explanatory text if there's an error.0Gold Last-Modified: Fri. 2. In particular. where the requested resource is returned to the client. 20 . file or script output) is returned in the message body. 31 Dec 1999 23:59:59 GMT Header lines which begin with spaces or tabs are parts of the previous header line. If an HTTP message includes a body. none of them mandatory. The most common status codes are: • • • • • • A complete list of status codes is in the HTTP specification (the URL was mentioned in the firs section of this chapter) (section 9 for HTTP 1. header name and header value. 500 Server Error . Although the header names are not case sensitive. the Content-Length: header gives the number of bytes in the body. and should be automatically retrieved by the client. 301 Moved Permanently 302 Moved Temporarily 303 See Other (HTTP 1. this is where user-entered data or uploaded files are sent to the server. This is often used by a CGI script to redirect the browser to an existing file.the requested resource doesn't exist. separated a semicolon.0 version specifies 16 headers. header values are. while the HTTP 1. The most common use of the message body is in a response.an unexpected server error. out of which. A couple of examples of header lines: User-agent: Mozilla/3.1 only) . and section 10 for HTTP 1.the request succeeded.1 version specifies 46 of them. one (Host) is mandatory.HTTP • • • • 2xx indicates success of some kind 3xx redirects the client to another URL 4xx indicates an error on the client's part 5xx indicates an error on the server's part 200 OK .
multipart. 21 . audio. 31 Dec 1999 23:59:59 GMT Content-Type: text/html Content-Length: 1354 <html> <body> <h1>Happy birthday!</h1> (more file contents) . with subtype plain 2. application. message. partial. .info. although the list of admissible subtypes is much longer.11 mime types/subtypes MIME stands for Multipurpose Internet Mail Extensions. Each extension consists of a type and a subtype.HTTP 2. Then. alternative. 1. image.info.uvt. RFC 1521 (www. with subtypes rfc822.ro. video.uvt. text. with subtype mpeg 2. digest.apps.2 .0 From: email@example.com) defines 7 types and several subtypes.html first open a socket to the host web.com User-Agent: HTTPTool/1. external-body 4.0 [blank line here] The server should respond with something like the following.0 200 OK Date: Fri.html HTTP/1. postscript 5. with subtypes jpeg.ietf. port 80 (use the default port of 80 because none is specified in the URL). with subtype basic 7. parallel 3. with subtypes octet-stream. gif 6.org/rfc/rfc1521. send something like the following through the socket: GET /path/file. sent back through the same socket: HTTP/1.12 an example of an http transaction To retrieve the file at the URL http://web.ro/path/file. together with the subtypes defined in this particular RFC. Here is the list of the seven types. with subtypes mixed.
</body> </html> After sending the response. 22 .2 . the server closes the socket.HTTP .
Since it fits in a couple of pages.com/indexdot/html . www. Version 4. Other helpful sites .blooberry. Mosaic.HTML 3.HTML 3 . However.com/tutors. 3. It is a special version of SGML (Standard Generalized Markup Language – an ISO standard (ISO 8879)).0 draft was released in 01.2 language definition HTML is a system for describing documents. images and other components are to be displayed in a browser. From 1999 on.0 was not widely accepted) appeared a W3C recommendation in January 1997.htmlgoodies.www.jmarshall. using a variety of tags and their related attributes. The latest version (XHTML 2. It might take several years before the specification reaches final Recommendation status. All markup languages defined in SGML are called SGML applications and are characterized by: 1. namely HTML 5 was published in January 2008. The first version of HTML. Originally named Web Applications 1.org/rfc/rfc1866.02 and is not intended to be backwards compatible. The first official version – HTML 2. HTML 3.html) and was widely supported.01 With support for the first 17 planes of ISO 10646 and increased limits for tag and literal lengths etc.w3.0) dates from 08.org/Markup .apps. The newest version of HTML is 4.com/easy/html .html. appeared in summer 1991 and was supported by the first popular web browser. namely HTML 1. As a practical reference site use – www.0. a working draft for the next major revision.0 and was accepted in December 1997. The SGML declaration of the latest version of HTML (4. The XHTML 1. -CHARSET BASESET "ISO Registration Number 177//CHARSET ISO/IEC 10646-1:1993 UCS-4 with implementation level 3//ESC 2/5 2/15 4/6" 23 . <!SGML "ISO 8879:1986" -SGML Declaration for HyperText Markup Language version HTML 4.0 .ietf. A newer standard.0.0 introduces the Cascading Style Sheets.2 (3. check the official HTML site – www. the specification includes several ideas of the WHAT (Web Hypertext Application Technology) working group.3 .org/TR/1999/PR-html40-19990824/sgml/sgmldecl. For a complete specification of the different HTML versions.01) can be found at this address: http://www. It is a revision of 4.was approved as a standard in September 1995 (as RFC 1866 (http://www.01.w3c. HTML describes how text. HTML is part of a new specification – XHTML. An SGML declaration – what characters and delimiters may appear. we can afford to have a look at this declaration.1 what is html? HTML stands for HyperText Markup Language.99.
permitted in the declaration NAMELEN 65536 -.-_:" ".increased -ATTSPLEN 65536 -.Avoid fixed limits in actual PILEN 65536 -.3 .SURROGATES -- SGMLREF TOTALCAP GRPCAP ENTCAP SCOPE DOCUMENT SYNTAX SHUNCHAR CONTROLS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127 BASESET "ISO 646IRV:1991//CHARSET International Reference Version (IRV)//ESC 2/8 4/2" DESCSET 0 128 0 FUNCTION RE RS SPACE TAB SEPCHAR LCNMSTRT UCNMSTRT LCNMCHAR UCNMCHAR NAMECASE 13 10 32 9 NAMING "" "" ".implementations of HTML UA's TAGLVL 100 TAGLEN 65536 GRPGTCNT 150 GRPCNT 64 FEATURES MINIMIZE DATATAG OMITTAG RANK SHORTTAG LINK ----- NO YES NO YES 24 .-_:" GENERAL YES ENTITY NO DELIM GENERAL SGMLREF SHORTREF SGMLREF NAMES SGMLREF QUANTITY SGMLREF ATTCNT 60 -.These are the largest values LITLEN 65536 -.HTML DESCSET 0 9 11 13 14 32 127 128 160 55296 57344 CAPACITY 9 2 2 1 18 95 1 32 55136 2048 1056768 UNUSED 9 UNUSED 13 UNUSED 32 UNUSED UNUSED 160 UNUSED 57344 150000 150000 150000 -.
If you wonder what a character reference is. This specification adds new syntactic restrictions which cannot be defined within the frame of the DTD. look at these examples: "<".w3.0 contains an SGML declaration. <><> --> 25 . like ALIGN." (in hexadecimal) . A Document Type Definition (DTD) – defines the syntax of markup constructs. BORDER. Document instances containing data (content) and markup.org/TR/REC-html40/sgml/dtd.3 html elements An HTML element consists of: • • • a start tag a content an end tag One exception. A specification that describes the semantics to be ascribed to the markup and character entity references. An example: <IMG SRC="/images/logo. 3. HTML 4.acesta este un comentariu. A comment section in an HTML document starts with <!-.and end at the first occurrence of -->.01 specification. three DTDs (HTML 4. DYNSRC.gif" ALT="logo" HEIGHT=40 WIDTH=120> declares an image element. Check the address http://www. HTML 4. the specification of HTML 4. """.3 . the element <BR> has no content and no end tag. An example: <!-. This section deals with some of the most common elements. 3. ….0 Transitional DTD.html for the latest version of the HTML DTD.HTML SIMPLE NO IMPLICIT NO EXPLICIT NO OTHER CONCUR NO SUBDOC NO FORMAL YES APPINFO NONE > 2. There are 91 elements defined in the HTML 4. CONTROLS. "水. The start tag of the element contains the values of the (required or optional) attributes of the element. 4.0 Strict DTD. though. Each instance contains a reference to the DTD to be used to interpret it. You get the point.the chinese character for water. Other optional attributes of the <IMG> element. VSAPCE are omitted. Overall.0 Frameset DTD) and a list of character references. with the required (mandatory) attributes SRC and ALT and the optional attributes HEIGHT and WIDTH.
NAME.uvt. Example: <A HREF="http://web.HTML 3. etc.3.2 The <IMG> element Main attributes: • • • • ALT – required.) in order to use it as a destination in a hyperlink or another URL call.php">Login to web mail</A> 3.3.3 .ro/webmail/src/login. indicates the URL to reference the graphic HEIGHT WIDTH 3. Main attributes: • • HREF – specifies the absolute or relative URL of the hyperlink NAME – assigns a symbolic name to the enclosed object (text. An HTML document consists of the parts: • • the <HEAD> part the <BODY> part A minimal HTML document example: <HTML> <HEAD>My Page </HEAD> <BODY>Empty Body </BODY> </HTML> 3.info. specifies the text to be displayed in case source is not found SRC – required.4 the minimal structure of an html document All HTML documents start with the <HTML> tag and end with the corresponding end tag </HTML>.5 tables 26 .1 The <A> element Must contain one of the 2 attributes – HREF. image.
Usually.6 table related elements The specific elements defining a table. columns.3 . Here is their description and attributes. its rows. the <TABLE> element attributes: • • • • • • • • • • • • BORDER CELLSPACING CELLPADDING WIDTH ALIGN VALIGN TBODY BORDERCOLOR FRAME RULES COLORGROUP BACKGROUND the <THEAD> element attributes: • • • • ALIGN BGCOLOR CHAR CHAROFF 27 . <THEAD>. headers and cells are <TABLE>.HTML A table is a visual rectangular object consisting of several rows and columns. <TH> and <TD>. <TR>. the cells in the first row contain are called headers and consist of a brief description of the content of the corresponding column. The intersection of any row and any column is called a cell. Here is a an example of a table: 3.
The <FORM> element has the following attributes: • ACTION .required. specifies the URL of the server side process that will receive the data 28 .HTML • VALIGN the <TH> element attributes: • • • • • • ABBR AXIS CHAR CHAROFF HEADERS SCOPE the <TR> element attributes: • • • • • ALIGN BGCOLOR CHAR CHAROFF VALIGN the <TD> element attributes: • • • • • • • • • ABBR ALIGN CHAR CHAROFF COLSPAN ROWSPAN SCOPE VALIGN WIDTH 3.3 .7 forms A form is a basic component container. allowing user input and parameter submittal.
specifies the type of the input which can have one of the following values: "text". "text/plain" • • 3. "GET" .used with forms that contain a file-selection field.maximum number of options visible to the user.sends the form values in 2 steps: contacts first the server then the form values are sent in a separate transmission. The pairs name=value are separated by ampersand . "hidden".8. allows multiple selections from the choice list. 3. Other possible values for this attribute: "multipart/form-data" .& or (sometimes) by semicolon .8 form related elements 3. specifies how data will be sent to the server. Example: http://web.required.8. "radio".the default value.1 the <INPUT> element Defines input fields for the form. specifies the parameter name. NAME . "password".specifies the encoding type of the of the form content. Main attributes: • TYPE .ro/servlet/MyServlet?a=12&b=25 • ENCTYPE . Possible values for this attribute: • • "POST". "image". Default value: • "application/x-www-form-urlencoded" .3 . Each of the listed choices is an OPTION element.:.sends the form values in a single transmission. either as a drop-down menu or as a list box. where 'HH' is the hexadecimal ASCII code of the character. Main attributes: 29 . the browser appends the values to the URL. "reset".uvt. "checkbox". may have the values GET or POST. data is sent as a single document with multiple sections. Main attributes: • • • NAME MULTIPLE . "file". however.required.3 the <OPTION> element Used inside a <SELECT> element to list the selection choices.info.?. "submit".8.HTML • METHOD .if specified.2 the <SELECT> element Used to create a list of choices.required. after a quotation mark . SIZE . • 3. "button". since it converts spaces to '+' and non-alphanumerical to '%HH'.
3 .HTML • SELECTED Example of a <SELECT> element: <SELECT NAME="action" STYLE="font-family: '@Arial Unicode MS' font-size: 11pt"> <OPTION SELECTED>Select Action <OPTION>Make Payment <OPTION>Transfer a balance <OPTION>Change Mailing Address <OPTION>Change e-mail Address <OPTION>Change User Name/Password <OPTION>View Account Activity </SELECT> 30 .
the compilation process occurs. Java source – a file with extension .class 3.4.C:\TW\mySource. The current version (as of 10. The Java interpreter (which is part of the Java Virtual Machine) parses and executes the Java bytecode.java 2. 4.JAVA PRIMER 4 .java. The java interpreter (as part of the JVM) parses and executes the prog1. Inc. The java compiler (javac) translates it to bytecode – prog1. Example: Edit the file prog1. The first time a class is loaded. allows the compilation of the Java source into machine-dependent binary executable.) in 08. following the 1.4 . To overcome this significant shortage.1 history The initial name of this language was OAK and was developed as part of the GREEN project at Sun. The java compiler is (in general) a command line tool. but next time execution is much faster.2 version.class file.JAVA PRIMER 4. a tool named Just In Time compiler. The current version (as of 10.95.2 java the interpreter. project started in 12. In terms of execution time. which accounts for a pretty slow execution.95.90. a Java interpreted program is about 10 times slower than a compiled and linked one.C:\TW\myPackages -g login. -g : generate all debugging info. Java bytecode – a file with extension .class file. with the following main options: • • • • -classpath <path> -sourcepath <path> -d <directory> : specifies where to put the . Early versions of Java were released in 12. A java program goes thru the following phases: 1..2010) of Java Platform Enterprise Edition is Java EE 6 Update 21. javac -classpath . jit From source to execution.3 java applications 31 .94 and was officially announced at Sun World in 05.0.java One example of command line compilation: 4.class. pretty much comparable to that of a binary executable.2004) of Java 2 Platform Standard Edition is J2SE 5. The first commercial version was delivered to the first customer (Netscape.
java.4. A Java class B inherits another class A (or is a subclass of A. or that it extends A). Exactly one of these classes must implement a method called main(). or is derived from A. namely: • • • CODE – identifies the (compiled) class file of the applet WIDTH HEIGHT A java application is a collection of java classes. In general.2 inheritance Inheritance is a partial order relation in the set of all Java classes. each class is implemented in a source file having the same name as the class itself and whose extension is .4. 4. The <APPLET> element has 3 mandatory attributes. Generally. an applet is inserted in a HTML page by an <APPLET> tag or by an <OBJECT> tag. as follows: java [-options] class [args] Where main options are: • • -cp <directories and jar files separated by ".jar file."> : cp = classpath -D <name>=<value> : set a system property To execute a . the others are the standalone programs – Java applications. This binary relation is specified in the declaration of the derived class B using the keyword extends. use the command: java –jar [-options] jarfile [args] 4. The first type are embedded in web pages – applets.4 object oriented concepts 4. A java applet is a java class that extends the standard Applet class.4 .JAVA PRIMER There exist 2 types of programs that can be written in Java.1 encapsulation This is a fancy word for the tendency of hiding the implementation of the methods of some class and exposing only the interface of its public (and to some degree – its protected) methods. An example: 32 . This method is the entry point in the application and must have the following signature: public static void main(String[] args) A compiled java application (class) may be executed from the command line using an executable called java (the java interpreter).
Long. Character. this is called method overloading.1 bit char . all classes in Java are (by default) subclasses of a universal base class. Boolean.4 . Double. Integer. That means that the graph of the direct inheritance relation is a forest (its connected components are trees). While C++ allows multiple inheritance. namely: Byte. a class can have more than one method with the same name. a Java class can extend a single base class. provided that the types (and order) of its parameters are different.5 java as programming language integer data types: • • • • byte short int long float double boolean .Unicode (16 bits) floating point data types: • • other types: • • All basic types have associated classes which extend their functionality. Therefore. 4. Float. 33 .JAVA PRIMER public class CaineComunitar extends Caine { … } In this case. The derived class B can use (for free) all the methods of the base class. 4. 4. all variables and methods of the base class A are automatically variables and methods of the derived class B. In fact. the forest we mentioned is actually a tree.4 Method overloading A method (which has to be declared in some class (or interface)) is identified by its name and the type sequence of its parameters.4. with the root the class Object. but it also can override the implementation of any method in the base class. The return type of a method is not part of this signature. Short. providing its own implementation. called Object. In OO jargon.3 Polymorphism Polymorphism means the ability of a variable of a given (base) type (class) to be used to reference objects of different (derived) types (classes). Therefore.4. and automatically call the method specific to the type (derived class) of the object that the variable references.
they have the same basic meaning as in C++. • • • • no specifier . anywhere abstract .all variables referenced in the function body are static variables.http.one which is constant method . no templates.4 . The modifiers of the variables and methods of a class specify their range and stability. automatic garbage collection.http. A final variable (method. } declares an abstract class.. More precisely: A static (or class): • • variable . which is visible only to the classes in the same package. class . Except for the "package" concept.HttpServlet implements Serializable { . the specifiers for the class itself can be taken from the following list: • • • no specifier . 4.one which is defined at class level.the default value makes the class visible only to the classes in the same package public .6 access specifiers and modifiers in java The access attributes of a member variable or method of a class are specified by the access specifiers. class) is one which cannot be modified (overridden. method .the method implementation cannot be overriden by some subclass.JAVA PRIMER Other peculiarities: no pointers (only references). A static variable or method is one which is implemented at class level.accessible from any class in the same package an any subclass anywhere While the above specifiers apply to the variables and the methods of a class.access from any class anywhere private .the class is visible from any class. which extends the class javax. inherited).servlet.HttpServlet and which implements the Serializable interface. has the same value for all class instances. A final: • • • variable . rather than at class instance.the default value allows access from any class in the same package public .servlet. Static variables and methods can be referenced (invoked) using either the name of the class or the name of a class instance. The declaration: abstract class myFirstClass extends javax. 34 .the class is abstract (some of its methods (inherited or specified by some interface) are to be implemented by some of its subclasses) An example.no access from outside the class itself protected .does not have any subclasses..
programmer defined exceptions 4. All exceptions (even programmer defined) must inherit from the standard class Throwable. Linkage Error and VirtualMachineError.4 . as defined in the java. Exception categories: 1.7.4 Handling Exceptions There are 2 ways to deal with exceptions: 35 . java errors . 4. The subclasses of the RuntimeException class. 2.ThreadDeath. Therte are 3 direct subclasses of the class Error .like invalid cast.7 exceptions in java An exception signals an abnormal situation or an error in an application. due to a variety of execution factors or due to programming errors. 4.JAVA PRIMER 4. namely class Error and the class Exception.7. all then exceptions in this category must be caught in our code.lang package are: • • • • • • • • • • • ArithmeticException IndexOutOfBoundException NegativeArraySizeException NullPointerException ArrayStoreException ClassCastException IllegalArgumentException SecurityException IllegalMonitorStateException IllegalStateException UnsupportedOperationException 4.7. In Java. division by 0. standard method exceptions 3. these exceptions take place because of serious code errors and they are supposed to be fixed in the coding phase.3 RuntimeException Exceptions Usually. not at execution time. code or data errors .1 The Error class Represent conditions which are not expected to be caught in our code. array index out of bounds. 4. All the standard exceptions are derived from 2 direct subclasses of Throwable. an exception is an object which is created when the abnormal situation occurs.7.2 The Exception class Except for the RuntimeException exceptions.JVM execution errors (mostly caused by programming errors).
security 36 . The name of the package is directly linked to the directory structure in which it is stored..io java.net java. is a subdirectory of a directory called bank11).lang (automatically available). In the example above. followed by the import statements. they have to be unique inside a package.class file.support for data collections.bank11. date and time info java. string analyzers. 4.rmi java. An example: package com. import.ccards.by adding the key word throws. 4.8.sql.java.util . import javax.4 . catch..support for java archives creation java.default.*.awt. followed by a comma separated list of exceptions after the parameter list of the method. . ignore it (pass it to the code that called the method) .sql java.support for event handling java.awt.Properties.lang . rather) defined in the java source must be stored in a directory called servlets. the default package is used). All other packages must be explicitly imported.awt . The package containing the standard classes is java. As a general rule.support for operations with 2D geometric figures java.JAVA PRIMER • • supply then code to deal with the exception inside the method .support for user interface java.util.1 Package names The default package has no name. don't have to import java.9 standard Java packages • • • • • • • • • • • • java. The names in a package are qualified by the package name.util.servlets.nio java.geom . the package statement is the first one in a java source file.this can be done by providing a try. Each class belongs to a package (even if a package name is not specified. the class (the . therefore.event . 4. finally construct. which is a subdirectory of ccards (which itself.8 java packages A Java package is a named collection of classes.zip .
swing GUI components (minimal dependence on native code) java.support for event handling 4. All methods declared in an interface are (by default) public and abstract.swing . If a class is declared as implementing an interface but omits some of its methods. While multiple inheritance is forbidden in Java (a class can be the subclass of a single base class). 37 . it must be declared as abstract. constants) of an interface are automatically (by default) public.accessibility javax.4 .JAVA PRIMER • • • • java.text javax.swing.10 interfaces An interface in Java corresponds to the abstract class concept in C++.event . Java classes can implement zero or more interfaces. static and final. An interface is a collection of constants and "abstract" functions. All variables (actually.
3 using an external JavaScript Sometimes you might want to run the same JavaScript on several pages. you can write a JavaScript in an external file... point to the .3. Note: The external script cannot contain the <script> tag! To use the external script.js"> </script> </head> <body> </body> </html> 5. Save the external JavaScript file with a .2 scripts in the body section Scripts which are to be executed when the page loads go in the body section.4 javaScript variables and expressions A variable is a "container" for some information whose value can change during the script. without having to write the same script on every page. you will ensure that the script is loaded before anyone uses it. Here is an example: <html> <head> <script type="text/javascript"> . When you place a script in the body section it generates the content of the page. <html> <head> </head> <body> <script type="text/javascript"> .3.3. </script> </head> 5.. To simplify this.js file in the "src" attribute of the <script> tag: <html> <head> <script src="myScript... or when an event is triggered.js file extension.5 . 5. go in the head section.1 scripts in the head section Scripts to be executed when they are called. 39 .javaScript times when a user triggers an event. When you place a script in the head section.. </script> </body> 5.
. 5.5 javaScript flow control Apart from the usual flow control constructs. break. switch(). for()..4..5 . while() it is worth mentioning the for .in statement is used to loop (iterate) through the elements of an array or through the properties of an object.4. 5.. else..2 variable declaration A variable can be declared or even created with the var statement: var strnum = "2157 Sunrise Blvd".5..3 variable assignment A value can be assigned to a variable at declaration time: var strnum = "Morii 771" Or just use a plain assignment: strname = "Morii 771" 5... The type of the variable is determined by any assignment of a value to that variable. This means that the type of the variable can change during the execution of a JavaScript script. The code in the body of the for .1 variable names Rules for variable names: • • Variable names are case sensitive They must begin with a letter or the underscore character 5.In statement The for. 5. namely – if . Syntax for (variable in object) { code to be executed } 40 .4. or strnum = "2157 Sunrise Blvd"..javaScript 5. catch constructs.4 variable types A variable declaration in JavaScript does not contain a type declaration. while()...1 JavaScript for..4. in and the try . continue. in loop is executed once for each element/property.
an array element.3 try. for (x in mycars) { document.5 . This chapter will teach you how to trap and handle JavaScript error messages.2 catching errors When browsing Web pages on the internet.0....5. When users see errors. This is the old standard solution to catch errors (available since Netscape 3) 5.javaScript The variable argument can be a named variable. } </script> </body> </html> 5. There are two ways of catching errors in a Web page: • • By using the try.. Mozilla 1. Error message like this may be useful for developers but not for users..write(mycars[x] + "<br />"). we all have seen a JavaScript alert box telling us there is a runtime error and asking "Do you wish to debug?".catch statement allows you to test a block of code for errors. Example Using for. The try block contains the code to be run. Syntax try { // run some code here } catch(err) { 41 . so you don't lose your audience.. mycars[0] = "Saab". they often leave the Web page. and Netscape 6) By using the onerror event...in to loop through an array: <html> <body> <script type="text/javascript"> var x.catch statement (available in IE5+. or a property of an object. mycars[1] = "Volvo".catch statement The try. and the catch block contains the code to be executed if an error occurs. var mycars = new Array().5. mycars[2] = "BMW".
6 operators The only new one is the comparison operator === (equal values and same type). } } </script> </head> <body> <input type="button" value="View message" onclick="message()" /> </body> </html> 5. When an alert box pops up. txt+="Error description: " + err.javaScript // handle errors here } Example <html> <head> <script type="text/javascript"> var txt="" function message() { try { adddlert("Welcome guest!"). Also. txt+="Click OK to continue. strings can be added (concateneted) using the + operator. 5.\n\n".5 . Syntax: 42 .7.\n\n". alert(txt). the user will have to click "OK" to proceed.7 popup boxes 5.1 alert Box An alert box is often used if you want to make sure information comes through to the user. } catch(err) { txt="There was an error on this page.description + "\n\n".
in the example above had not been written within a function.javaScript alert("sometext") 5. Now.2 confirm Box A confirm box is often used if you want the user to verify or accept something. If the user clicks "OK" the box returns the input value.js file)."defaultvalue") 5. If the user clicks "Cancel".5 . The syntax for creating a function is: 43 . If the user clicks "Cancel". the user will have to click either "OK" or "Cancel" to proceed after entering an input value.7.7. We have added an onClick event to the button that will execute the function displaymessage() when the button is clicked.. Syntax: prompt("sometext". the user will have to click either "OK" or "Cancel" to proceed. the box returns true.8 functions 5. the box returns null. Syntax: confirm("sometext") 5.3 prompt Box A prompt box is often used if you want the user to input a value before entering a page. When a confirm box pops up. the script is not executed before the user hits the button. A function can be called from anywhere within the page (or even from other pages if the function is embedded in an external . If the user clicks "OK". When a prompt box pops up. the box returns false. Functions are defined at the beginning of a page. in the <head> section. Example: <html> <head> <script type="text/javascript"> function displaymessage() { alert("Hello World!") } </script> </head> <body> <form> <input type="button" value="Click me!" onclick="displaymessage()" > </form> </body> </html> If the line: alert("Hello world!!"). it would have been executed as soon as the line was loaded.1 function definition A function contains some code that will be executed only by an event or by a call to that function.8.
length).1 object oriented programming JavaScript is an Object Oriented Programming (OOP) language.b) { x=a*b return x } When you call the function above. An OOP language allows you to define your own objects and make your own variable types.javaScript function functionname(var1. 5.2 the return statement The return statement is used to specify the value that is returned from the function.write(txt.3) The returned value from the prod() function is 6. var2.9 javaScript objects 5.9.varX) { some code } var1. 5.var2. So...2 properties Properties are the values associated with an object. you must pass along two parameters: product=prod(2. An example is the function below should return the product of two numbers (a and b): function prod(a. 5. etc are variables or values passed into the function.9. and will be stored in the variable called product. The next pages will explain each built-in JavaScript object in detail. function functionname() { some code } Note: Do not forget about the importance of capitals in JavaScript! The word function must be written in lowercase letters. functions that are going to return a value must use the return statement.8. and how they are used. </script> The output of the code above will be: 12 44 . otherwise a JavaScript error occurs! Also note that you must call a function with the exact same capitals as in the function name. The { and the } defines the start and end of the function. document.. In the following example we are using the length property of the String object to return the number of characters in a string: <script type="text/javascript"> var txt="Hello World!".5 .. We will start by looking at the built-in JavaScript objects.
N: Netscape. from a start index Extracts the characters in a string between two specified indices Displays a string as superscript Displays a string in lowercase letters Displays a string in uppercase letters Represents the source code of an object Returns the primitive value of a String object 1 1 1 2 2 2 3 3 3 link() match() replace() search() slice() small() split() strike() sub() substr() substring() sup() toLowerCase() toUpperCase() toSource() valueOf() 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 4 4 4 4 2 4 2 2 4 2 2 2 2 4 2 3 4 4 4 4 3 4 3 3 4 3 3 3 3 4 5. Properties FF: Firefox.5 . IE: Internet Explorer Property constructor prototype Methods Method Date() Description Returns today's date and time F F 1 N 2 I E 3 Description Returns a reference to the Date function that created the object Allows you to add properties and methods to the object F F 1 1 N 4 3 I E 4 4 47 . searching backwards from the specified position in a string Displays a string as a hyperlink Searches for a specified value in a string Replaces some characters with some other characters in a string Searches a string for a specified value Extracts a part of a string and returns the extracted part in a new string Displays a string in a small font Splits a string into an array of strings Displays a string with a strikethrough Displays a string as subscript Extracts a specified number of characters in a string.2 the Date object The JavaScript Date object is used to work with dates and times.11.javaScript indexOf() italics() lastIndexOf() Returns the position of the first occurrence of a specified string value in a string Displays a string in italic Returns the position of the last occurrence of a specified string value.
IE: Internet Explorer Property Description F F N I E 49 . to a string. according to local time. Properties FF: Firefox. to a string and returns the time portion Converts a Date object. according to local time. to a string Takes a date and returns the number of milliseconds since midnight of January 1. Use toUTCString() instead !! Converts a Date object. 1970 according to universal time Returns the primitive value of a Date object 1 1 4 2 4 3 1 1 1 1 1 1 2 4 4 2 4 2 3 4 4 3 4 1 1 1 1 1 1 1 1 4 4 4 4 4 4 4 2 4 4 4 4 4 4 4 3 valueOf() 1 2 4 5.5 . to a string Represents the source code of an object Converts a Date object to a string Returns the time portion of a Date object in readable form Converts a Date object.11. Use setFullYear() instead !! Returns the date portion of a Date object in readable form Converts a Date object. N: Netscape. according to local time.javaScript setUTCDate() setUTCMonth() setUTCFullYear() setUTCHours() setUTCMinutes() setUTCSeconds() setUTCMilliseconds() setYear() toDateString() toGMTString() toLocaleDateString() toLocaleTimeString() toLocaleString() toSource() toString() toTimeString() toUTCString() UTC() Sets the day of the month in a Date object according to universal time (from 1-31) Sets the month in a Date object according to universal time (from 0-11) Sets the year in a Date object according to universal time (four digits) Sets the hour in a Date object according to universal time (from 0-23) Set the minutes in a Date object according to universal time (from 0-59) Set the seconds in a Date object according to universal time (from 0-59) Sets the milliseconds in a Date object according to universal time (from 0-999) Sets the year in the Date object (two or four digits). according to Greenwich time. to a string and returns the date portion Converts a Date object.3 the Array object The JavaScript Array object is used to store a set of values in a single variable name. according to universal time.
Properties FF: Firefox.11.javaScript constructor index input length prototype Methods Method concat() join() pop() push() reverse() shift() slice() sort() splice() toSource() toString() unshift() valueOf() Description F Joins two or more arrays and returns the result Puts all the elements of an array into a string. Syntax for creating a new Number object.5 4 .5 4 3 4 .5 4 3 4 2 4 6 4 4 4 5 4 5 5 F N E 4 4 5 I Sets or returns the number of elements in an array Allows you to add properties and methods to the object Returns a reference to the array function that created the object 1 1 1 1 1 2 3 3 2 2 4 4 4 4 4 5. The elements are separated by a specified delimiter Removes and returns the last element of an array Adds one or more elements to the end of an array and returns the new length Reverses the order of the elements in an array Removes and returns the first element of an array Returns selected elements from an existing array Sorts the elements of an array Removes and adds new elements to an array Represents the source code of an object Converts an array to a string and returns the result Adds one or more elements to the beginning of an array and returns the new length Returns the primitive value of an Array object 1 1 1 1 1 1 1 1 1 1 1 1 1 4 3 4 .5 3 4 . IE: Internet Explorer Property constructor Description Returns a reference to the Number function that created the object F F 1 E 4 I 50 . var myNum=new Number(number).5 .4 the Number object The Number object is an object wrapper for primitive numeric values.
N: Netscape.5 1 .11.javaScript MAX_VALUE MIN_VALUE NaN NEGATIVE_INFINIT Y POSITIVE_INFINITY prototype Methods Method toExponential() toFixed() toLocaleString() toPrecision() toString() valueOf() Converts a number into an exponential notation if it has more digits than specified Converts the Number object into a string Returns the value of the Number object 1 .5 5 F E 5 I Represents a value that is greater than MAX_VALUE Allows you to add properties and methods to the object 1 1 4 4 Returns the largest possible value in JavaScript Returns the smallest possible value in JavaScript Represents "Not-a-number" value Represents a value that is less than MIN_VALUE 1 1 1 1 4 4 4 4 5.5 the Boolean object The JavaScript Boolean object is an object wrapper for a Boolean value.5 1 1 4 4 5 Description F Converts the value of the object into an exponential notation Formats a number to the specified number of decimals 1 . Properties FF: Firefox.5 . IE: Internet Explorer Property constructor prototype Methods Method toSource() toString() valueOf() Description F Returns the source code of the object Converts a Boolean value to a string and returns the result Returns the primitive value of a Boolean object 1 1 1 4 4 4 F N E 4 4 I Description Returns a reference to the Boolean function that created the object Allows you to add properties and methods to the object F F 1 1 N 2 2 I E 4 4 51 .
414) F F 1 1 1 1 1 1 1 1 N E I 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 52 . 2.442) Returns the base-10 logarithm of E (approx.718) Returns the natural logarithm of 2 (approx. 2.x) ceil(x) cos(x) exp(x) floor(x) log(x) max(x.javaScript 5. Properties FF: Firefox. 0. 1.14159) Returns the square root of 1/2 (approx.y) pow(x. It includes several mathematical constants and functions. IE: Internet Explorer Property E LN2 LN10 LOG2E LOG10E PI SQRT1_2 SQRT2 Methods Method abs(x) acos(x) asin(x) atan(x) atan2(y. 1. N: Netscape.302) Returns the base-2 logarithm of E (approx.693) Returns the natural logarithm of 10 (approx.y) random() round(x) sin(x) sqrt(x) tan(x) Description F Returns the absolute value of a number Returns the arccosine of a number Returns the arcsine of a number Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians Returns the angle theta of an (x.y) point as a numeric value between -PI and PI radians Returns the value of a number rounded upwards to the nearest integer Returns the cosine of a number Returns the value of Ex Returns the value of a number rounded downwards to the nearest integer Returns the natural logarithm (base E) of a number Returns the number with the highest value of x and y Returns the number with the lowest value of x and y Returns the value of x to the power of y Returns a random number between 0 and 1 Rounds a number to the nearest integer Returns the sine of a number Returns the square root of a number Returns the tangent of an angle 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 F N I E 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 Description Returns Euler's constant (approx.11.6 the Math Object The JavaScript Math object allows you to perform common mathematical tasks.707) Returns the square root of 2 (approx.y) min(x. 3. 0.434) Returns PI (approx. 0.5 .
age. play(). work(). but the values of those properties will differ from person to person.methodName() There are different ways to create a new object: 5. personObj.5 . personObj.propName You can add properties to an object by simply giving it a value.12. etc.12 how to create your own objects An object is just a special kind of data.lastname="Doe".javaScript toSource() valueOf() Represents the source code of an object Returns the primitive value of a Math object 1 1 4 2 4 5. 53 .1 Properties The syntax for accessing a property of an object is: objName.12.firstname="John". lastname.you can give it properties named firstname. Let's illustrate with an example: A person is an object. Methods are the actions that can be performed on objects. sleep(). Assume that the personObj already exists . All persons have these properties.eyecolor="blue".firstname="John". with a collection of properties and methods.age=50. personObj. personObj. Properties are the values associated with the object. The persons' properties include name.firstname).write(personObj. 5. age.lastname="Doe".2 Methods An object can also contain methods.eyecolor="blue". eye color. You can call a method with the following syntax: objName. personObj. weight.3 create a direct instance of an object The following code creates an instance of an object and adds four properties to it: personObj=new Object(). personObj. and eyecolor as follows: personObj. Objects also have methods. The persons' methods could be eat(). height.age=30. skin tone. etc. personObj.12. document. The code above will generate the following output: John 5.
The following code adds a method called eat() to the personObj: personObj. this. myMother=new person("Sally".newlastname=newlastname.lastname.age=age. this. The reason for all the "this" stuff is that you're going to have more than one person at a time (which person you're dealing with must be clear). That's what "this" is: the instance of the object at hand. Once you have the template."green"). this.eyecolor=eyecolor.48."blue").eyecolor=eyecolor.javaScript Adding a method to the personObj is also simple.12. Inside the function you need to assign things to this.lastname=lastname.propertyName.eyecolor) { this. like this: myFather=new person("John"."Doe".eyecolor) { this."Rally".age. this. } Notice that the template is just a function.age=age. you can create new instances of the object. 54 .50.firstname=firstname. this. You can also add some methods to the person object.4 create a template of an object The template defines the structure of an object: function person(firstname.lastname.firstname=firstname.age.eat=eat. 5. Then we will have to write the newlastname() function: function newlastname(new_lastname) { this. This is also done inside the template: function person(firstname.lastname=new_lastname.5 .lastname=lastname. } Note that methods are just functions attached to objects. this. this.
gif" width="100" height="30"> </a> 57 .javaScript event').return false"> <img src="w3schools.5 .
a new DOM Core specification. 4. DOM Level 3 Requirements. and potentially any errata on older DOM specifications. which existed before the creation of DOM Level 1. DOM Level 3 Views and Formatting. As of 2005. DOM Level 3 XPath. and 6. DOM Level 3 Load and Save. Examples include the DHTML Object Model or the Netscape intermediate DOM.3 levels The W3C DOM specifications are divided into levels. Level 0 is not a formal specification published by the W3C but rather a shorthand that refers to what existed before the standardization process. DOM Level 3 Core. 3. which further enhances the DOM 6. 2. filtered views and events.Html DOM Web Applications Working Group has taken over responsibility for the Document Object Model specifications. An application may also support vendor-specific extensions which don't conflict with the W3C standards.6 . Level 2. Level 3 Consists of 6 different specifications: 1. Level 1 Navigation of DOM (HTML and XML) document (tree structure) and content manipulation (includes adding elements). and some modules of Level 3 are W3C Recommendations which means they have reached their final form. HTML-specific elements are included as well. Level 2 XML namespace support. Level 1. including a new revision of DOM Level 3 Events. an application must implement all the requirements of the claimed level and the levels below it. Level 0 The application supports an intermediate DOM. 6. 5. DOM Level 3 Validation. each of which contains required and optional modules. To claim to support a level.4 specifications • • • Document Object Model (DOM) Level 1 Specification Level 2 Recommendations: • Document Object Model (DOM) Level 2 Core Specification • Document Object Model (DOM) Level 2 Views Specification • Document Object Model (DOM) Level 2 Events Specification • Document Object Model (DOM) Level 2 Style Specification • Document Object Model (DOM) Level 2 Traversal and Range Specification • Document Object Model (DOM) Level 2 HTML Specification Level 3 Recommendations: • Document Object Model (DOM) Level 3 Core Specification 59 .
The HTML DOM is platform and language independent. It can be used by any programming language like Java.6 . HTML DOM Objects Object Document Anchor Area Base Body Button Event Form Frame Frameset Iframe Image Input button Input checkbox Input file Input hidden Input password Input radio Input reset Input submit Input text Link Meta Option Select Style Table TableData TableRow Textarea Description Represents the entire HTML document and can be used to access all elements in a page Represents an <a> element Represents an <area> element inside an image-map Represents a <base> element (specifies a default address or a default target for all links on a page) Represents the <body> element Represents a <button> element Represents the state of an event Represents a <form> element Represents a <frame> element Represents a <frameset> element Represents an <iframe> element Represents an <img> element Represents a button in an HTML form Represents a checkbox in an HTML form Represents a fileupload in an HTML form Represents a hidden field in an HTML form Represents a password field in an HTML form Represents a radio button in an HTML form Represents a reset button in an HTML form Represents a submit button in an HTML form Represents a text-input field in an HTML form Represents a <link> element Represents a <meta> element Represents an <option> element Represents a selection list in an HTML form Represents an individual style statement Represents a <table> element Represents a <td> element Represents a <tr> element Represents a <textarea> element 61 . JavaScript.Html DOM DOM. and VBScript. The contents can be modified or deleted. and new elements can be created.
the element node <title>.8. The <html> node has two child nodes. All other nodes in the document are contained within <html>. the text of an element node is stored in a text node. The tree structure is called a node-tree. "DOM Tutorial" is not the value of the <title> element! However. The <body> node holds a <h1> and <p> node. 62 . everything in an HTML document is a node. The <head> node holds a <title> node.2 text is always stored in text nodes A common error in DOM processing is to expect an element node to contain text.9. The DOM says: • • • • • The entire document is a document node Every HTML tag is an element node The text in the HTML elements are text nodes Every HTML attribute is an attribute node Comments are comment nodes 6. 6. <head> and <body>.Html DOM 6. However. In this example: <title>DOM Tutorial</title>. 6.1 DOM example Look at the following HTML document: <html> <head> <title>DOM Tutorial</title> </head> <body> <h1>DOM Lesson one</h1> <p>Hello world!</p> </body> </html> The root node in the HTML above is <html>. in the HTML DOM the value of the text node can be accessed by the innerHTML property.6 .9 the HTML DOM Node Tree 6.1 the Document Tree The HTML DOM views a HTML document as a tree-structure.8.8 DOM nodes According to the DOM. holds a text node with the value "DOM Tutorial".
Children on the same level are called siblings (brothers or sisters). The node tree below shows the set of nodes. The following example returns a nodeList of all <p> elements that are descendants of the element with id="main": document. using the node relationships.getElementById('main').9. You can loop through a node list by using the length property: x=document.2 node parents.Html DOM All nodes can be accessed through the tree.3 accessing nodes You can access a node in three ways: 1. has exactly one parent node A node can have any number of children A leaf is a node with no children Siblings are nodes with the same parent 6. By using the getElementsByTagName() method 3.getElementsByTagName("p"). and siblings The nodes in the node tree have a hierarchical relationship to each other. The length property defines the length of a node list (the number of nodes).getElementsByTagName("p"). The terms parent. • • • • • In a node tree. The tree starts at the root node and branches out to the text nodes at the lowest level of the tree: 6.9. except the root. 63 . By using the getElementById() method 2. Parent nodes have children. and new elements can be created. and sibling are used to describe the relationships. Their contents can be modified or deleted. the top node is called the root Every node. child. children. By navigating the node tree.6 . and the connections between them.
innerHTML). • • • • • nodeName is read-only nodeName of an element node is the same as the tag name nodeName of an attribute node is the attribute name nodeName of a text node is always #text nodeName of the document node is always #document the nodeValue Property The nodeValue property specifies the value of a node.6 .write(x[i].i<x.4 Node Properties In the HTML Document Object Model (DOM). Objects have methods (functions) and properties (information about the object).i++) { document. Three important HTML DOM node properties are: • • • nodeName nodeValue nodeType the nodeName Property The nodeName property specifies the name of a node.write("<br />").9. that can be accessed and manipulated by JavaScript. The most important node types are: Element type Element Attribute Text Comment Document NodeType 1 2 3 8 9 64 . document.Html DOM for (i=0. } 6.length. • • • nodeValue for element nodes is undefined nodeValue for text nodes is the text itself nodeValue for attribute nodes is the attribute value the nodeType Property The nodeType property returns the type of node and is read only. each node is an object.
firstChild.getElementById("intro"). Category Type Attribute Description Fires when the pointing device button is clicked over an element. The sequence of these events is: • mousedown • mouseup • click Fires when the pointing device button is double clicked over an element Fires when the pointing device button is pressed over an element Fires when the pointing device button is released over an element Fires when the pointing device is moved onto an element Fires when the pointing device is moved while it is over an element Fires when the pointing device is moved away from an element click onclick dblclick Mouse mousedown mouseup mouseover mousemove mouseout ondblclick onmousedown onmouseup onmouseover onmousemove onmouseout 65 .get the value of an element The following code fragment retrieves the text node value of the first <p> element: x=document.6 .nodeValue.5 example .9. A click is defined as a mousedown and mouseup over the same screen location.10 HTML events Common/W3C events There is a huge collection of events that can be generated by most element nodes: • • • • • • Mouse events Keyboard events HTML frame/object events HTML form events User interface events Mutation events (notification of any changes to the structure of a document) Note that the event classification above is not exactly the same as W3C's classification.Html DOM 6. txt=x. 6.
frames. but can be applied to any focusable element keypress Keyboard keydown keyup onkeypress onkeydown onkeyup load onload unload HTML frame/object abort onunload onabort error resize scroll select onerror onresize onscroll onselect change HTML form submit reset focus onchange onsubmit onreset onfocus blur User interface DOMFocusIn onblur ondomfocusin 66 . it fires when the target element and all of its content has finished loading Fires when the user agent removes all content from a window or frame. The sequence of these events is: • keydown • keyup • keypress Fires when a key on the keyboard is pressed Fires when a key on the keyboard is released Fires when the user agent finishes loading all content within a document. For elements. A keypress is defined as a keydown and keyup on the same key. For elements.6 .Html DOM Fires when a key on the keyboard is "clicked". objects and images. including window. including input and textarea Fires when a control loses the input focus and its value has been modified since gaining focus Fires when a form is submitted Fires when a form is reset Fires when an element receives focus either via the pointing device or by tab navigation Fires when an element loses focus either via the pointing device or by tabbing navigation Similar to HTML focus event. it fires when the target element or any of its content has been removed Fires when an object/image is stopped from loading before completely loaded Fires when an object/image/frame cannot be loaded properly Fires when a document view is resized Fires when a document view is scrolled Fires when a user selects some text in a text field.
Mozilla and Opera support DOMAttrModified. Fires when an element is activated. This model is implemented in Internet Explorer and other browsers. and/or by cancelling the default action for the event.11 event flow Consider the situation when there are 2 elements nested together.3. This model is implemented in Netscape Navigator. Also. 67 . as of version 1.stopPropagation() for Mozilla and command event.Html DOM DOMFocusOut ondomfocusout Similar to HTML blur event. Events are first captured until it reaches the target element. When the user clicks on the inner element. DOMNodeRemoved and DOMCharacterDataModified. but can be applied to any focusable element Similar to XUL command event. Safari and Opera also support readystatechange event for the XMLHttpRequest object. and then bubbled up. Trigger the elements from inner to outer (event bubbling). also supports these methods. Mozilla also supports the beforeunload event using traditional event registration method (DOM Level 0).cancelBubble = true for Internet Explorer). W3C takes a middle position in this struggle. through a mouse click or a keypress. there are two possible ways to handle it: • • Trigger the elements from outer to inner (event capturing). an event can be responded to at any element in the path (an observer) in either phase by causing an action. for instance. During the event flow. Safari. Both have event handlers registered on the same event type. Fire when the subtree is modified Fires when a node has been added as a child of another node Fires when a node has been removed from a DOM-tree DOMActivate ondomactivate DOMSubtreeModified DOMNodeInserted DOMNodeRemoved Mutation onsubtreemodified onnodeinserted onnoderemoved NodeInsertedIntoDoc onnodeinsertedinto Fires when a node is being ument document inserted into a document DOMAttrModified onattrmodified Fires when an attribute has been modified DOMCharacterDataM oncharacterdatamo Fires when the character data odified dified has been modified Note that the events whose names start with "DOM" are currently not well supported. but Internet Explorer for the Mac does not. 6. and/or by stopping the event (with method event.6 . DOMNodeInserted. Mozilla and Safari also support contextmenu. say "click". Mozilla.
Hence only the W3C Event object is discussed here. Used to indicate whether or not an event can have its default action prevented. meaning that any default action normally taken by the implementation as a result of the event will not occur. Unfortunately. Used to indicate which phase of event flow is currently being evaluated. including information about target element. Event properties Type DOMString EventTarget EventTarget unsigned short boolean boolean DOMTimeStamp Name type target currentTarget eventPhase bubbles cancelable timeStamp Description The name of the event (case-insensitive). Event methods Name stopPropagation Argument type Argument name Description To prevent further propagation of an event during event flow. Used to indicate the EventTarget whose EventListeners are currently being processed. Specifies whether or not the event's default action can be prevented. preventDefault 68 . key pressed. Used to indicate whether or not an event is a bubbling event. mouse position. Specifies whether or not the event can bubble.12 the Event object The Event object provides a lot of information about a particular event.Html DOM 6. DOMString initEvent boolean boolean eventTypeArg canBubbleArg cancelableArg Specifies the event type. there are very serious browser incompatibilities in this area.6 . mouse button pressed. etc. Used to indicate the EventTarget to which the event was originally dispatched. To cancel the event if it is cancelable. Used to specify the time (in milliseconds relative to the epoch) at which the event was created.
holds a Xml loaded file.responseXml . and in this purpose.holds loaded data as a string of characters. the state of availability of data is given by the readyState attribute of XMLHttpRequest.open: create a connection. 1: connection established. 3: answer in process. . We have to wait for the data to be available to process it. 4: finished. 2: request received. url.AJAX 7.returned by the server . To get data on the server. DOM's method allows to extract data.for a simple text. they call functions associated to elements of the web page.200 is ok.for a Xml file or . Data furnished by the server will be found in these attributes of the XMLHttpRequest object: . Attributes readyState status responseText responseXml . Take note that a new XMLHttpRequest object has to be created for each new file to load. These events are user actions.the code successively changes value from 0 to 4 that means "ready".mode: type of request. This object provides two methods: . thanks to its methods and attributes. . It allows the interaction with the servers.5 the XMLHttpRequest class Here is a closer look to the XMLHttpRequest class. Interactivity is achieved with forms and buttons.the name of the function invoked Methods open(mode. . the ajax engine uses the XMLHttpRequest object. States of readyState follow (only the last one is really useful): 0: not initialized. GET or POST . 7. 404 if the page is not found . onreadystatechange .responseText .4 how does it work? Ajax uses a programming model with display and events.send: send a request to the server. DOM allows to link elements of the page with actions and also to extract data from Xml files provided by the server. boolean) .url: the location of the file 72 .7 .
open('GET'. // IE } Second step: wait for the response The response and further processing are included in a function and the return of the function will be assigned to the onreadystatechange attribute of the object previously created..XMLHTTP").open: command GET or POST. if (window. if (request.xml'. } else if (window.send: with POST only.. The request below reads a document on the server. for browser compatibility.readyState == 4) { // received. // Firefox.fr/somefile. but two options must be tried.. URL of the document. step by step First step: create an instance This is just a classical instance of class.XMLHttpRequest) // Object of the current windows { request = new XMLHttpRequest(). true for asynchronous. http_request. OK } else { // wait.null for a GET command 7. http_request.onreadystatechange = function() { // instructions to process the response }. .AJAX .7 . Safari.boolean: true (asynchronous) / false (synchronous) send("string") . the data to send to the server. .xul.6 building a request. } Third step: make the request itself Two methods of XMLHttpRequest are used: . 'http://www. 73 .ActiveXObject) // ActiveX version { request = new ActiveXObject("Microsoft. request.send(null).. true).
7.ajax. }.responseText.status == 200) document.responseText.XMLHttpRequest) req = new XMLHttpRequest().7 .open("GET". // read the first element with a dom's method 74 . req.status.responseXML. req. } </script> </head> <body> <FORM method="POST" name="ajax" action=""> <INPUT type="BUTTON" value="Submit" ONCLICK="submitForm()"> <INPUT type="text" name="dyn" value=""> </FORM> </body> </html> 7. req.setRequestHeader("Content-Type". if(window.ActiveXObject) req = new ActiveXObject(Microsoft. true).dyn="Error code " + req.7 examples 7. "application/x-www-form-urlencoded").7. req.1 How to get a text <html> <head> <script> function submitForm() { var req = null.readyState == 4) if(req.dyn=""Received:" + req.XMLHTTP).AJAX 7.getElementsByTagName('root').xml".ajax.2 how to get from xml To get data from a xml file we have just to replace this line: document.dyn="Received:" + req. else if (window. by this code: var doc = req.ajax.onreadystatechange = function() { if(req.item(0). else document.send(null). "data. // assign the Xml file to a var var element = doc.
document.ajax.dyn.value= element.firstChild.data; content of the element to the form // assign the
7.7.3 how to post a text
A text is sent to the server and is written into a file. The call to the "open" method changes, the argument is POST, and the "send" method also has now a value for argument. req.open("POST", "ajax-post.xml", true); req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); req.send(document.getElementById("dyn".value));
7.7.4 how to write to body
Now, the text read is put in the body of the page, and not into a textfield. The code below replaces the textfield form object and the second part replaces the assignment into the JavaScript function. <div id="zone"> ... some text to replace ... </div> document.getElementById("zone").innerHTML = "Received:" + xhr.responseText;
7.8 the ajax toolkit framework
7.9 drawbacks of ajax
● ● ● ●
7.10 Specifications
Ajax is based on these specifications:
● ● ●
XML 1, HTML 4.0, DOM 2, from W3C ECMAScript 1.5 (standard for JavaScript) from ECMA W3C draft specification for XMLHttpRequest.
8.1 the structure of a web application
A web application is a collection of Java servlets, JSP pages, Java Server Faces, other helper classes and class libraries, other static resources (HTML, images, etc.) and an xml file, the deployment descriptor. A web application consists of 4 parts: 1. a public directory – containing html, jsp files and other public resources. This is the root directory of the application. 2. a WEB-INF/web.xml file – the deployment descriptor. 3. a WEB-INF/classes directory. 4. a WEB-INF/lib directory. Example: Assume that we use a Tomcat web server and that the environment variable %TOMCAT_HOME% is set to C:\TW\Tomcat. Then, the root directory of some web application can be: C:\TW\Tomcat\webapps\bank11\ccards and the mandatory directories are: C:\TW\Tomcat\webapps\bank11\ccards\WEB-INF\classes C:\TW\Tomcat\webapps\bank11\ccards\WEB-INF\lib
8.2 web containers
A web container is a Java runtime providing implementation of the Java servlet API and some other facilities to the JSP and JSF pages. It responsible for initializing, invoking and managing the life cycle of servlets, JSPs and JSFs. A web container may either implement the basic HTTP services or delegates these services to an external web server. Web containers can be part of an application or web server or a separate runtime. Here is a description of these situations. web container in a J2EE application server. Commercial implementations of the J2EE specifications, like WebLogic, Inprise Application Server or IBM's WebSphere include web containers. web container built into web servers. Most known cases are the Sun's (Oracle's) Java WebServer and the Jakarta Tomcat web server. web container as a separate runtime. Some web servers, like Apache or IIS require a separate runtime to run servlets and a web server plug-in to integrate this Java runtime
• •
with the web server. Typical integration scenarios are Tomcat with Apache and JRun (of Allaire) with most of the J2EE application servers.
Web Application
Web Application
Java Servlets
Java Servlets
JSP Pages
JSP Pages
JavaServer Faces
JavaServer Faces
Java Classes
Deployment descriptor
Deployment descriptor
Java EE Web Container
8.3 container services
Containers are the interface between a component and the low-level platform-specific functionality that supports the component. Before a web, enterprise bean, or application client component can be executed, it must be assembled into a Java EE module and deployed into its container. The assembly process involves specifying container settings for each component in the Java EE application and for the Java EE application itself. Container settings customize the underlying support provided by the Java EE server, including services such as security, transaction management, Java Naming and Directory Interface (JNDI) lookups, and remote connectivity. Here are some of the highlights:
The Java EE security model lets you configure a web component or enterprise bean so that system resources are accessed only by authorized users.
4. Here is a small. Servlet. like: 1. entries related to session configuration.servlets.. The Java EE remote connectivity model manages low-level communications between clients and enterprise beans. The deployment descriptor serves several purposes. 5.xml file: <?xml version="1. JSPs and Java Server Faces. application components within the same Java EE application can behave differently based on where they are deployed. JSPs and Java Server Faces definitions.LoginServlet </servlet-class> </servlet> </web-app> 79 . welcome pages.)> <web-app> <!-. Security related entries – may specify which pages require login and the roles different users may have. servlet classes. classes. 6.bank11. For example.class>com.xml) which allows the customization of the web application at deployment time. Servlet. web. descriptions). and access to the Java EE platform APIs.Define the Bank 11 ccards Servlets --> <servlet> <servlet-name>Login</servlet-name> <servlet. a client invokes methods on it as if it were in the same virtual machine.8 . Initialization of parameters for servlets. Others.ccards. After an enterprise bean is created. JNDI lookup services provide a unified interface to multiple naming and directory services in the enterprise so that application components can access these services. The container also manages nonconfigurable services such as enterprise bean and servlet life cycles. Because the Java EE architecture provides configurable services. JSPs and Java Server Faces mappings. MIME types used by the web application.WEB APPLICATIONS • • • The Java EE transaction model lets you specify relationships among methods that make up a single transaction so that all methods in one transaction are treated as a single unit.0" encoding="ISO-8859-1" ?> <!DOCTYPE web-app (View Source for full doctype. 8. 2.. data persistence. but typical web. precompiled JSP entities are declared (names. 3.4 deployment descriptor The deployment descriptor is an xml file (namely. database connection resource pooling. an enterprise bean can have security settings that allow it a certain level of access to database data in one production environment and another level of database access in another production environment. like what pages are error.
basicly. in an UNIX environment) is set to "C:\TW\Tomcat".class" and that it is part of the package "com. The "/Enroll" part of the URL identifies the servlet.5 practical deployment issues There are several issues with the web applications deployment. However.ccards. the location of the base directory of a web application may be any sub(sub)directory of "%TOMCAT_HOME%\webapps". The association between the name of the web application and the location of its base directory is made by a <context> element in the "%TOMCAT_HOME%\conf\server. then the corresponding <context> element in the "%TOMCAT_HOME%\conf\server.bank11.servlets". The "/servlet" part of the URL tells the web server (Tomcat. 1. if the base directory of the "/ccards" web application is "%TOMCAT_HOME %\webapps\vdumitrascu\cc". it is the alias of the real servlet class. The "/ccards" part of the URL is.xml file of the web application. This subdirectory has (in general) the same name as the application itself.servlets". the lines which deal with this issue are commented out in the latest version of Tomcat (for so-called "security issues"). This association is made in the file "%TOMCAT_HOME%\conf\web.xml" 2.bank11. More exactly the corresponding <servlet> element should look like: <servlet> <servlet-name>Enroll</servlet-name> <servlet-class>com. For example. Then the "EnrollServlet. Assume that we work with Tomcat and that the environment variable %TOMCAT_HOME% (or $TOMCAT_HOME. To make anything work: • de-comment the following section: <servlet-mapping> <servlet-name>invoker</servlet-name> <url-pattern>/servlet/*</url-pattern> </servlet-mapping> in the configuration file "%TOMCAT_HOME%\conf\web.xml" file looks like: <context path="/ccards" docbase="vdumitrascu/cc" /> 3.bank11. Basicly. Let's say that this class is "EnrollServlet.ccards.xml" file. This association between the (short) alias of the servlet and its real (long) name is made in the web.class" file must be located in the directory "%TOMCAT_HOME%\webapps\vdumitrascu\cc\WEBINF\classes\com. the name of the web application.EnrollServlet </servlet-class> </servlet> 80 . like "http://localhost:8080/ccards/servlet/Enroll" there are 3 things which have to be fixed in order to make things work properly. Behind a very benign URL. the base directory of an application is a subdirectory of the "%TOMCAT_HOME%\webapps" directory. for flexibility.8 .xml".ccards. Unfortunately.WEB APPLICATIONS 8. in our case) to execute the invoker servlet. In general. whose name is rather long.servlets.
0 specification is available for public review. tjws spec 2. this is just a work in progress. Technically speaking. The servlet lives within this container which provides an execution environment for the servlet class.4. As of oct. Java EE 6 SDK is intended to contain an implementation of the Java Servlet 3. the HttpServlet) class. but at this point.2 servlet containers The servlet does not communicate directly with the client. 2010. a servlet is a Java class that extends the GenericServlet (or. Web containers are implemented by various vendors.SERVLETS 9. from Sun Microsystems (Oracle) JBoss (open source) JRun. but through a web container. which extend the functionality of the web server.2 commercial servlet containers • • • • • • • BEA WebLogic Server or Weblogic Express.2. small footprint. Jetty Jaminid contains a higher abstraction than servlets.5 and is in final state. more often.9 . 9. in most cases as part of an application server. from BEA Systems. from Adobe Systems (formerly developed by Allaire Corporation) 81 . the Java Servlet 3. modular design 9. The Java Servlet API provides a simple frame for building web applications on web servers. Apache Geronimo is a full Java EE implementation by Apache.1 the servlets as part of web applications Java servlets – small. maintained by Oracle Java System Application Server . 9. Enhydra Winstone supports specification 2. has a focus on minimal configuration and the ability to strip the container down to only what you need. from Sun Microsystems (Oracle) Java System Web Server . platform independent programs.0 specification.4.2. now bought by Oracle Borland Enterprise Server GlassFish (open source).SERVLETS 9 .1 Noncommercial servlet containers • • • • • • • Apache Tomcat (formerly Jakarta Tomcat) is an open source web container available under the Apache Software License. The current Java Servlet specification is 2.
servlet. public void destroy() throws ServletException. from New Atlanta Communications WebObjects. public void service(ServletRequest req.3 servlet packages and classes The Java servlet API consists of 2 packages. the javax. The classes and interfaces of the Java servlet API can be divided in several categories. from IBM 9.servlet package.servlet javax. ServletResponse resp) throws ServletException. WebSphere. These packages are: • • javax. which are part of the Java Platform SDK. namely: • • • • • • • • servlet implementation servlet configuration servlet exceptions request and responses session tracking servlet context servlet collaboration miscellaneous 9.servlet. from Oracle Corporation Orion Application Server . It declares the following methods: public void init(ServletConfig config) throws ServletException. from Apple Inc.9 .http contains classes and interfaces which are HTTP specific. Enterprise Edition.SERVLETS • • • • • • • LiteWebServer (open source) Oracle Application Server . while the second one. from IronFlare Caucho's Resin Server ServletExec .servlet package are protocol independent.http The classes and interfaces defined in the javax. IOException. 82 . public ServletConfig getServletConfig().4 the Servlet interface The Servlet interface is part of the javax.
Methods specific to this class: public void init() public void log(String msg) public void log(String msg.5 the GenericServlet class public abstract class GenericServlet implements Servlet. After instantiating the servlet. ServletConfig. namely the HttpServlet class. The web container calls the service() method in response to any incoming request. Throwable t) 9. HttpServletResponse resp) protected void doPost(HttpServletRequest req. All classes extending the GenericServlet class should provide an implementation for the service() method. the web container calls its init() method. before the servlet processes any HTTP request. HttpServletResponse resp) protected void doGet(HttpServletRequest req. ServletResponse resp) public void service(HttpServletRequest req. More on the servlet life cycle. 83 . respectively. in a different section. arguments which implement the ServletRequest and ServletResponse interfaces. without having to obtain a ServletConfig object first. The method performs all initialization required. Since this class implements the ServletConfig interface. public abstract class HttpServlet extends GenericServlet implements Serializable The HttpServlet provides an HTTP specific implementation of the Servlet interface. This method has two arguments. The servlet specification insures that the init() method is called just once for any given instance of the servlet. 9. Serializable This class provides a basic implementation of the Servlet interface.6 the HttpServlet class It is very likely that the only implementation of the Servlet interface we'll ever use is one that processes an HTTP request.9 . as well. the developer may call ServletConfig methods directly. The servlet API provides such a specific class. This abstract class specifies the following methods: public void service(ServletRequest req.SERVLETS public String getServletInfo().
doXXX() and destroy() methods of the Servlet interface implementations. HttpServletResponse resp) 9.lang.servlet. 9.8 servlet exceptions The Java servlet API specifies two servlet specific exceptions: javax. HttpServletResponse resp) protected void doPut(HttpServletRequest req.SERVLETS HttpServletResponse resp) protected void doDelete(HttpServletRequest req. a servlet instance goes through the following stages: 84 .ServletException javax. HttpServletResponse resp) protected void doOptions(HttpServletRequest req. containing web container information This interface specifies the following methods: public public public public String getInitParameter(String name) Enumeration getInitParameterNames() ServletContext getServletContext() String getServletName() 9. The UnavailableException indicates to the web container that the servlet instance is unavaialble.lang. service().9 the servlet lifecycle Generally.UnavailableException The ServletException class extends java. HttpServletResponse resp) protected void doTrace(HttpServletRequest req.9 .7 the ServletConfig interface This interface abstracts configuration information about the servlet. namely: • • • initialization parameters (as name-value pairs) the name of the servlet a ServletContext object. It also extends the java.Exception and can be thrown by the init().Exception class.servlet.
There are 3 different ways for attaching and retrieving attributes. which requires that the service() method be thread safe. But what is the difference between a parameter and an attribute? While the parameters of the request are part of the request itself. Typically. the container calls the init() method of the servlet.SingleThreadModel. DB connection opening. Object attr) Enumeration getAttributeNames() int getContentLength() String getContentType() String getParameter(String name) Enumeration getParameterNames() String[] getParameterValues() String getServerName() int getServerPort() String getRemoteAddr() String getRemoteHost() Most of the above methods are self explanatory. Typically. method which performs the initialization of the servlet. or to allow sending data from a servlet to another. The purpose of attributes is to allow the container to provide additional data to a servlet. the attributes of the request are attached by the web containers or by the servlets/JSPs/JSFs. concurrent requests are serviced in more than one service thread. 85 . respectively. which will service all incoming requests. JSP or JSF. 9.SERVLETS • • • • • instantiation initialization service destroy unavailable The container creates a servlet instance as first response to an incoming (HTTP) request or at container startup. If the servlet does not implement the javax. The other two use the HttpSession and ServletContext objects. etc. the web container creates a single instance of the servlet. the servlet's destroy() method will be called before the servlet itself is destroyed. After instantiation. The first one is to attach attributes to the request object. The web container makes sure that the init() method of the servlet will be completed before invoking its service() method. this method contains JDBC driver loading.10 the ServletRequest interface Here are some of the methods of this interface: public public public public public public public public public public public public Object getAttribute(String name) Object setAttribute(String name.servlet.9 . Also.
Here are the most important ones: public ServletOutputStream getOutputStream() public PrintWriter getWriter() public void setContentLength(int len) public void setContentType(String type) public void setBufferSize(int size) public int getBufferSize() public void flushBuffer() 9.11 the HttpServletRequest interface public interface HttpServletRequest extends ServletRequest This interface contains HTTP specific methods.12 the ServletResponse interface This interface defines methods for constructing responses to servlet requests.13 the HttpServletResponse interface This interface extends the ServletResponse interface and defines methods specific for constructing responses to HTTP requests. Here are some of them: public Cookie[] getCookies() public long getDateHeader() public String getHeader(String name) public Enumeration getHeaders(String name) public Enumeration getHeaderNames() public String getContextPath() public String getPathInfo() public String getQueryString() public String getRemoteUser() 9.9 . One has to take in account the structure of an HTTP request when overviewing the most important methods of this interface. Here are the most important ones: 86 .SERVLETS 9.
87 .bank11.html) Here is its abbreviated form (topics which are DB related are postponed) of the "EnrollServlet. String message) public void setHeader(String headerName. public String getMIMEType(String fileName) public String getResource(String path) public ServletContext getContext(String urlPath) public String getInitParameter(String name) public Enumeration getInitParameterNames() public Object getAttribute(String name) public Enumeration getAttributeNames() public void setAttribute(String name. import java. Object attr) public String removeAttribute(String name) 9.*.14 the ServletContext interface A servlet context defines servlet's view of the web application and provides access to resources common to all servlets of the web application.xml file. This is done in server's (container's) server. String value) public void setStatus(int statusCode) 9.io.java" file: package com.servlets. A reference to an object of this type can be obtained by invoking the getServletContext() method of the HttpServlet object. The deployment of a web application involves adding an application specific <context> tag which associates the the name of the application with its root directory.SERVLETS public void addCookie(Cookie cookie) public String encodeURL(String url) public void sendError(int status) public void sendError(int status. String value) public void addHeader(String headerName.9 .ccards.15 the Enroll servlet The Enroll servlet services the request sent by the web browser when we submit the Enroll form (file Enroll. Each servlet context is rooted at a specific path in the web server. The ServletContext interface abstracts the context of a web application.
getWriter().*.servlet. } public void doPost(HttpServletRequest req. HttpServletResponse resp) throws ServletException.close(). out.http. out.println("</body>"). out.println("<html>").println("merge"). import javax.SERVLETS import javax.println("</html>").init(config).println("<head>"). PrintWriter out = resp. out. out.println("<br>"). // output your page here out.servlet. public class EnrollServlet extends HttpServlet { public void init(ServletConfig config) throws ServletException { super.println("</head>"). } } 88 .9 .setContentType("text/html"). out.*. IOException { resp. out. out.println("<body>"). out.println("<title>Servlet</title>").
JDBC 10 .JdbcOdbcDriver .2 jdbc drivers Each database vendor offers its own version of DB access API. JDBC evolution is part of the Java Community Process.odbc. It abstracts the vendor-specific details and offers support for the most common database access functions. The standard JDK includes all classes for this bridge .1 what is jdbc? JDBC stands for Java Data Base Connectivity and is the Java version of ODBC (Open Data Base Connectivity).sql package 2. 89 . as recognized by the DB industry. Both the JDBC and the JDBCODBC calls are invoked within the client application.1. Starting with version 3. 10.sun.10 . the javax. due to the multiple layers of indirection involved and to the limitations imposed to the JDBC layer by the ODBC frame. This solution is inefficient.sql package. The JDBC 4. which provides several server-side capabilities The JDBC API provides programmatic access from applications written in the Java programming language to standard SQL. A JDBC driver is a middleware layer that translates JDBC calls into vendor specific calls.jdbc.0 while the current (4. The first release of the JDBC specification dates back to Feb. These drivers fall into four standard categories. the java. JSR (Java Specification Request) 54 defines JDBC 3.0. After that. It offers an API for SQL-compliant relational databases access.JDBC 10.0) JDBC specification is defined in JSR 221. JDBC was part of Java Standard Edition (JSE). as part of the Java Development Kit (JDK) 1. JDBC – ODBC Bridge The driver translates the JDBC calls into equivalent ODBC calls.0 API consists of 2 packages: 1. 1997. The JDBC API presents a standard API to access a wide range of underlying data sources or legacy systems. Type 1.
The driver translates JDBC specific calls into vendor specific API calls. This type of drivers are implemented by several application servers. These servers translate the call into a native driver call which handles the actual DB connection. Pure Java Drivers These are the most efficient drivers. which in turn. Type 4. The client application sends a JDBC call through a JDBC driver to the intermediate Database servers.JDBC Type 2. It is much faster than the Type 1 drivers. 90 . The JDBC API calls are converted to direct network calls using vendor provided protocols.10 . Part Native Driver The drivers in this category use a combination of Java implementation and vendor specific APIs for DB access. The DB returns the result of the call to the API. like WebLogic (of BEA Systems) or Inprise Application Server (of Borland). forwards them to the JDBC driver. All major vendors provide type 4 JDBC drivers for their Database products. Part Java. Type 3. Intermediate Database Access Server Type 3 drivers are DataBase servers which act as intermediate tier between multiple clients and multiple Database servers. because it eliminates one level of indirection.
3 the java.Array java.sql.0).CallableStatement java.Date java. java.sql.DriverManager java.org/en/jsr/detail?id=221.sql.sql.SQLData java.0 API.Statement java. let's remind some of the most important ones.sql.sql.Clob java.sql.sql.SQLDataException java.ResultSetMetaData java. defined in the JDBC 3.JDBC 10. An exhaustive list of the classes and interfaces of this package can be found in the latest JDBC specification (4.sql.sql.sql.SQLWarning java.Time java.10 .sql.Connection java.Wrapper 91 .SQLInput java.SQLOutput java.ResultSet java.sql.Timestamp java.SQLXML java. The document containing this specification is JSR 221 and can be viewed at http://jcp. Of the 80+ classes and interfaces defined in this specification.sql.Blob java.Struct java.sql.sql.sql.sql.sql package This package contains the core JDBC API.sql.Types java.sql.PreparedStatement java.SQLPermission java.SQLException java.sql.Driver java.sql.sql.sql.sql.
sql.sql.Clob java.sql.sql.sql.RowId java.sql. querying the database 4.DatabaseMetaData java.PreparedStatement java.SQLFeatureNotSupportedException java.sql.sql.sql.SQLTimeoutException java.StatementEventListener 10.StatementEvent javax.sql.Blob java.CommonDataSource javax. establishing a database connection 3.SQLDataException java. java.SQLTransientConnectionException java.RowIdLifeTime java.SQLIntegrityConstraintViolationException java.sql.sql.4 interaction schema in the java.sql.sql.sql.SQLSyntaxErrorException java.sql.SQLNonTransientConnectionException java.SQLInvalidAuthorizationSpecException java.NClob java.sql.Statement java.sql.sql.ResultSet java.SQLXML java.sql.sql.SQLTransactionRollbackException java.sql.sql.Connection java.Wrapper javax.JDBC The following list contains all of the classes and interfaces new or updated in version 4. processing the result set 92 .SQLTransientException java.CallableStatement java.Types java.sql.0.10 .sql.SQLWarning java.sql.sql package The figure below shows the interactions and relationships between the major classes and interfaces of the java.sql.ClientinfoStatus java.SQLClientInfoException java.sql.SQLOutput java.sql.SQLInput java. loading a database driver 2.sql.sql.SQLException java.sql. The main steps in communicating with a database are: 1.sql.SQLNonTransientException java.sql package.sql.
JDBC 10.datastore.OracleDriver sun.odbc. The first one is loading a database driver.sybase.DB2Driver oracle.DataStoreDriver com.net.10 . Here are some examples of actual database driver names: • • • • • com.jdbc.jdbc.ibm.driver.borland.db2.jdbc. A database driver is specified by the driver name.SybDriver com.jdbc.JdbcOdbcDriver 93 .jdbc.5 loading a DB driver connecting to the database There are two main steps in connecting to an existing database.
String user = "root".mm. let's have a better look in the next section at the DriverManager class.gjt. import java.bank11. 94 .util. passwd). user. the sub-protocol is used to identify the JDBC driver.Driver"). Since we just used it. the only protocol allowed in JDBC). The URL has 3 parts separated by colons.*.sql. Here is some sample code which shows how this is done: String connURL = "jdbc:mysql://localhost:3306/ccards".JDBC The Java code to load the driver name is somewhat obscure. as specified by the driver vendor. subname – the syntax of this field is vendor specific and allows the identification Here are some examples of JDBC driver URLs: jdbc:sybase:localhost:2025 jdbc:db2://db2. } The actual location of the database is specified by its URL (also known as connection URL).newInstance().mysql. as follows: jdbc:<subprotocol>:subname • • • jdbc is the protocol name (actually. try { Class.*.printStackTrace(). but let's take it for granted: import java. } catch (Exception e) { // driver not found e.10 . String passwd = "root" Connection conn = DriverManager.getConnection(connURL.com:50002/ccards jdbc:oracle:thin:@loclahost:1521:ORCL • • • The second step in connecting to an existing database is to open the connection. by using the connection URL.forName("org.
6 the DriverManager class This class belongs to the javax.sql package and offers a common access layer on top of different JDBC drivers.7 the Connection interface The Connection interface is part of then javax. int resultSetConcurrency. int resultSetHoldability) PreparedStatement prepareStatement(String sql) throws SQLException CallableStatement prepareCall(String sql) throws SQLException 95 . "true").getConnection(connURL.Properties info) throws SQLException While the first two forms of getConnection() are pretty straightforward. prp).put("create". let's see an example of how to use the last of the three forms. Here they are: public static Connection getConnection(String connURL) throws SQLException public static Connection getConnection(String connURL. "true").JDBC 10. There are 3 versions of the getConnection() method of the DriverManager class. Properties prp = new Properties(). int resultSetConcurrency) throws SQLException Statement createStatement(int resultSetType.10 . Connection conn = DriverManager.util. The most important methods for creating statements: Statement createStatement() throws SQLException Statement createStatement(int resultSetType. 10. Once we get the hold of a Connection object. but we will restrict ourselves to creating SQL statements.put("autocommit". String passwd) throws SQLException public static Connection getConnection(String connURL.sql package. prp. we can use it for various purposes. java. Each driver used by the application must be registered (loaded) before the DriverManager class tries to obtain a connection. String user. prp.
other methods: • • • • • • setQueryTimeout() getQueryTimeout() setMaxFieldSize() getMaxFieldSize() cancel() getConnection() 96 .8 statement interfaces The objects we encountered in the previous section. respectively. methods for batch updates: • • • addBatch() executeBatch() clearBatch() 3. prepared statements and stored procedures. Statement. The Statement interface has (among others) the following methods: 1. method to get the current result set: • getResultSet() 5. methods for result set concurrency and type: • • getResultSetConcurrency() getResultSetType() 6. methods for executing statements: • • • execute() executeQuery() executeUpdate() 2. methods for result set fetch size and direction: • • • • setFetchSize() getFetchSize() setFetchDirection() getFetchDirection() 4. PreparedStatement and CallableStatement abstract regular SQL statements.JDBC 10.10 . namely.
stmt.sql.JDBC The Statement interfaces also support the same methods for transaction support as the Connection objects. 10.. Methods to retrieve data: • • • • • • • • • • • • • • • • • • • • getAsciiStream() getBoolean() getDate() getInt() getShort() getTimeStamp() getBinaryStream() getBytes() getFloat() getObject() getTime() getString() getByte() getDouble() getLong() getBigDecimal() getMetaData() getClob() getWarnings() getBlob() 97 . The interface ResultSet is implemented by driver vendors.10 .".9 the ResultSet interface The result of a query by a Statement object is a java. Here is a typical example: Statement stmt = conn..ResultSet object which is available to the user and allows access to the data retrieved. String sqlString = "CREATE TABLE customer .executeUpdate(sqlString). Objects implementing the Connection interface are mainly used for SQL queries execution.createStatement().
a concurrency of read only. and cursors are held over commit boundaries. An exception to this is that WebSphere currently changes the cursor holdability default so that cursors are implicitly closed when committed. not at 0) or the column name. What if we don't have this knowledge? Fortunately. all created ResultSets have a type of forward only.10 . all this data about the DB schema (or metadata) can be retrieved using the ResultSetMetaData interface. The usage of these retrieval methods assumes the prior knowledge of the type and the index (or name) of a particular column. Here are the most important methods specified by the ResultSetMetaData interface: • • • • • • • • • • • • • • • • • • • • getCatalogName() getTableName() getSchemaName() getColumnCount() getColumnName() getColumnLabel() getColumnType() getColumnTypeName() getColumnClassName() getColumnDisplaySize() getScale() getPrecision() isNullable() isCurrency() isSearchable() isCaseSensitive() isSigned() isAutoIncrement() isReadOnly() isDefinitelyWritable() 10. These characteristics are configurable through methods that are accessible on Statement. One can think of a database cursor as an iterator over the collection of rows in the result set.JDBC Most of these methods require the column index (which in SQL starts at 1.10 ResultSet characteristics By default. and CallableStatement objects. as the argument. A cursor comprises a control structure for the successive traversal (and potential processing) of records in a result set. PreparedStatement. The invocation of the getMetaData() method of a ResultSet object returns an object of ResultSetMetaData type. 98 .
10 - JDBC 10.10.1 ResultSet types
The ResultSet type specifies the following about the ResultSet:
• •
Whether the ResultSet is scrollable. The types of Java (TM) Database Connectivity (JDBC) ResultSets that are defined by constants on the ResultSet interface.
Definitions of these ResultSet types are as follows:
A cursor that can only be used to process from the beginning of a ResultSet to the end of it. This is the default type.
A cursor that can be used to scroll in various ways through a ResultSet. This type of cursor is insensitive to changes made to the database while it is open. It contains rows that satisfy the query when the query was processed or when data is fetched.
A cursor that can be used to scroll in various ways through a ResultSet. This type of cursor is sensitive to changes made to the database while it is open. Changes to the database have a direct impact on the ResultSet data. JDBC 1.0 ResultSets are always forward only. Scrollable cursors were added in JDBC 2.0. Note: The blocking enabled and block size connection properties affect the degree of sensitivity of a TYPE_SCROLL_SENSITIVE cursor. Blocking enhances performance by caching data in the JDBC driver layer itself.
10.10.2 Concurrency
Concurrency determines whether the ResultSet can be updated. The types are again defined by constants in the ResultSet interface. The available concurrency settings are as follows:
A ResultSet that can only be used for reading data out of the database. This is the default setting.
A ResultSet that allows you to make changes to it. These changes can be placed into the underlying database. JDBC 1.0 ResultSets are always forward only. Updateable ResultSets were added in JDBC 2.0. Note: According to the JDBC specification, the JDBC driver is allowed to change the ResultSet type of the ResultSet concurrency setting if the values cannot be used together. In such cases, the JDBC driver places a warning on the Connection object. There is one situation where the application specifies a TYPE_SCROLL_INSENSITIVE, CONCUR_UPDATEABLE ResultSet. Insensitivity is implemented in the database engine by making a copy of the data. You are then not allowed to make updates through that copy to the underlying database. If you specify this combination, the driver changes the sensitivity to TYPE_SCROLL_SENSITIVE and create the warning indicating that your request has been changed.
10.10.3 Holdability
The holdability characteristic determines whether calling commit on the Connection object closes the ResultSet. The JDBC API for working with the holdability characteristic is new in version 3.0. However, the native JDBC driver has provided a connection property for several
releases that allows you to specify that default for all ResultSets created under the connection. The API support overrides any setting for the connection property. Values for the holdability characteristic are defined by ResultSet constants and are as follows:
All open cursors remain open when the commit clause is called. This is the native JDBC default value.
All open cursors are closed when commit clause is called.
10.11 example of data retrieval
// DisplayServlet.java package com.bank11.ccards.servlets; import import import import import java.sql.*; javax.servlet.*; javax.servlet.http.*; java.math.*; java.util.*;
public class DisplayServlet extends HttpServlet { Connection conn; // Initializes the servlet public void init(ServletConfig config) throws ServletException { super.init(config); String driverName = "org.gjt.mm.mysql.Driver"; try { Class.forName("org.gjt.mm.mysql.Driver"); } catch(ClassNotFoundException e) { e.printStackTrace(); } String connURL="jdbc:mysql://localhost:3306/ccards"; try { conn=DriverManager.getConnection(connURL,"root","root"); } catch (SQLException sqle) { sqle.printStackTrace(); } } // Destroys the servlet.
public void destroy() { } // Processes requests for both HTTP GET and POST methods. protected void processRequest(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException { String theCode = req.getParameter("CODE"); String sql = "SELECT FIRST_NAME, LAST_NAME, ACCOUNT_NUM from CUSTOMERS where CNP="+theCode+";"; try { Statement stmt = conn.getStatement(); ResultSet rs = stmt.executeQuery(sql); while(rs.next()) { String firstName = rs.getString("FIRST_NAME"); String lastName = rs.getString("LAST_NAME"); BigDecimal accountNum = rs.getBigDecimal("ACCOUNT_NUM"); } } catch (SQLException sqle) { sqle.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } resp.setContentType("text/html"); java.io.PrintWriter out = resp.getWriter(); // output your page here out.println("<html>"); out.println("<head>"); out.println("<title>Servlet</title>"); out.println("</head>"); out.println("<body>"); ... out.println("</body>"); out.println("</html>"); out.close(); } // Handles the HTTP GET method. protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException { processRequest(req, resp); } // Handles the HTTP POST method. protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException {
processRequest(req, resp); } // Returns a short description of the servlet. public String getServletInfo() { return "Short description"; } }
10.12 the PreparedStatement interface
If an SQL statement is used several times and its different forms differ only with respect to the data they specify, a better choice is the usage of a PreparedStatement object. Prepared statements are parametrized and each parameter (usually, a field (column) value or name) is represented by a question mark '?'. The following lines of Java code give an example of how to use PreparedStatement objects: Statement stmt = con.createStatement(); PreparedStatement pstmt = con.prepareStatement("INSERT INTO customer VALUES (?, ?, ?)"); stmt.executeUpdate("CREATE TABLE customer varchar(32) lastName varchar(24))"); // set parameters for preparedStatement pstmt.setInt(1, 1021); pstmt.setString(2, "Vasile"); pstmt.setString(3, "Dumitrascu"); int count = pstmt.executeUpdate(); (id int, firstName
10.13 jdbc and sql types and their corresponding java classes
JDBC Type ARRAY BIGINT BINARY BIT BLOB CHAR CLOB DATE Purpose SQL array 64 bit integer binary value one bit value binary large object char string character large object day, month, year SQL Type ARRAY BIGINT none BIT BLOB CHAR CLOB DATE Java Type java.sql.Array long byte[] boolean java.sql.Blob String java.sql.Clob java.sql.Date
Time java. the DriverManager interface is replaced by the DataSource interface as main method of obtaining DB connections. This interface is.produces a Connection object that will 103 .sql package. It is part of the javax.Times tamp short byte[] String 16 bit integer SMALLINT short Purpose decimal value distinct double precision double precision 32 bit integer stores Java objects variable length binary value variable length char string null values decimal value db specific types single precision SQL Type DECIMAL DISTINCT DOUBLE PRECISION FLOAT INTEGER none none none NULL NUMERIC none REAL Java Type java. basicly.sql. the new mechanism uses a centralized JNDI service to locate a javax.Big Decimal Object float 10. The DataSource interface is implemented by a driver vendors.DataSource object.math. time. There are three types of implementations: 1.Big Decimal none double double int Object byte[] String null java.14 JDBC Data Sources In the JDBC 2.sql.10 .math. Connection pooling implementation -. nanoseconds 8 bit integer variable length binary value variable length char string TIME TIMESTAMP TINYINT none VARCHAR java.produces a standard Connection object 2. Basic implementation -. mins. While the DriverManager interface was used at run time to load explicitly a JDBC driver.sql.JDBC JDBC Type DECIMAL DISTINCT DOUBLE FLOAT INTEGER JAVA_OBJECT LONGVARBINARY LONGVARCHAR NULL NUMERIC OTHER REAL REF SMALLINT STRUCT TIME TIMESTAMP TINYINT VARBINARY VARCHAR hrs. secs date. a factory for creating DB connections.0 optional package.
*. } public void init() throws ServletException { if (theDataSource == null) { try { Context env = (Context) new InitialContext().10 . import import import import import import java. public void setDataSource(DataSource dataSource) { theDataSource = dataSource. 3. javax. } public DataSource getDataSource() { return theDataSource.*. This implementation works with a middle-tier transaction manager and almost always with a connection pooling manager. This implementation works with a middletier connection pooling manager. throws public class TestDataSource extends HttpServlet { private final static Logger log = Logger. javax.lookup(DATASOURCE_NAME).sql.servlets. 104 . theDataSource = (DataSource) env.*.ccards.http.class.servlet.getName()). Main methods: public Connection getConnection() throws SQLException public Connection getConnection(String user. private final static String DATASOURCE_NAME = "jdbc/ccards".JDBC automatically participate in connection pooling.*. javax.*. private DataSource theDataSource.*.servlet.sql. String pwd) SQLException A servlet example using the DataSource interface: package com. javax.getLogger(TestDataSource.io. java.bank11.lookup("java:comp/env").naming. Distributed transaction implementation -.produces a Connection object that may be used for distributed transactions and almost always participates in connection pooling.
} catch (NamingException e) { throw new ServletException(e).10 .. } } 105 . ServletException { .JDBC if (theDataSource == null) throw new ServletException("`" + DATASOURCE_NAME + "' is an unknown DataSource").. } } } public void doGet(HttpServletRequest request. HttpServletResponse response) throws IOException.
jsp.jsp defines two interfaces – JspPage and HttpJspPage.jsp. 11. The current JSP specification is JSP 2. 11.jsp package contains a number of classes and interfaces that describe and define the contracts between a JSP page implementation class and the runtime environment provided for an instance of such a class by a conforming JSP container. The JSP specific interfaces. namely javax. A JSP is loaded by a JSP container and is converted (to servlet code).servlet.tagext contains classes and interfaces for the definition of JavaServer Pages Tag Libraries.11 . The package javax.5 Java Servlet specification.jsp. The javax.JSP 11.HttpJspPage interface has a single method: public void jspService(HttpServletRequest req.servlet.jsp and javax.1 and is related to the 2.2 the java. classes and exceptions are part of two packages.3 the generated servlet – an example 106 . HttpServletResponse resp) throws ServletException. The package javax.JspPage interface This interface has 2 methods: public void jspInit() public void jspDestroy() The javax.servlet.tagext. The JspPage interface is the interface that a JSP processor-generated class must satisfy. the servlet code is regenerated. The interface HttpJspPage is the interface that a JSP processor-generated class for the HTTP protocol must satisfy.servlet. JSR 245 is the official document containing the current specification of JSP. IOException The implementation of this method is generated by the web container – never by the developer.servlet.1 java server pages as part of web applications A Java Server Page (JSP) is a standard HTML or XML file which contains new scripting tags.servlet. If the JSP is modified.servlet.JSP 11 .
Even if we start with a very benign java server page, like the listed "hello world" example below, the generated servlet is still pretty complex. First, the original index.jsp file. <%-Document : index Created on : 08.11.2010, 08:17:39 Author : sm --%> <%@page contentType="text/html" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>JSP Page</title> </head> <body> <h1>Hello World!</h1> </body> </html> The generated servlet follows. package org.apache.jsp; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent { private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory(); private static java.util.Vector _jspx_dependants; private org.glassfish.jsp.api.ResourceInjector _jspx_resourceInjector; public Object getDependants() {
return _jspx_dependants; } public void _jspService(HttpServletRequest request, HttpServletResponse response) throws java.io.IOException, ServletException { PageContext pageContext = null; HttpSession session = null; ServletContext application = null; ServletConfig config = null; JspWriter out = null; Object page = this; JspWriter _jspx_out = null; PageContext _jspx_page_context = null; try { response.setContentType("text/html;charset=UTF-8"); response.setHeader("X-Powered-By", "JSP/2.1"); pageContext = _jspxFactory.getPageContext(this, request, response, null, true, 8192, true); _jspx_page_context = pageContext; application = pageContext.getServletContext(); config = pageContext.getServletConfig(); session = pageContext.getSession(); out = pageContext.getOut(); _jspx_out = out; _jspx_resourceInjector = (org.glassfish.jsp.api.ResourceInjector) application.getAttribute("com.sun.appserv.jsp.resource.injector"); out.write("\n"); out.write("\n"); out.write("\n"); out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\"\n"); out.write(" \"http://www.w3.org/TR/html4/loose.dtd\">\n"); out.write("\n"); out.write("<html>\n"); out.write(" <head>\n"); out.write(" <meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\n"); out.write(" <title>JSP Page</title>\n"); out.write(" </head>\n"); out.write(" <body>\n"); out.write(" <h1>Hello World!</h1>\n"); out.write(" </body>\n"); out.write("</html>\n");
} catch (Throwable t) { if (!(t instanceof SkipPageException)){ out = _jspx_out; if (out != null && out.getBufferSize() != 0) out.clearBuffer(); if (_jspx_page_context != null) _jspx_page_context.handlePageException(t); else throw new ServletException(t); } } finally { _jspxFactory.releasePageContext(_jspx_page_context); } } } A short comment. The class HttpJspBase is a vendor-implemented class, whose declaration clarifies its relationship with the standard JSP classes and interfaces. public abstract class HttpJspBase extends javax.servlet.http.HttpServlet implements javax.servlet.jsp.HttpJspPage
11.4 ordinary java beans
A java bean is a java class which: implements the java.io.Serializable interface provides a no-argument constructor for each of its properties, provides get and set methods implements a property change mechanism
• • • •
Here is a typical example of a java bean. /* * NewBean.java */ import java.beans.*; import java.io.Serializable; /** * @author sm */ public class NewBean extends Object implements Serializable {
public static final String PROP_SAMPLE_PROPERTY = "sampleProperty"; private String sampleProperty; private PropertyChangeSupport propertySupport; public NewBean() { propertySupport = new PropertyChangeSupport(this); } public String getSampleProperty() { return sampleProperty; } public void setSampleProperty(String value) { String oldValue = sampleProperty; sampleProperty = value; propertySupport.firePropertyChange(PROP_SAMPLE_PROPERTY, oldValue, sampleProperty); } public void addPropertyChangeListener(PropertyChangeListener listener) { propertySupport.addPropertyChangeListener(listener); } public void removePropertyChangeListener(PropertyChangeListener listener) { propertySupport.removePropertyChangeListener(listener); } }
11.5 jsp tags
There are 3 categories of JSP tags (elements): 1. directives – affect the structure of the whole jsp 2. scripting elements – java code inserted in the JSP page 3. actions – special tags affecting the run time behaviour of the JSP Rules for JSP tags:
• •
attribute values are always quoted (single or double quotes) URLs follow the servlet conventions
It has the following format: <%@taglib uri="tagLibUri" prefix="tagPrefix" %> where the tagPrefix indicates a name scope. %> attributes: • • • • • • • • • • • language – values: "java" extends – superclass of the generated class import – list of packages classes session – "true" or "false".JSP • if the URL does not start with / . it is interpreted relative to the position of the current JSP 11. The format of this directive: <%@include file="fileName" %> The taglib directive allows the usage of custom tags (tag extensions).. The general format of a JSP directive is as follows: <%@directive_name attr1="val1" . attrn="valn" %> Ther are three JSP directives: page. in case of error The include directive instructs the container to include inline the content of the resource specified by "fileName". the implicit session object is available buffer – buffering model for the output stream autoflush – if "true". the buffer is flushed automatically if full isThreadSafe – "true" or "false" isErrorPage – "true" or "false" contentType – MIME type of the response info errorPage – the URL of an error page.. include and taglib.. The page directive format: <%@page attr1="val1" ..11 .6 jsp directives The JSP directives are messages sent by the Java Server Page to the JSP container. 111 . These directives do not produce any client output and affect the whole JSP file.
11. Assigns it to available name or id.7.7. 11.3 expressions <%= java expressions to be evaluated %> A scriptlet that sends a value of a Java expression to back to the client. The syntax for this action is: <jsp:useBean id="beanName" scope="sName" beandetails /> 112 . It is evaluated at request processing time and the result is converted to a string which is then displayed.2 scriptlets <% valid java statements %> Block of java code which is executed during request processing. 11. The standard actions are detailed in the next paragraphs.1 declarations <%! java vars and method declarations %> Basicly. a bloc of java code used to define class-wide variables and methods in the generated servlet.4 standard actions Tags that affect the runtime behaviour of the JSP and the response to the client. 11.8 the useBean standard action <jsp:useBean> Used to instantiate a Java bean or locate a bean instance.7.JSP 11. A tag can be embedded into a JSP page.11 . this code goes to inside the service() method. In Tomcat.7 scripting elements 11.7.
The syntax for this action is: <jsp:setProperty name="beanName" propertydetails /> where propertydetails is one of the following: • • • • property="*" property="propertyName" property="propertyName" param="parameterName" property="propertyName" value="propertyValue" where propertyValue is a string or a scriptlet. property="propertyName" value="{ string | <%= expression %> }" .11 .10 the getProperty standard action <jsp:getProperty> 113 .JSP where beandetails is one of the following: • • • • class="className" class="className" type="typeName" beanName="beanName" type="typeName" type="typeName" 11. The property names in the Bean must match the request parameters property="propertyName" [ param="parameterName" ] .the name of a bean instance. you must specify param. The request parameter can have a different name than the Bean property. The value can be a String or an Expression • • 11.Sets one Bean property to a specific value. and if so.stores all of the values in the request object parameters (called request parameters) in matching Bean properties. Attributes description: • • • name .Sets one Bean property to the value of one request parameter.9 the setProperty standard action <jsp:setProperty> Used in conjunction with the <jsp:useBean> action to set the value of the bean properties. already defined in a <jsp:useBean> property – specifies the relationship between request parameters and corresponding bean properties property="*" .
12 the include standard action <jsp:include> Used for the inclusion of a static or dynamic resource into the current JSP page at request processing time. An included page has access only to the JspWriter object and cannot set headers or cookies. The syntax for this action is: <jsp:getProperty name="beanName" property="propName" /> Attributes description: • • name . 11.JSP Used to access the properties of a bean. converts them to string and displays the output to the client. The syntax for this action is: <jsp:include page="pageURL" flush="true" /> Attributes description: • • page .name of the property to be retrieved 11. It is used in conjunction with the <jsp:include>. same format as the <%@include> directive. the <jsp:include> action is executed at request processing time and has static or dynamic content. While the <%@include> directive is executed at compile time and has static content.the name of a bean instance whose property is to be retrieved property . <jsp:forward>.11 .13 the forward standard action 114 .only the "true" value is supported.11 the param standard action <jsp:param> Provide other tags with additional information in the form of name:value pairs. flush . <jsp:plugin> actions. The syntax for this action is: <jsp:param name="paramName" value="paramValue" /> 11.the URL of the page.
when we want to separate the application into different views. You must include the . followed by the execution of the applet or JavaBeans component specified by the tag. codebase="classFileDirectoryName" .. You must specify either bean or applet." . as well. which makes it possible for applets or Beans called by the same JSP file to communicate with each other.the name of the Java class file that the plugin will execute. archive="URIToArchive.class extension in the name following code.the name of a bean instance.. depending on request.a name for the Bean or applet instance. 11. code="classFileName" . the path of the JSP file that calls <jsp:plugin> is used. The filename is relative to the directory named in the codebase attribute.11 .JSP <jsp:forward> Used to forward the the request to another JSP. If you do not supply a value. The syntax for this action is: <jsp:plugin type="bean|applet" code="objCode" codeBase="objCodeBase" align="align" archive="archiveList" height="height" hspace="hSpace" jreversion="jreVersion" name="componentName" vspace="vSpace" width="width" nspluginurl="netscapeURL" iepluginurl="IEURL"> <jsp:params> <jsp:param name="paramName" value="paramValue" /> </jsp:params> </jsp:plugin> Attributes description: • • • .. ... The syntax for this action is: <jsp:forward page="pageURL" /> The action may include several <jsp:param> tags. servlet or to a static resource.the type of object the plugin will execute. already defined in a <jsp:useBean> type="bean|applet" .a comma-separated list of paths that locate archive files • • • 115 .the absolute or relative path to the directory that contains the applet's code. It is used mainly. name .14 the plugin standard action <jsp:plugin> Used in pages to generate client browser specific HTML tags (<OBJECT> or <EMBED>) that result in download of Java plugins(if required). as this attribute has no default value. name="instanceName" .
Object type and scope page 11. out . • align="bottom|top|middle|left|right" . Must be a small nonzero number. of the image the applet or Bean displays.represents the object that triggered the service() method invokation and has type HttpServletRequest with scope request 2.PrintWriter. request . nspluginurl="URLToPlugin" . it has java. in pixels. the object can be accessed by invoking the getAttribute() method on the implicit 116 . it has HttpServletResponse type and page scope 3. session .servlet. it has type ServletContext and scope application 6.it is an instance of the page's implementation of the servlet class.it has HttpSession type and session scope 5. iepluginurl="URLToPlugin" • • • • • 11.15 implicit objects JSP provides several implicit objects. it has javax.11 .io. writes to the output stream to the client. request .the version of the Java Runtime Environment (JRE) the applet or Bean requires. config .it is the SevletConfig for the current JSP page.jsp. jreversion="JREVersionNumber|1. it is of type ServletConfig and has page scope 8. The default value is 1.lang. application . 1.represents the servlet context.the initial height and width.the amount of space.an object with request scope is bound to the HttpServletRequest object.JspWriter type and scope page 7. with a protocol name.provides a single point of access to attributes and shared data within the page. page .JSP to be preloaded with a class loader located in the directory named in codebase. in pixels.the URL where the user can download the JRE plugin for Netscape Navigator. hspace="leftRightPixels" vspace="topBottomPixels" . to the left and right (or top and bottom) of the image the applet or Bean displays. pageContext . not counting any windows or dialog boxes the applet or Bean brings up. optional port number. The value is a full URL. objects which are automaticly available.it represents the buffered version of java. based on the servlet API.1. height="displayPixels" width="displayPixels" . and domain name.represents server's response to the request. response .the positioning of the image displayed by the applet or Bean relative to the line in the JSP result page that corresponds to the line in the JSP file containing the <jsp:plugin> tag.1" . it has type PageContext with scope page 4.16 scopes 1.
<%@page contentType="text/html" errorPage="error. Object value) method 3.invalidAcct()) { %> <jsp:forward page="retry. Object value) method 4.an object with application scope is bound to the ServletContext object.userExists()) { %> <jsp:forward page="retry.registeredAcct()) { %> <jsp:forward page="response. session . the object can be accessed by invoking the getAttribute() method on the implicit pageContext object.17 a short example The following is the Enroll.an object with session scope is bound to the HttpSession object.jsp"%> <jsp:useBean id="enrollBean" scope="session" class="com.bank11. page .jsp"> <jsp:param name="resolution" value="userExists"/> </jsp:forward> 117 .an object with page scope is bound to the PageContext object.beans. the generated servlet binds the object to HttpServletRequest object using the setAttribute(String key. application . the object can be accessed by invoking the getValue() method on the implicit session object. the generated servlet binds the object to PageContext object using the setAttribute(String key.jsp"> <jsp:param name="resolution" value="registeredAcct"/> </jsp:forward> <% } else if (enrollBean. the generated servlet binds the object to the ServletContext object using the setAttribute(String key.jsp file. if (enrollBean. the generated servlet binds the object to HttpSession object using the setAttribute(String key. Object value) method 2.EnrollBean" /> <jsp:setProperty name="enrollBean" property="*" /> <% enrollBean.11 .ccards.jsp"> <jsp:param name="resolution" value="invalidAcct"/> </jsp:forward> <% } else if (enrollBean.JSP request object. Object value) method 11.init(). the object can be accessed by invoking the getAttribute() method on the implicit application object.
examples. private SimpleSubBean subBean. } // Sets the string property public void setString(String value) { 118 . private boolean flag.18 an extended example This example is provided by Devsphere.java: package com. private int integer. SimpleBean.JSP <% } else { enrollBean. %> <jsp:forward page="response. The public constructor could have been omitted.18.mapping. an int. // No-arg constructor public SimpleBean() { } // Gets the string property public String getString() { return this. a boolean and another String).1 Data beans SimpleBean is a Java bean that contains several standard properties (a String. private int list[].devsphere. private float number.jsp"> <jsp:param name="resolution" value="userEnrolled"/> </jsp:forward> <% } %> 11.11 . // Simple bean public class SimpleBean implements java.register(). 11. private String optional. two indexed standard properties (a String[] and an int[]) and another data bean (a SimpleSubBean).simple.io. The SimpleBean class is declared public. a software development and consulting company. a float.Serializable { private String string. has a no-arg constructor and provides accessors (get & set methods) for its properties. private String colors[]. since the Java compiler generates one in the absence of any other constructors.string.
} // Gets an element of the colors property public String getColors(int index) { return this.colors = values. } // Gets the colors property public String[] getColors() { return this.number. } // Sets the number property public void setNumber(float value) { this.JSP this.colors[index].integer. } // Gets the integer property public int getInteger() { return this. } 119 .colors. } // Sets the colors property public void setColors(String values[]) { this.flag.number = value. } // Sets the integer property public void setInteger(int value) { this. } // Gets the number property public float getNumber() { return this.11 .integer = value.flag = value. } // Sets the flag property public void setFlag(boolean value) { this. } // Gets the flag property public boolean getFlag() { return this.string = value.
} // Gets the optional property public String getOptional() { return this.colors[index] = value. String value) { this. } // Sets the list property public void setList(int values[]) { this. } // Gets the list property public int[] getList() { return this. } // Gets an element of the list property public int getList(int index) { return this. } // Sets an element of the list property public void setList(int index. } // Sets the subBean property public void setSubBean(SimpleSubBean value) { this. } // Gets the subBean property public SimpleSubBean getSubBean() { return this. } // Sets the optional property public void setOptional(String value) { this. int value) { this.list = values. } } 120 .optional = value.11 .subBean.list[index].list[index] = value.optional.JSP // Sets an element of the colors property public void setColors(int index.list.subBean = value.
SimpleSubBean.Serializable { private String string.string = value.18.io.JSP SimpleSubBean contains only two standard properties (a String and a float).11 .html: Name string number integer flag Property type String float int boolean Element type text text radio[] checkbox 121 . } // Sets the number property public void setNumber(float value) { this.mapping.2 the HTML Form The properties of SimpleBean are mapped to the form elements of SimpleForm.java: package com.examples. } // Gets the number property public float getNumber() { return this.string. } } 11.number = value.number.devsphere. // Simple sub-bean public class SimpleSubBean implements java. private float number. // No-arg constructor public SimpleSubBean() { } // Gets the string property public String getString() { return this.simple. } // Sets the string property public void setString(String value) { this.
JSP colors list optional subBean.11 .html: <HTML> <HEAD><TITLE>Simple form</TITLE></HEAD> <BODY> <H3>Simple Example</H3> <FORM METHOD="POST"> <P> String <BR> <INPUT TYPE="TEXT" NAME="string" SIZE="20"> <P> Number <BR> <INPUT TYPE="TEXT" NAME="number" SIZE="20"> <P> Integer <BR> <INPUT TYPE="RADIO" NAME="integer" VALUE="1">Option 1 <INPUT TYPE="RADIO" NAME="integer" VALUE="2">Option 2 <INPUT TYPE="RADIO" NAME="integer" VALUE="3">Option 3 <P> Flag <BR> <INPUT TYPE="CHECKBOX" NAME="flag">Flag <P> Colors <BR> <INPUT TYPE="CHECKBOX" NAME="colors" VALUE="red">Red <INPUT TYPE="CHECKBOX" NAME="colors" VALUE="green">Green <INPUT TYPE="CHECKBOX" NAME="colors" VALUE="blue">Blue <P> List <BR> <SELECT NAME="list" SIZE="3" MULTIPLE> <OPTION VALUE="1">Item 1</OPTION> <OPTION VALUE="2">Item 2</OPTION> <OPTION VALUE="3">Item 3</OPTION> </SELECT> <P> Optional <BR> <INPUT TYPE="TEXT" NAME="optional" SIZE="20"> String[] int[] String String float checkbox[] select text text text 122 .string subBean.number SimpleForm.
string" SIZE="20"> <P> Number (subBean) <BR> <INPUT TYPE="TEXT" NAME="subBean.18. a float. The default values for the properties of the contained bean could have been defined in another resource bundle called SimpleSubBeanResources. the form's name and the processor's name.java: package com.number" SIZE="20"> <P> <INPUT TYPE="SUBMIT" VALUE="Submit"> <INPUT TYPE="RESET" VALUE="Reset"> </FORM> </BODY> </HTML> 11.123) }. "One or more colors must be selected" }. The mapping framework contains default error messages for each type of form element. { "[OPTIONAL_PROPERTIES]".ListResourceBundle { private static final Object[][] contents = { { "[DEFAULT_VALUE.11 . "One or more items must be selected" }. "An option must be selected" }. { "[ERROR_MESSAGE. The list of optional properties has a single element. SimpleBeanResources. No error is signaled if the user doesn't provide a value for this property. { "[DEFAULT_VALUE. The processing order isn't necessary to this example.examples. These two resources aren't accessed by the mapping utilities.devsphere. a boolean and an int[].mapping.list]".util.integer]".flag]".JSP <P> String (subBean) <BR> <INPUT TYPE="TEXT" NAME="subBean. the processing order. "abc" }.simple. It has been included here just for demonstrative purposes. The primitive values must be wrapped by a Float and a Boolean in order to be stored as resources.colors]". new Boolean(true) }.3 bean resources The SimpleBeanResources class is a resource bundle containing optional information that is useful to the mapping process: default values. new int[] { 2. The default values are defined for a String. the list of optional properties. public class SimpleBeanResources extends java. error messages.number]".list]". { "[DEFAULT_VALUE. Their role is to help the users to correct the input errors. { "[DEFAULT_VALUE. new Float(0.string]". 3 } }. new String[] { 123 . There are three error messages. { "[ERROR_MESSAGE. { "[ERROR_MESSAGE. The form's name and the processor's name are used by the JSP handler described in the next section.
com.JSP "optional" } }.devsphere. "integer". "number". } } 11. { "[PROC_NAME]".*" %> <jsp:useBean id="simpleBean" scope="request" class="com. "optional".devsphere.devsphere.SimpleBean"/> <% // Get the bean resources java.mapping.mapping.jsp handler is based on a template that was described in a previous chapter.mapping.FormUtils inserts the bean data and the error messages into the HTML form. a later section of this chapter lists two JSPs that perform the mapping and build the HTML form without using the framework.devsphere. "subBean" } }.jsp: <%@ page language="java" %> <%@ page import="com. If necessary. { "[PROCESSING_ORDER]".util. a CHECKED attribute for checkboxes and radio buttons that must be selected and a SELECTED attribute for the list items that must be highlighted.*.jsp" } }.simple. "SimpleForm.devsphere. "flag".examples.11 . The error messages that occur during the mapping process are stored in a Hashtable. { "[FORM_NAME]". "colors".html" }.FormUtils sets the bean properties to the values of the request parameters (form data). "list".18. A boolean property is set to true if the request parameter is present no matter what its value is (except "false"). For a better understanding of this example. The formToBean() method of com.4 JSP Handler The SimpleHndl.ResourceBundle beanRes 124 .mapping. SimpleHndl. new String[] { "string".logging. The beanToForm() method of com. string values are converted to numbers. public Object[][] getContents() { return contents. It inserts a VALUE attribute for text elements. "SimpleProc.
formToBean(formData.getString("[FORM_NAME]"). // Construct the form's path String formPath = basePath + beanRes.getServletPath().getBeanResources(simpleBean. // Construct the base path String basePath = request.JSP = HandlerUtils. response). // Get a new document FormDocument document = template. if (isPostMethod && errorTable == null) { // Construct the processor's path String procPath = basePath + beanRes. // Determine the HTTP method boolean isPostMethod = request.getString("[PROC_NAME]").getDocument(). errorTable = HandlerUtils. logger). // Process the valid data bean instance application.getTemplate(new java.removeUserErrors(errorTable).11 .equals("POST"). } else { if (!isPostMethod) // Ignore the user errors if the form is requested with GET. // Wrap the form data FormData formData = new ServletFormData(request).Hashtable errorTable = FormUtils.getRequestDispatcher(procPath).getMethod(). formPath = application.getRealPath(formPath).util.lastIndexOf('/'). basePath = slashIndex != -1 ? basePath. simpleBean.getClass()). // Form-to-bean mapping: request parameters are mapped to bean properties java. slashIndex+1) : "".trim().io.trim(). 125 . // Get the form template FormTemplate template = FormUtils.forward(request. int slashIndex = basePath. // Create a logger that wraps the servlet context ServletLogger logger = new ServletLogger(application).File(formPath)).substring(0.
getColors()) %> <P> list = <%= toString(simpleBean. // Bean-to-form mapping: bean properties are mapped to form FormUtils.mapping.SimpleBean"/> <HTML> <HEAD><TITLE>Simple bean</TITLE></HEAD> <BODY> <H3>Simple Example</H3> <P><B> SimpleBean properties: </B> <P> string = <jsp:getProperty name="simpleBean" property="string"/> <P> number = <jsp:getProperty name="simpleBean" property="number"/> <P> integer = <jsp:getProperty name="simpleBean" property="integer"/> <P> flag = <jsp:getProperty name="simpleBean" property="flag"/> <P> colors = <%= toString(simpleBean. i < list.beanToForm(simpleBean.18.length.string = <%= simpleBean.length == 1 && list[0] != null) return list[0]. errorTable.getList()) %> <P> optional = <jsp:getProperty name="simpleBean" property="optional"/> <P> subBean. StringBuffer strbuf = new StringBuffer().examples.jsp processor gets the beans that were validated by the JSP handler and prints the values of their properties.getSubBean().append("{ "). SimpleProc.send(out).11 . for (int i = 0.simple.JSP elements logger).getString() %> <P> subBean. document.getNumber() %> </BODY> </HTML> <%! public static String toString(String list[]) { if (list == null || list.5 JSP Processor The SimpleProc.number = <%= simpleBean.jsp: <%@ page language="java"%> <jsp:useBean id="simpleBean" scope="request" class="com. i++) 126 . if (list.devsphere.length == 0) return "". strbuf. // Send the form document document. } %> 11.getSubBean().
jsp files to other languages requires a lot of work and could make the maintenance very hard.devsphere.length == 0) return "". } strbuf. return strbuf. } %> 11. return strbuf. strbuf.SimpleBean"/> <jsp:useBean id="errorTable" scope="request" class="java.append("}"). In addition. strbuf. A single call to FormUtils. The localization of the Complex*.simple. default values and error messages are kept in localizable resource bundles. } public static String toString(int list[]) { if (list == null || list.append(" "). Using the framework.jsp files. i < list.jsp generates the HTML form dynamically and inserts default values and error messages.util.JSP if (list[i] != null) { strbuf. It uses 120 lines of Java-JSP-HTML mixture to generate a 40 lines HTML form.18. } strbuf.toString(list[0]).mapping. making the testing and the debugging easier.append(" ").6 without using the devsphere framework ComplexForm.jsp: <%@ page language="java" %> <jsp:useBean id="simpleBean" scope="request" class="com.formToBean() call.Hashtable"/> <HTML> <HEAD><TITLE>Without using the framework</TITLE></HEAD> 127 .append(list[i]).toString(). Using the framework you separate the HTML code from the Java/JSP code. The adding/removing of a bean property requires changes in both Complex*.jsp uses 150 lines of Java-JSP mixture to set the properties of a bean object to the values of the request parameters.11 . strbuf. you only have to add/remove a form element to/from a pure HTML file. beanToForm() handles and logs many types of application errors. StringBuffer strbuf = new StringBuffer().append(list[i]).length. A later chapter shows how to build internationalized applications using the framework. In addition.examples. This is the equivalent of a single FormUtils.length == 1) return Integer. ComplexHndl. if (list.append("{ ").append("}"). for (int i = 0. i++) { strbuf.beanToForm() can do the same using a pure HTML file. ComplexForm.toString().
i < integerLabels. "string") %> <INPUT TYPE="TEXT" NAME="string" VALUE="<jsp:getProperty name="simpleBean" property="string"/>"> <P> Number <BR> <%= getErrorMessage(errorTable. 128 . if (colors == null) colors = new String[0].equals(colorValues[i])) { checked = true.length. j++) if (colors[j].getColors(). "number") %> <INPUT TYPE="TEXT" NAME="number" VALUE="<jsp:getProperty name="simpleBean" property="number"/>"> <P> Integer <BR> <%= getErrorMessage(errorTable.getFlag() ? "CHECKED" : "" %>> Flag <P> Colors <BR> <%= getErrorMessage(errorTable.JSP <BODY> <H3>Equivalent of Simple Example</H3> <FORM METHOD=POST> <P> String <BR> <%= getErrorMessage(errorTable. "flag") %> <INPUT TYPE="CHECKBOX" NAME="flag" <%= simpleBean. j < colors.length. "Blue" }. i++) { int value = i+1.11 . i < colorValues. for (int i = 0. "Option 3" }. "blue" }.length. for (int i = 0. "green". i++) { boolean checked = false. "integer") %> <% String integerLabels[] = { "Option 1". "Green". String colorValues[] = { "red". boolean checked = simpleBean. if (colors != null) for (int j = 0. "Option 2".getInteger() == value. "colors") %> <% String colors[] = simpleBean. %> <INPUT TYPE="RADIO" NAME="integer" VALUE="<%= value %>" <%= checked ? "CHECKED" : "" %>> <%= integerLabels[i] %> <% } %> <P> Flag <BR> <%= getErrorMessage(errorTable. String colorLabels[] = { "Red".
"optional") %> <INPUT TYPE="TEXT" NAME="optional" VALUE="<jsp:getProperty name="simpleBean" property="optional"/>"> <% if (simpleBean.SimpleSubBean()). for (int i = 0.examples.string" VALUE="<%= simpleBean.getString() %>"> <INPUT TYPE="CHECKBOX" NAME="colors" VALUE="<%= colorValues[i] <%= checked ? "CHECKED" : "" %>> <%= colorLabels[i] %> 129 . break. i++) { int value = i+1. "Item 3" }.length. "subBean. String listItems[] = { "Item 1".simple. "list") %> <SELECT NAME="list" SIZE="3" MULTIPLE> <% int list[] = simpleBean.setSubBean( new com. boolean selected = false.mapping. "Item 2". j++) if (list[j] == value) { selected = true. if (list != null) for (int j = 0.getSubBean().string") %> <INPUT TYPE="TEXT" NAME="subBean. } %> <OPTION VALUE = "<%= value %>" <%= selected ? "SELECTED" : "" %>> <%= listItems[i] %> <% } %> </SELECT> <P> Optional <BR> <%= getErrorMessage(errorTable.getSubBean() == null) simpleBean.length. } %> %>" <% } %> <P> List <BR> <%= getErrorMessage(errorTable. i < listItems.getList().11 . j < list. %> <P> String (subBean) <BR> <%= getErrorMessage(errorTable.devsphere.JSP break. if (list == null) list = new int[0].
Hashtable"/> <% simpleBean.get(property).examples. boolean isPostMethod = request.setSubBean(simpleSubBean). if (isPostMethod) { //* string : text %> <jsp:setProperty name="simpleBean" property="string"/> <% if (simpleBean.length() == 0) { simpleBean. return message.util.getString(). String property) { String message = (String) errorTable.devsphere.SimpleBean"/> <jsp:useBean id="simpleSubBean" scope="page" class="com.simple.util.getMethod().devsphere.simple.SimpleSubBean"/> <jsp:useBean id="errorTable" scope="request" class="java.examples.getSubBean().equals("POST").getString() == null || simpleBean.11 .number") %> <INPUT TYPE="TEXT" NAME="subBean.JSP <P> Number (subBean) <BR> <%= getErrorMessage(errorTable. if (message == null) message = "". "subBean. 130 .setString("abc").jsp: <%@ page language="java" %> <jsp:useBean id="simpleBean" scope="request" class="com.getNumber() %>"> <P> <INPUT TYPE="SUBMIT" VALUE="Submit"> <INPUT TYPE="RESET" VALUE="Reset"> </FORM> </BODY> </HTML> <%! String getErrorMessage(java. } %> ComplexHndl.number" VALUE="<%= simpleBean.Hashtable errorTable.mapping.mapping.
//* color : checkbox group %> <jsp:setProperty name="simpleBean" property="colors"/> <% if (simpleBean.length() == 0 || flagValue.setNumber(0. setErrorMessage(errorTable.setFlag(flagValue != null).equals("false")) flagValue = null. if (flagValue != null) { flagValue = flagValue. } } catch (NumberFormatException e) { simpleBean. } //* number : text try { String numberValue = request.getParameter("flag"). else { simpleBean.JSP setErrorMessage(errorTable.length() != 0) simpleBean.getInteger() == 0) { setErrorMessage(errorTable.getColors(). } //* flag : checkbox String flagValue = request. "Must be a number").length == 0) { 131 .getColors() == null || simpleBean. "number".getParameter("number"). "integer".123f). "string". setErrorMessage(errorTable. "number". if (numberValue != null && numberValue.123f).floatValue()).trim(). "Must be filled"). "An option must be selected"). } //* integer : radio group %> <jsp:setProperty name="simpleBean" property="integer"/> <% if (simpleBean. "Must be filled"). } simpleBean.11 .setNumber(new Float(numberValue).setNumber(0. if (flagValue.
string"/> <% if (simpleSubBean.setString("").11 . "Must be filled").floatValue()). setErrorMessage(errorTable. "list".getString().length == 0) { simpleBean.setList(new int[] { 2. "Must be } //* subBean. setErrorMessage(errorTable. //* subBean. "One or more colors must be selected"). 132 .getOptional() == null) simpleBean. } //* optional : text %> <jsp:setProperty name="simpleBean" property="optional"/> <% if (simpleBean.number : text try { String numberValue = request.setOptional("").length() == 0) { simpleSubBean.setNumber(new Float(numberValue).number".length() != 0) simpleSubBean.string : text %> <jsp:setProperty name="simpleSubBean" property="string" param="subBean. "One or more items must be selected"). "subBean.getParameter("subBean. "subBean.string". "colors".getList().number"). } //* list : select %> <jsp:setProperty name="simpleBean" property="list"/> <% if (simpleBean.getString() == null || simpleSubBean.JSP setErrorMessage(errorTable. else { setErrorMessage(errorTable. 3 }). if (numberValue != null && numberValue.getList() == null || simpleBean.
code=com. This class is extended by BeanDispatcher. simpleSubBean. The Java code could easily be moved to a utility class. } if (isPostMethod && errorTable.JSP filled").\ 133 . simpleBean.SimpleBean.util.7 using the framework with servlets and JSPs The SimpleHndl. simpleBean. String property. "Must be a number"). A more elegant solution is the replacement of the JSP handler with a general Java servlet.put(property.setNumber(0.Hashtable errorTable.helpers.simple.mapping package contains an abstract class called GenericHandler. simpleBean.isEmpty()) { %> <jsp:forward page="SimpleProc. which is the bean-independent equivalent of SimpleHndl.setList(new int[] { 2.setString("abc"). simpleBean. String message) { message = "<FONT COLOR=\"#FF0000\">" + message + "</FONT><BR>". } %> 11.setFlag(true).number".setString("").initparams=\ BEAN_NAME=com. 3 }). message).BeanDispatcher SimpleHndl.mapping.jsp.jsp"/> <% } %> <%! void setErrorMessage(java. The JSP handler can be replaced by only a few lines that are added to servlets.jsp"/> <% } else { %> <jsp:forward page="ComplexForm.properties or web. That was a simple and compact way to present a handler. } } else { simpleBean.setOptional("").xml: SimpleHndl. } } catch (NumberFormatException e) { setErrorMessage(errorTable.examples.123f). "subBean.11 .devsphere.devsphere.devsphere.mapping.helpers.jsp handler is basically a Java scriptlet.18. The com. errorTable.
If you have another bean-form pair.mapping.BeanDispatcher AnotherHndl.code=com. A servlet can be made bean-independent.devsphere.host. Users invoke the servlet by requesting a URL like this: http://www.ClassName There is nothing that can stop you associating many servlets with the same class.mapping.\ BASE_PATH=/simple or <servlet> <servlet-name>SimpleHndl</servlet-name> <servletclass>com.8 why using servlets? Using a JSP.host.another. you could add a few other lines to servlets.BeanDispatcher</servlet-class> <init-param> <param-name>BEAN_NAME</param-name> <paramvalue>com.examples.xml) file: ServletName. All requests to one of the declared servlets will be serviced by the same instance of the servlet class.code=com.simple.examples.host.company.com/AppName/servlet/SimpleHndl http://www.helpers. A standard servlet engine running on a single JVM will instantiate the servlet class once for each servlet declaration.helpers.SimpleBean</param-value> </init-param> <init-param> <param-name>BEAN_ID</param-name> <param-value>simpleBean</param-value> </init-param> <init-param> <param-name>BASE_PATH</param-name> <param-value>/simple</param-value> </init-param> </servlet> GenericHandler and BeanDispatcher were presented in a previous chapter. In many cases.11 . you have to provide a JSP handler for each bean. 11.AnotherBean.mapping.mapping.properties: AnotherHndl.devsphere. If your Web application contains many forms/beans. You may use the same class to declare one servlet for each bean component.com/AppName/servlet/AnotherHndl 134 .18. you have to declare the bean within a <jsp:useBean> tag. a servlet is identified with its class.com/AppName/servlet/ServletName The servlet engine associates a servlet to a class in the servlets.\ BASE_PATH=/another The two servlets that share the same code could be invoked with something like this http://www.initparams=\ BEAN_NAME=com.devsphere.\ BEAN_ID=anotherBean.JSP BEAN_ID=simpleBean.devsphere. The previous section showed how to declare a BeanDispatcher servlet.properties (or web.
2 and brings in mandatory support for Facelets as the view technology for JSF pages. built in Ajax support and built in support for bookmarking & page-load actions. JSF is a request-driven MVC web framework based on component driven UI design model.12 . buttons. released through the Java Community Process under Java Specification Request (JSR) 314.javaserver faces 12 . A set of APIs for: • • • • • • • representing UI components. like input fields.0.2 javaServer Faces Technology 2. namely • • • • • JSF HTML Tag Library JSF Core Tag Library JSTL Core Tag Library JSTL Functions Tag Library JSF Facelets Tag Library 136 . which loads the appropriate view template.0 supersedes version 1. Version 2.JAVASERVER FACES 12. A JavaServer Pages (JSP) custom tag library for expressing a JavaServer Faces interface within a JSP page. Version 2. This technology includes: 1.0 is part of the Java Enterprise Edition 6 platform. using XML files called view templates or Facelets views. and renders the response (typically HTML) to the client. 2. processes events. builds a component tree. Requests are processed by the FacesServlet.0 The latest version (as of november 2010) of JavaServer Faces technology is version 2. links UI components management events handling input validation error handling page navigation specification support for internationalization and accessibility. There are five JSF specific tag libraries defined in this specification.1 what are javaServer faces? JavaServer Faces technology is a server-side user interface component framework for Java based web applications. 12.
As of version 1.javaserver faces 12. JSP pages are compiled into servlets but it's not the case with Facelets because Facelet pages are XML compliant and its framework uses a fast SAXbased compiler to build views.12 .4 the html JSF tags This tag library contains JavaServer Faces component tags for all UIComponent + HTML RenderKit Renderer combinations defined in the JavaServer Faces specification. here is an exhaustive list of the JSF HTML tags: • • • • • • • • • • • • • column commandButton commandLink dataTable form graphicImage inputHidden inputSecret inputText inputTextArea message messages outputFormat 137 . The HTML tags can be grouped in the following categories: • • • • • • • inputs outputs commands selections layouts data table errors and messages 12.1 the list of JSF HTML Tags For reference. there are 25 HTML JSF tags. 12.2 of the JFS specification.3 facelets Facelet is a view technology for Java Server Faces (JSF) that allows building composite views more quickly and easily than with JSP which is the default view technology for JSF.4. Facelets can make changes to pages immediately so developing JSF applications with Facelets is simply faster.
description}" /> </h:column> <h:column> <f:facet name="header"> <h:outputText value="Price" /> 138 . These are rendered as a single "th" element in a row at the top of the table and as a single "td" element in a row at the bottom of the table.4.2 h:dataTable The dataTable tag renders an HTML 4. A column component is rendered as a single "td" element. footers. can be accomplished quite easily with this tag. such as alternating row colors. columns and rows. A dataTable tag can also contain header and footer facets. For more information about columns. respectively.javaserver faces • • • • • • • • • • • • outputLabel outputLink outputText panelGrid pnelGroup selectBooleanCheckbox selectManyCheckbox selectManyListbox selectManyMenu selectOneListbox selectOneMenu selectOneRadio In the next paragraphs. Example: <h:dataTable id="table1" value="#{shoppingCartBean.01 compliant table element that can be associated with a backing bean to obtain its data as well as for event handling purposes.12 . see the column tag documentation. The table can be customized extensively using cascading stylesheet (CSS) classes and definitions to enhance the appearance of the table's headers. we'll have a closer look at some of these tags.items}" var="item"> <f:facet name="header"> <h:outputText value="Your Shopping Cart" /> </f:facet> <h:column> <f:facet name="header"> <h:outputText value="Item Description" /> </f:facet> <h:outputText value="#{item. 12. The dataTable tag typically contains one or more column tags that define the columns of the table. Common formatting techniques.
00</td></tr> <tr><td>Juicy Orange</td><td>$5.total}" /> </f:facet> </h:dataTable> HTML Output <table id="table1"> <thead> <tr><th scope="colgroup" colspan="2">Your Shopping Cart</th></tr> <tr><th>Item Description</th><th>Price</th></tr> </thead> <tbody> <tr><td>Delicious Apple</td><td>$5.3 h:form The form tag renders an HTML form element. Example: <h:commandButton id="button1" value="#{bundle.00</td></tr> </tfoot> </table> 12. binding request parameters to backing bean properties. The use of the POST method is also required and it is not possible to use the GET method for forms generated by this tag. Example: <h:form id="form1"></h:form> HTML Output <form id="form1" name="form1" method="post" action="/demo/form.12 .00</td></tr> <tr><td>Tasty Melon</td><td>$5. The display value of the button can also be obtained from a message bundle to support internationalization (I18N).4 h:commandButton The commandButton tag renders an HTML submit button that can be associated with a backing bean or ActionListener class for event handling purposes.4.price}" /> </h:column> <f:facet name="footer"> <h:outputText value="Total: #{shoppingCartBean. your options include using plain HTML forms.checkoutLabel}" action="#{shoppingCartBean. and using the outputLink tag to generate dynamic hyperlinks.checkout}" /> 139 .jsp" enctype="application/x-www-form-urlencoded"></form> 12.00</td></tr> </tbody> <tfoot> <tr><td colspan="2">Total: $15.javaserver faces </f:facet> <h:outputText value="#{item. JSF forms use the "post-back" technique to submit form data back to the page that contains the form.4. If your application requires the use of the GET method for form submission.
5.user.12 .6 message Tag The message tag renders a message for a specific component.4. You can also customize the standard error messages by overriding specific JSF properties in your message bundle." /> 12. green for information) as well as the detail level of the message itself. 12. You can customize the message generated by this component by applying different CSS styles to the message depending on its severity (eg. Example: <h:inputText id="username" value="#{userBean.5 the core JSF tags The core JavaServer Faces tags define custom actions that are independent of any particular RenderKit.5 h:inputText The inputText tag renders an HTML input element of the type "text". Example: <h:inputText id="username" required="#{true}" value="#{userBean.username}" /> HTML Output <input id="form:username" name="form:username" type="text" /> 12.1 the list of JSF Core Tags Here is an exhaustive list of the JSF core tags: • • • • • • actionListener attribute convertDateTime converter convertNumber facet 140 .username}" errorStyle="color:red"/> <h:message for="username" /> HTML Output <input type="text" id="form:username" name="form:username" value=""/> <span style="color:red">"username": Value is required.</span> 12.javaserver faces HTML Output <input id="form:button1" name="form:button1" type="submit" value="Check Out" onclick="someEvent().user.4. red for error.
Example: <h:dataTable id="reportTable" value="#{reportBean. you can create a header and a footer facet for a dataTable component. The Facet tag registers a named facet on the component associated with the enclosing tag. For example. 12.12 .5.javaserver faces • • • • • • • • • • • • loadBundle param selectItem selectItems subview validateDoubleRange validateLength validateLongRange validator valueChangeListener verbatim view Some of these tags will be detailed in the next paragraphs.2 f:facet A facet represents a named section within a container component The JSF facets specify the requirements and constraints that apply to a JSF project.dailyReport}" var="item"> <h:column> <f:facet name="header"> <h:outputText value="Daily Report" /> </f:facet> <h:outputText value="#{item}" /> </h:column> </h:dataTable> HTML Output <table id="reportTable"> <thead> <tr><th>Daily Report</th></tr> </thead> <tbody> <tr><td>Item 1</td></tr> <tr><td>Item 2</td></tr> <tr><td>Item 3</td></tr> </tbody> </table> 141 .
12 . such as one of the HTML select or text input components. The body content of this tag must be empty. The JavaServer Faces framework includes three standard validators (see the validateDoubleRange. An alternative to this tag is to use a method-binding expression pointing at a value change listener method of a backing bean on the component tag itself. The ValueChangeListener interface should be implemented by classes that you want to register with components that publish value change events. and validateLongRange tags) but the Validator interface can be implemented by classes that provide custom validation for your application. Example: <h:inputText id="emailAddress" value="#{customerBean. validateLength. Notice in the example below the use of the JavaScript onchange() event to trigger form submission when the list selection changes. 12.optionList}" /> <f:valueChangeListener type="com. the user must manually submit the form to invoke the ValueChangeListener.3 f:validator The Validator tag registers a named Validator instance on the component associated with the enclosing tag.MyValueChangeListenerImpl" /> </h:selectOneMenu> HTML Output <select name="form:optionMenu" size="1" onchange="submit()"> <option value="1">Option 1</option> <option value="2">Option 2</option> <option value="3">Option 3</option> </select> 142 .4 f:valueChangeListener The ValueChangeListener tag registers a ValueChangeListener instance on the component associated with the enclosing tag. This tag accepts one value matching the validator ID you assigned to your validator class in your Faces configuration file.emailAddress}"> <f:validator validatorId="emailAddressValidator" /> </h:inputText> <h:message for="emailAddress" /> HTML Output <input id="form:emailAddress" name="form:emailAddress" type="text" value="fake@email"/> Invalid email address.5.customer.selectedOption}" onchange="submit()"> <f:selectItems value="#{optionBean. Without this JavaScript event. You can register several ValueChangeListeners with a component and they will be invoked in the order that they are registered.javaserver faces 12. Any component that receives user input.5. but only if the new input is validated successfully. can publish value change events. Example: <h:selectOneMenu id="optionMenu" value="#{optionBean.mycompany. A component fires a value change event when its input changes.
If the locale requested by the user is not supported by your application. myJSFapp 143 . the JSF framework will use the default locale specified in your Faces configuration file.jsp (English) <f:view locale="en"> <f:loadBundle basename="com. You can wrap the root element of the structured markup language used in your document with this tag to ensure that all child tags are part of the same view.mycompany.6 the structure of a JSF application Here is a typical directory structure for a JSP application.jsp (French) Bienvenue à notre site! 12. Another option is to obtain the locale dynamically through user interaction.welcomeMessage}" /> </f:view> welcome_fr.javaserver faces 12. JSF will set that locale for the view and will display the messages for that locale defined in the locale's message bundle. If your application supports the locale requested by the user. This tag is useful for internationalization (I18N) purposes. Example: welcome_en.jsp (English) Welcome to our site! welcome_fr. You can also specify the locale for which the view is to be rendered by explicitly setting the locale attribute of the view tag.welcomeMessage}" /> </f:view> HTML Output welcome_en. The locale attribute accepts a value-binding expression that could resolve to the desired locale.5 f:view The View tag is the container for all JavaServer Faces component tags used on a page. If you have not specified a default locale. for each locale you wish to support.MessageBundle" var="bundle" /> <h:outputText value="#{bundle.5. By default the JSF framework will attempt to select the best view for your user based on the Accept-Language header sent to the server from the user's browser as part of the HTTP request for your page. including images and styles. This allows you to design localized versions of each page.12 . This information could later be stored in a cookie and/or a database to identify which locale is preferred by your user. It provides you with several options for presenting your user with localized views of your application.jsp (French) <f:view locale="fr"> <f:loadBundle basename="com.MessageBundle" var="bundle" /> <h:outputText value="#{bundle.mycompany. The directory myJSFapp is the base directory of the application. JSF will use the default locale for the Java Virtual Machine serving your application.
Create properties files 144 . custom tag libraries.xml – the deployment descriptor of the application. It has a deployment descriptor.contains libraries required by the application. Let's have a look at the steps needed to build a JSF application: 1.7 how does JSF work? a first example Example taken from http://www.html.exadel.xml – the JSF configuration file.xml file /JavaSource – application specific java source classes and properties files /WebContent – contains the Web application files used by the application server or by the web container /WEB-INF – contains files used as part of the runtime Web application /classes – compiled Java classes and properties files copied from the /JavaSource directory /lib . Create JSP pages 2. The way the application behaves is controlled by an event listener class.javaserver faces /ant build. What makes it different is that a JSF application is event-driven. Define navigation rules 3. jsf-api.xml /pages Comments on this structure: • • • • • • • • • • • myJSFapp – application base directory with application name /ant – directory containing Ant build scripts with a default build. JSP pages.xml web. included in the /WEB-INF directory faces-config. mandatory for any JSF application web. static resources. like third party jar files jsf-impl. included in the /WEB-INF directory /pages – directory containing JSP and HTML presentation pages 12.xml /JavaSource /WebContent /WEB-INF /classes /lib jsf-impl. and so on.jar.jar jsf-api. Create managed beans 4. A JSF application is nothing else but a servlet/JSP application.jar – files included in the /lib directory.com/tutorial/jsf/jsftutorial-kickstart.12 .jar faces-config.
jsp files in WebContent/pages/.jsp is greeting. This file already exists in the skeleton directory structure. <navigation-rule> <from-view-id>/pages/inputname. 12. You just need to create its contents.12 . These files will act as place holders for now.1 creating JSP Pages Create the inputname. we can create a navigation rule. we just want to go from inputname.jsp.jsp. The navigation rule for this application is described in the faces-config.javaserver faces 5. Now that we have the two JSP pages.jsp to greeting.jsp and greeting. You only need to create the JSP files. The rule says that from the view (page) inputname. In our application. Create an index. Edit JSP pages 6.7. And that's all there is to this. The directory structure already exists.jsp</to-view-id> </navigation-case> </navigation-rule> 145 .2 navigation Navigation is the heart of JavaServer Faces. Compile the application 8. Deploy and run the application 12.xml file. if the "outcome" of executing inputname.jsp</from-view-id> <navigation-case> <from-outcome>greeting</from-outcome> <to-view-id>/pages/greeting. it would look something like this: Image from Exadel Studio Pro The navigation rule shown in the picture is defined below.jsp go to the view (page) greeting.jsp file 7.7. As a diagram. We will complete the content of the files a little bit later.
javaserver faces This is.3 creating the Managed Bean Next. The bean simply captures the name entered by a user after the user clicks the submit button. } /** * @param Person Name */ public void setPersonName(String name) { personName = name.xml file should look like this: 146 .) 12.3.2 declaring the Bean in faces-config. visit the JSP Navigation Example forum item.java Put this code in the file: package myJFSapp. we will create a PersonBean. The next line is the full class name.xml describes our Java bean that we created in the previous steps. request sets the bean scope in the application. public class PersonBean { String personName.3.PersonBean. This class is straight-forward.java file. a very simple navigation rule.7. This section defines a bean name PersonBean. we will create a myJFSapp folder inside the JavaSource folder.3 faces-config. <managed-bean> <managed-bean-name>personBean</managed-bean-name> <managed-bean-class>myJFSapp. It's a simple Java bean with one attribute and setter/getter methods.3.1 PersonBean.7. To read more about navigation rules. } } Later you will see how to "connect" this bean with the JSP page.12 . This way the bean provides a bridge between the JSP page and the application logic.7. /** * @return Person Name */ public String getPersonName() { return personName. (Please note that the field name in the JSP file must exactly match the attribute name in the bean.7. Inside this myJFSapp folder.xml Now. You can easily create more complex ones.xml Your final faces-config. 12. of course. myJFSapp. 12.PersonBean</managed-bean-class> <managed-bean-scope>request</managed-bean-scope> </managed-bean> 12. the second part of faces-config.
com/jsf/core" prefix="f" %> 147 . Keeping the messages separate from the JSP page allows us to quickly modify the messages without editing the JSP page. Inc.sun.properties file in the bundle folder.5.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.//DTD JavaServer Faces Config 1.7. 12.sun. We need to place it in the JavaSource folder so that during project compilation.jsp</from-view-id> <navigation-case> <from-outcome>greeting</from-outcome> <to-view-id>/pages/greeting.properties Put this text in the properties file: inputname_header=JSF KickStart prompt=Tell us your name: greeting_text=Welcome to JSF button_text=Say Hello sign=! We now have everything to create the JSP pages.1 inputname.12 .7.PersonBean</managed-bean-class> <managed-bean-scope>request</managed-bean-scope> </managed-bean> </faces-config> 12.javaserver faces <?xml version="1.4 creating a Properties File (Resource Bundle) A properties file is just a file with param=value pairs.4.1//EN" "http://java.jsp</to-view-id> </navigation-case> </navigation-rule> <managed-bean> <managed-bean-name>personBean</managed-bean-name> <managed-bean-class>myJFSapp. Let's create a bundle folder in the JavaSource/myJFSapp folder and then a messages.dtd"> <faces-config> <navigation-rule> <from-view-id>/pages/inputname. 12.5 editing the JSP Pages Two pages should already have been created in myJFSapp/WebContent/pages.jsp Put the following coding into this file: <%@ taglib uri="http://java.7. We use the messages stored in the properties file in our JSP pages. 12.1 messages.sun.7.com/dtd/web-facesconfig_1_1. this properties file will be copied to the classes folder where the runtime can find it.0"?> <!DOCTYPE faces-config PUBLIC "-//Sun Microsystems.
com/jsf/html" prefix="h" %> <%@ taglib uri="http://java. Then.personName}" required="true"> <f:validateLength minimum="2" maximum="10"/> </h:inputText> <h:commandButton action="greeting" value="#{msg.messages" var="msg"/> The first line of these three is a directive that tells us where to find JSF tags that define HTML elements and the second directive tells us where to find JSF tags that define core JSF elements.com/jsf/core" prefix="f" %> <f:loadBundle basename="myJFSapp.12 .sun. <%@ taglib uri="http://java. look up the value for inputname_header in that file and print it here. One can also add a line like <f:validateLength minimum="2" maximum="10"/> to make sure that the length of this field is reasonable long. 1 <h:form id="helloForm"> 2 <h:outputText value="#{msg.prompt}"/> 3 <h:inputText value="#{personBean.messages" var="msg"/> <html> <head> <title>enter your name page</title> </head> <body> <f:view> <h1> <h:outputText value="#{msg.bundle. The third line loads our properties file (resource bundle) that holds messages that we want to display in our JSP page.button_text}" /> </h:form> </f:view> </body> </html> Now.bundle. let's explain the important sections in this file after displaying the code for each section starting from the top.personName}" required="true"> 4 <f:validateLength minimum="2" maximum="10"/> 5 </h:inputText> 6 <h:commandButton action="greeting" value="#{msg.javaserver faces <f:loadBundle basename="myJFSapp. The required attribute of the h:inputText tag insures that an empty name will not be sent. <h:inputText value="#{msg.button_text}" /> 7 </h:form> 148 .sun.prompt}"/> <h:inputText value="#{personBean.inputname_header}"/> </h1> <h:form id="helloForm"> <h:outputText value="#{msg.inputname_header}" required="true"> This tag simply tells us to look in the resource bundle that we defined at the top of the page.
jsp page. Lines 3-5. 12.2 greeting. It uses a JSP tag to "forward" to the inputname. The first line will take a message from the resource bundle and print it on the page. Line 2.com/jsf/core" prefix="f" %> <f:loadBundle basename="myJFSapp.. Creates an HTML form using JSF tags. Line 6.sun. you will see something like this: Welcome to JSF.jsp file inside the WebContent folder.5. name! 12. Theses lines import JSF tag libraries and our properties file (resource bundle) with the messages.jsp File We will now create a third JSP file that doesn't actually function as a presentation page.12 . JSF tags for the HTML form's submit button. The button's value is being retrieved from the properties file.7.xml file. The first three lines are identical to our first page.6 creating the index. While the button's action attribute is set to greeting which matches the navigation-outcome in faces-config.messages" var="msg"/> <html> <head> <title>greeting page</title> </head> <body> <f:view> <h3> <h:outputText value="#{msg. Having an index. Once this page is displayed in a Web browser.personName}" /> <h:outputText value="#{msg.sun.javaserver faces Line 1. In the value attribute we connect (bind) this field to the managed bean attribute that we created before.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java. Note that this file is not created in the pages folder like the previous JSP files.sign}" /> </h3> </f:view> </body> </html> This page is very simple.greeting_text}" />. specifically the bean attribute personName. Create the index.. and also print its contents on the page.jsp file will allow us to start the application like this: http://localhost:8080/myJFSapp/ 149 . The second line will access a Java bean.bundle. The main code of interest to us is between the <h3>. Prints a message from the properties file using the value of prompt. That's how JSF knows where to go next. <h:outputText value="#{personBean. Creates an HTML input text box.</h3> tags.jsp Put this coding inside the second JSP file: <%@ taglib uri="http://java.7.
12.xml file within the Host element just before the closing </Host> tag. (Port 8080 is the default port in Tomcat. 12.jsp.1 Overview This is a tutorial in which we create a simple JSF application to demonstrate FacesIDE's functionality. might possibly be different). When Tomcat is done loading. 150 . you'll notice the file suffix is . put this coding into the file: <html> <body> <jsp:forward page="/pages/inputname. To do this we need to register a context in Tomcat's {TomcatHome}\conf\server.xml file for the application *.bat in Tomcat's bin directory). We will use null (link) deployment to deploy the application in-place.jsf and not .7. To build the application run the build. insert this code: <Context debug="0" docBase="Path_to_WebContent" path="/myJFSapp" reloadable="true"/> near the end of the server.jsf is the URL pattern used to signal that the forwarded page should be handled by the JavaServer Faces servlet within Tomcat.8 creating a JSF application in eclipse with the facesIDE plugin Example taken from http://amateras.xml file.sourceforge. we need to deploy it. Path_to_WebContent needs to be replaced with the exact path on your system to the WebContent folder inside the myJFSapp folder (for example.xml script from the ant folder: ant build 12. verifies the information. because in the web.7.8 Deploying Before you can run this application within the servlet container.html .7 Compiling An Ant build script is provided for you. 12. start the Tomcat server (probably using the script startup. 12.9 Running Next. which asks an user for an ID and password. Your setup. This is a "login" application.7.jp/docs/FacesIDE/SampleJSFApp.8. launch a web browser and enter: http://localhost:8080/myJFSapp.12 . Of course. and forwards the user to a success or error page. This is used here. To do this. though.javaserver faces Now.jsf" /> </body> </html> If you look at the path for the forward. C:/examples/myJFSapp/WebContent). We are almost done with this example.
click Finish 4. Enter project name. and to add JSF libraries to the project. We don't assume that a J2EE server-specific plugin. Along the way we'll use the following FacesIDE functionality: • • • • add JSF support to a project use the New JSF/JSP file wizard use the JSP Editor (see HTML/JSP/XML Editor) use the faces-config. The New Project wizard appears. select Amateras/JSF/Add JSF Support. 10. note that Root: has automatically been set to /webroot. From the menu bar select File/New/Project. and set up folders for a web application. c. 2. 7. your mileage may vary. jsf-login. in the wizard that appears. click OK to dismiss the properties dialog.xml Editor (see faces-config.. and a session-scoped managed bean to coordinate their interactions. This folder will contain all "functional" pages. click Next. a.javaserver faces The application will use a few JSP pages with JSF elements. say. select the Source tab. click Next. make sure all checkboxes are checked. see Installing & Uninstalling.WEB-INF 151 . name the folder webroot 5. Select the Amateras node. click Yes through messages that appear.. 12.. From the menubar open Project/Properties 8. name the folder pages. 9..2 Creating A Project Here we create an Eclipse project. Your folder structure should now be as follows: jsf-login | +-. Create the source folder: select the Java Build Path node. such as the Sysdeo Tomcat plugin has been installed. click Add Folder.webroot | +-..Set the output folder: in the Default output folder textbox at the bottom. from the menubar select File/New/Other. enter jsflogin/webroot/WEB-INF/classes.. and from its context menu select File/New/Folder. for Web Application Root enter /jsflogin/webroot.. in Package Explorer select the jsf-login project b. click Next d. Select Java Project. in the dialog that appears create a folder named src directly under the project folder (jsf-login). make sure HTML validation and DTD/XSD validation are enabled. The folder structure created is simply one that works for this author. 6.8. 3. Create the web root folder: in Package Explorer select the jsf-login project. and from the menubar select File/New/Folder.src | +-. make sure FacesIDE and required plugins have been installed. Use FacesIDE to add JSF support: we use a FacesIDE wizard to create J2EEprescribed folders and files in webroot. 1.12 .xml Editor) As a prerequisite for the tutorial.. Create the web pages folder: in Package Explorer select the webroot folder. in the Add JSF Support page.
The Java code editor opens. 3. public class LoginManager { private String _uid = "". for name enter mgr.LoginManager. } return action. Enter and save the following code for the LoginManager class: // LoginManager. public public public public String getUserID() { return _uid.pages 12. b. click Managed Bean. The New Java Class wizard appears. In the Package field. The faces-config. 2.java package login. for scope select 152 .3 Creating & Configuring Managed Beans Here we create a class called LoginManager which will be used as a backing bean for the login process. Click Finish. 1. In Package Explorer select the src folder.equalsIgnoreCase("bar") ) action = "loginPass". in Package Explorer select jsf-login/webroot/WEB-INF/facesconfig.equalsIgnoreCase("foo") && _pwd. if ( _uid. click Add.8.xml Editor.12 .classes (not shown in Java perspective) | | | +-. } String getPassword() { return _pwd. input widgets appear d. from its context menu select New/Class. along the bottom of the editor there are 3 tabs.javaserver faces | | | +-. We then configure it to be a managed bean.xml editor opens. else action = "loginFail".lib | +-. } void setPassword(String pwd) { _pwd = pwd. } public String loginAction() { String action = null. } 4. enter login. from its context menu select Open With/faces-config. private String _pwd = "". in the Name field enter LoginManager. a. Use FacesIDE to configure the bean: we use a FacesIDE editor to configure LoginManager as a session-scoped managed bean.xml. } void setUserID(String uid) { _uid = uid. for class enter login. c.
jsp). make sure that the parent folder is set to /jsflogin/webroot.webroot/index.webroot/pages/success. the New File wizard appears.jsp. We will have 4 pages: a start page (index. for File name enter index. b.jsp: create this file similarly to index. using the Workbench's standard file-creation facilities.8.jsp).jsp are simple pages with static content.jsp and error.jsp.jsp" /> </body> </html> 2. Then we create login. click Finish. Create error. save the file and close the editor. Content pages are placed in webroot/pages. again. e.javaserver faces session. and 3 content pages (login. Enter the following code: <!-. then close the editor 12. </body> Please try 153 .12 .webroot/pages/error. Create index. c. 1. enter the following code. so we create them first. success. but in webroot/pages. from its context menu select New/File.jsp. and its sole function is to forward users to the login page. Enter the following code: <!-. <!-. the JSP Editor opens.jsp: create this file similarly to index.jsp --> <html> <body> <jsp:forward page="faces/pages/login. index. from the menubar select File/Save.jsp --> <html> <head> <title>jsf-login</title> </head> <body> <h2>Success!</h2> </body> </html> 3. All pages except login.jsp: a.jsp is placed directly in webroot.jsp.4 Creating JSP Pages Here we create the JSP pages that make up the application's user interface.jsp --> <html> <head> <title>jsf-login</title> </head> <body> <h2>Error!</h2> The user-id and or password were invalid. in Package Explorer select webroot.jsp using a FacesIDE wizard. but in webroot/pages. Create success.
etc. Note: the JSP editor is aware of referenced tag libraries. Open the JSF palette... charset=Cp1252" %> <%@ taglib uri="http://java.12 . and the JSP Editor can help with code. for File name enter login. create a few blank lines between the <h:form> elements. this inserts the corresponding JSF element at the cursor location..com/jsf/html" prefix="h" %> <%@ taglib uri="http://java. and hit CTRL + Spacebar. you would get a popup window of JSF HTML elements. a code-completion window pops up. place your cursor in one of these lines. and that Use MyFaces Tomahawk components and Use MyFaces SandBox components are unchecked.sun. 154 . Thus if you were to type <h: and hit CTRL + Spacebar.sun. place the cursor inside the <h:inputText> element. the FacesIDE JSP Editor opens.javaserver faces </html> 4. with the following template code. the New wizard appears. select Amateras/JSF/Faces JSP File. charset=Cp1252"/> <title></title> </head> <body> <f:view> <h:form> </h:form> </f:view> </body> </html> We will now edit this page to contain our input widgets. click Next c. To see this in action.jsp. make sure that Container is set to /jsflogin/webroot/pages. click Finish.jsp: a. place the cursor between the <title></title> elements. as shown below.com/jsf/core" prefix="f" %> <html> <head> <meta http-equiv="Content-Type" content="text/html. now we want to add attributes to this element. b. from its context menu select New/Other. and dock it along the right. in Package Explorer select webroot/pages. and uses them for code completion as well. Create login. (See Show View Dialog) f. expand the JSF HTML panel in the palette.completion. enter jsf-login e. d. and choose default for Template. <%@ page contentType="text/html. and click on the icon for <h:inputText>. g.
insert a <h:commandButton> element. in the code-completion window scroll down to value. this inserts value="" at the cursor. complete the expression with the closing { k.javaserver faces h.sun. This is shown below: (Recall that we configured LoginManager as a managed bean called mgr.password}" l. set its value binding expression to value="#{mgr. place the cursor between the quotes in value="". with the barest presentational formatting. insert another <h:inputText> element.com/jsf/core" prefix="f" %> <html> 155 . select userID from the code-completion window. and hit Enter. is shown below: <%@ page contentType="text/html. charset=Cp1252" %> <%@ taglib uri="http://java.sun. a code-completion window pops up..com/jsf/html" prefix="h" %> <%@ taglib uri="http://java. and its action to the value binding expression #{mgr.loginAction} The final code. set its value to Login.12 . enter #{mgr. with bean properties available in mgr. i.) j. and hit CTRL + Spacebar. FacesIDE can provide code completion here as well. We will now bind this to the userID property of LoginManager.
and the page's properties appear in the Workbech's Properties view.xml Editor.5 Creating Navigation Rules Here we create navigation rules among pages.userID}"/> <br/>Password: <h:inputText value="#{mgr. Open faces-config.javaserver faces <head> <title>jsf-title</title> </head> <body> <f:view> <h:form> UserID: <h:inputText value="#{mgr. 1. from the Navigation panel in the palette at left. Select the Navigation tab 3. 2.12 .8.loginAction}"/> </h:form> </f:view> </body> </html> 12. 156 . it should open in the faces-config. Note that the icon has a small triangle overlay--this indicates that something is wrong. this inserts a page icon into the editor.xml. This is shown below.password}"/> <br/><h:commandButton value="Login" action="#{mgr. using a FacesIDE editor. then click inside the editor window. click on Page.
"Decharge" the mouse pointer by clicking on the pointer icon in the palette. select Navigation Case. notice that the warning triangle disappears.12 . then click on the newly-added forward-action icon to select it.jsp and then on the icon for success. Arrange them as shown below: Now we'll add navigation rules among the pages. 6. This inserts a forward-action between the two pages.jsp 4. You can also change it on the diagram directly (select the page and click once more).jsp. Its properties appear in the Properties view. change the value of path to /index.jsp and /pages/error.jsp. 5.jsp. in the Properties view. then click first on the icon for login.jsp. and is represented by an arrow. /pages/success. This is shown below: 157 . add 3 more pages. from the palette at left.javaserver faces specifically that FacesIDE could not locate a page at path /page1. and set them to /pages/login.
scroll to the bottom and look for the comment <!-. Deployment to some servers is described below: 158 . We want virtual path-based mapping.xml is indicate the Faces Servlet mapping.jsp to error. and extension-based mapping is turned on. open web.jsp. As it turns out. any other id/password should send you to the error page. and you should be automatically forwarded to login. by default virtual path-based mapping is commented out. Once deployed browse to index. The application is now complete. and you should be able to deploy it to your server of choice.jsp.xml.jsp. 12. and we'll then be ready to deploy the application. so uncomment it. You can also change values by direct-editing (select once and re-click) in the diagram 8.12 . Use UserID/Password of foo/bar.xml. all we need do in web. since we have such a trivial application.xml for the specifics of our application. or leave it as-is. and you should be sent to the success page. 1. You may comment out the entry for extension-based mapping.6 Editing web. and set its fromoutcome to loginFail We're done with setting up navigation rules.8. Similarly add a forward-action from login. in the Properties view (or direct editing on the diagram).Faces Servlet Mapping --> 2. Recall that this is the success-value returned by LoginManager's loginAction method.javaserver faces 7.xml Here we edit web. change the value of fromoutcome to loginPass. We'll set some properties in web.
faces. leave XML Configuration File URL blank.convert javax.faces. Items are listed in order of decreasing search precedence: • • If the JavaServer Faces configuration file bundled into the WEB-INF directory of the webapp contains a factory entry of the given factory class name.component.7 Deploying To Tomcat 5.9 packges in the JavaServer Faces API The classes and interfaces of the JavaServer Faces API are grouped in several packages.lifecycle javax. for WAR or Directory URL enter the path to webroot. click Deploy 3.0 1.. as file:///.javaserver faces 12.render javax.CONFIG_FILES 159 . open its Manager application in a browser.el javax.faces.faces. 12.html javax.faces.8.faces.faces.faces.faces. start Tomcat. If the JavaServer Faces configuration files named by the javax. Click on its link to launch the application. we'll deploy our app by providing its directory.faces javax.faces. that factory is used.validator javax.event javax.12 .faces.faces.faces.application javax. the default URL for this is http://localhost:8080/manager/html 2. namely: • • • • • • • • • • • • • javax. For a given factory class name.context javax.. the Manager application should reload. for Context path enter /jsf-login.10 the javax.component javax. scroll down to Deploy. a corresponding implementation class is searched for based on the following algorithm.model javax.faces package Contains 2 classes – FactoryFinder and FacesException public final class FactoryFinder extends Object FactoryFinder implements the standard discovery algorithm for all factory objects specified in the JavaServer Faces APIs..webapp 12. and you should see /jsf-login in the list of running applications.
directs the process of saving and restoring the view between requests.a factory object that creates (if needed) and returns Application instances.Provides a simple implementation of StateManager that can be subclassed by developers wishing to provide specialized behavior to an existing StateManager instance. StateManagerWrapper . and supporting internationalization and accessibility.Severity . • • public class FacesException extends RuntimeException This class encapsulates general JavaServer Faces exceptions. with the last one taking precedence. The default implementation of all methods is to call through to the wrapped StateManager. its first line is read and assumed to be the name of the factory implementation class to use. • If there are any JavaServer Faces configuration files bundled into the META-INF directory of any jars on the ServletContext's resource paths. the factory entries of the given factory class name in those files are used. as well as alternative strategies for saving and restoring the state of each view.application package Contains the following classes: • Application . If none of the above steps yield a match. ViewHandlerWrapper .Provides a simple implementation of ViewHandler that can be • • • • • • • • 160 . A FacesMessage instance may be created based on a specific messageId. which is typically associated with a particular component in the view. If a META-INF/services/{factory-class-name} resource is visible to the web application class loader for the calling application (typically as a result of being present in the manifest of a JAR file). NavigationHandler – An object of this type is passed the outcome string returned by an application action invoked for this application. 12.represents a single validation (or other) message.11 the javax. ApplicationFactory . handling events and input validation. StateManager . This allows for implementations to support different response generation technologies.faces. those factories are used. the JavaServer Faces implementation specific class is used.javaserver faces ServletContext init parameter contain any factory entries of the given factory class name. and will use this (along with related state information) to choose the view to be displayed next. FacesMessage. Implementations of JavaServer Faces must provide at least a default implementation of Application.used to represent message severity levels in a typesafe enumeration. defining page navigation. FacesMessage . with the last one taking precedence.the pluggablity mechanism for allowing implementations of or applications using the JavaServer Faces specification to provide their own handling of the activities in the Render Response and Restore View phases of the request processing lifecycle.A set of APIs for representing UI components and managing their state.12 . ViewHandler .
Here they are: • • UIColumn .12 the javax. and support conversion between String and the model tier data's native data type. • ViewExpiredException .a convenience base class that implements the default concrete behavior of all methods defined by UIComponent. NamingContainer . StateHolder . UIComponentBase . String.an interface that must be implemented by any UIComponent that wants to be a naming container. 12.interface implemented by classes that need to save their state between requests. The set of UIComponent instances associated with a particular request and response are organized into a component tree under a UIViewRoot that represents the entire content of the request or response. including ValueChangeEvents and Validators.faces.a UIComponent that represents a user interface component which.restoreView(javax. triggers an application specific "command" or "action". • • 161 . The default implementation of all methods is to call through to the wrapped ViewHandler.an extension of ValueHolder that describes additional features supported by editable components.javaserver faces subclassed by developers wishing to provide specialized behavior to an existing ViewHandler instance. ContextCallBack . when activated by the user.faces. as well as access data in the model tier via a value binding expression.a UIComponent that represents a single column of data within a parent UIData component. Such a component is typically rendered as a push button. The difference is the type of this property is a MethodExpression rather than a MethodBinding. a menu item.an interface that may be implemented by any concrete UIComponent that wishes to support a local value. or a hyperlink. EditableValueHolder .FacesContext. String) results in failure on postback. ValueHolder . including the ability to invoke application actions via the default ActionListener mechanism. UIComponent . ActionSource2 . • • • • • • The classes in this package are all UI related. UICommand . The interfaces defined in this package are: • ActionSource . This allows the ActionSource concept to leverage the new Unified EL API.an interface that may be implemented by any concrete UIComponent that wishes to be a source of ActionEvents.A simple callback interace that enables taking action on a specific UIComponent (either facet or child) in the view while preserving any contextual state for that component instance in the view.component package Defines both a set of interfaces and classes.extends ActionSource and provides a JavaBeans property analogous to the "action" property on ActionSource.12 .context.implementations must throw this FacesException when attempting to restore the view StateManager.the base class for all user interface components in JavaServer Faces.
a component that may be nested inside a UISelectMany or UISelectOne component. During iterative processing over the rows of data in the data model.a UIComponent that has a value.faces.a UIComponent that represents a single boolean (true or false) value. This component has no rendering. UISelectBoolean . UIInput . and causes the addition of a SelectItem instance to the list of available options for the parent component. UIOutput . optionally retrieved from a model tier bean via a value binding expression. it is for display purposes only. • • • • • • • • • • • • • • 12.a UIComponent that supports data binding to a collection of data objects represented by a DataModel instance.The renderer for this component is responsible for obtaining the messages from the FacesContext and displaying them to the user. it is for display purposes only. UIMessage .the UIComponent that represents the root of the UIComponent tree. which is the current value of this component itself (typically established via a ValueBinding). The user cannot manipulate this component. UIPanel . by storing it as the value property of the component. The user can modify the selected value.a UIComponent that represents an input form to be presented to the user.a UIComponent that represents a component that both displays output to the user (like UIOutput components do) and processes request parameters on the subsequent request that need to be decoded. UISelectMany . The user can modify the selected values.12 .This component is responsible for displaying messages for a specific UIComponent. UISelectItem . UIMessages .a UIComponent that manages the layout of its child components. It is most commonly rendered as a checkbox. the component can be preconfigured with a currently selected item.html package 162 . the component can be preconfigured with zero or more currently selected items. Optionally. UIViewRoot .component. it just serves as the root of the component tree. that is displayed to the user. UIParameter . the object for the current row is exposed as a request attribute under the key specified by the var property. UIForm . UINamingContainer .a UIComponent that displays a graphical image to the user.13 the java. UISelectOne . by storing them as an array in the value property of the component.a UIComponent that represents an optionally named configuration parameter for a parent component. Optionally. identified by a clientId.a UIComponent that represents the user's choice of a zero or more items from among a discrete set of available options.This component is generally rendered as a select box or a group of checkboxes.javaserver faces • UIData .a UIComponent that represents the user's choice of zero or one items from among a discrete set of available options. UIGraphic . and whose child components represent (among other things) the input fields to be included when the form is submitted.a convenience base class for components that wish to implement NamingContainer functionality. The user cannot directly modify the rendered value.
an interface describing an adapter to an underlying output mechanism for binary output.14 the java. and the rendering of the corresponding response. • • • • • • 12. this class allows JavaServer Faces based applications to run in either a Servlet or a Portlet environment.contains all of the per-request state information related to the processing of a single JavaServer Faces request.represents a multiple-selection component that is rendered as a set of HTML input elements of type checkbox. It is passed to. HtmlSelectOneMenu .allows the Faces API to be unaware of the nature of its containing application environment. ResponseWriter . HtmlSelectOneListbox . FacesContextFactory .15 the java. HtmlSelectOneRadio . HtmlSelectManyListbox . ResponseStream . HtmlSelectManyMenu . ResponseWriterWrapper .context package Contains the following classes: ExternalContext .represents a multiple-selection component that is rendered as an HTML select element.convert package 164 . • • • • 12. and potentially modified by.an abstract class describing an adapter to an underlying output mechanism for character-based output. initialized for the processing of the specified request and response objects.javaserver faces property.12 .faces.a factory object that creates (if needed) and returns new FacesContext instances. showing either all available options or the specified number of options. showing a single available option at a time.represents a single-selection component that is rendered as an HTML select element.provides a simple implementation of ResponseWriter that can be subclassed by developers wishing to provide specialized behavior to an existing ResponseWriter instance.represents a single-selection component that is rendered as a set of HTML input elements of typeradio. The default implementation of all methods is to call through to the wrapped ResponseWriter.represents a single-selection component that is rendered as an HTML select element. • • HtmlSelectManyCheckbox . showing either all available options or the specified number of options. FacesContext .represents a multiple-selection component that is rendered as an HTML select element. In particular. each phase of the request processing lifecycle. showing a single available option at a time.faces.
Classes: MethodBinding . 12.1 the interface Converter Converter is an interface describing a Java class that can perform Object-to-String and Stringto-Object conversions between model data objects and a String representation of those objects that is suitable for rendering. The classes implementing this interface within this package are: • • • • • • • • • • • • • BigDecimalConverter BigIntegerConverter BooleanConverter ByteConverter CharacterConverter DateTimeConverter DoubleConverter EnumConverter FLoatConverter IntegerConverter LongConverter NumberConverter ShortConverter The package also contains one exception: • ConverterException . ValueBinding .12 . to indicate that the requested conversion cannot be performed.16 the java. • • • • 165 .an exception thrown by the getAsObject() or getAsText() method of a Converter.represents a pluggable mechanism for resolving a top-level variable reference at evaluation time. VariableResolver .an object that can be used to call an arbitrary public method.represents a pluggable mechanism for accessing a "property" of an underlying Java object instance.15.an object that can be used to access the property represented by an action or value binding expression. on an instance that is acquired by evaluatng the leading portion of a method binding expression via a ValueBinding.javaserver faces 12. PropertyResolver .el package Contains classes and interfaces for evaluating and processing reference expressions.faces.
17 the java.typesafe enumeration of the legal values that may be returned by the getPhaseId() method of the FacesEvent interface. ValueChangeEvent .represents the activation of a user interface component (such as a UICommand). • • • • • One exception .an exception reporting a syntax error in a method binding expression or value binding expression. ValueChangeListener . PhaseListener . FacesListener . • • • • Classes: ActionEvent .AbortProcessingException .a notification that the local value of the source component has been change as a result of user interface activity.thrown by event listeners to terminate the processing of the current event. PhaseId . for the request encapsulated by the specified FacesContext.listener interface for receiving ActionEvents. PhaseEvent .12 .event package Contains interfaces describing events and event listeners. and event implementation classes.an exception reporting an error that occurred during the evaluation of an expression in a MethodBinding or ValueBinding. PropertyNotFoundException . Interfaces: ActionListener .faces.a generic base interface for event listeners for various types of FacesEvents.listener interface for receiving ValueChangeEvents. ReferenceSyntaxException . • • • • 12.interface implemented by objects that wish to be notified at the beginning and ending of processing for each standard phase of the request processing lifecycle.represents the beginning or ending of processing for a particular phase of the request processing lifecycle. MethodNotFoundException .an exception caused by a method name that cannot be resolved against a base object.the base class for user interface and application events that can be fired by UIComponents.an exception caused by a property name that cannot be resolved against a base object. 166 .javaserver faces Exceptions: EvaluationException . FacesEvent .
converts the internal representation of UIComponents into the output stream • 167 .18 the java. Renderer .a convenience implementation of DataModel that wraps an array of Java objects.an abstraction around arbitrary data binding technologies that can be used to adapt a variety of data sources for use by JavaServer Faces components that support per-row processing for their child components (such as UIData). SelectItem .represents a single item in the list of supported items associated with a UISelectMany or UISelectOne component.faces. Classes: ArrayDataModel .a convenience implementation of DataModel that wraps a JSTL Result object. SelectItemGroup . DataModel .model package Contains the interface DataModelListener and several classes providing standard model data beans for JavaServer Faces. 12.19 the java.12 .lifecycle package This package contains 2 classes.a convenience implementation of DataModel that wraps an individual Java object. DataModelEvent . ListDataModel . The Lifecycle class manages the processing of the entire lifecycle of a particular JavaServer Faces request.javaserver faces 12. typically representing the results of executing an SQL query via JSTL tags.a subclass of SelectItem that identifies a set of options that will be made available as a subordinate "submenu" or "options list".represents an event of interest to registered listeners that occurred on the specified DataModel.faces. Note that the specified ResultSet MUST be scrollable.render package Contains classes defining the rendering model.a convenience implementation of DataModel that wraps an List of Java objects. ScalarDataModel . ResultSetDataModel . depending upon the requirements of the UISelectMany or UISelectOne renderer that is actually used. ResultDataModel .faces.20 the java. • • • • • • • • • 12.a convenience implementation of DataModel that wraps a ResultSet of Java objects. The LifecycleFactory class is a factory object that creates (if needed) and returns Lifecycle instances.
ResponseStateManager .represents a collection of Renderer instances that. together. • RenderKit . RenderKits are specialized for some combination of client device type. and concrete tag implementations for core tags. as well. and concrete validator implementation classes.javaserver faces (or writer) associated with the response we are creating for a particular request. LongRangeValidator .a Validator that checks the value of the corresponding component against specified minimum and maximum values LengthValidator . and advertises a set of render-dependent attributes that it recognizes for each supported UIComponent.a Validator that checks the value of the corresponding component against specified minimum and maximum values. A Validator implementation is a class that can perform validation (correctness checks) on a EditableValueHolder. including a standard servlet.12 . and/or user Locale. ConverterTag .webapp package Contains classes required for integration of JavaServer Faces into web applications. Typically. if the component does not already contain an attribute with the same name. Each Renderer knows how to render one or more UIComponent types (or classes). which perform the actual rendering process for each component. • • 12. 12. RenderKitFactory . Implementations of JavaServer Faces must provide at least a default implementation of RenderKit.22 the java.faces.Tag implementation that adds an attribute with a specified name and String value to the component whose tag it is nested inside. A ValidatorException is an exception thrown by the validate() method of a Validator to indicate that validation failed. Implementation classes: • • • DoubleRangeVlidator . know how to render JavaServer Faces UIComponent instances for a specific client.faces. AttributeTag .the helper class to StateManager that knows the specific rendering technology being used to generate the response. markup language.a Validator that checks the number of characters in the String representation of the value of the associated component. A RenderKit also acts as a Factory for associated Renderer instances. base classes for JSP custom component tags.validator package Interface defining the validator model.a factory object that registers and returns RenderKit instances.21 the java.a base class for all JSP custom actions that create and register a Converter instance on the ValueHolder associated with our most immediate • • 168 . The package contains an exception.
the JSF life cycle must ensure that the view is correct before rendering the view. User actions in JSF-generated views take place in a client that does not have a permanent connection to the server. Also. the life cycle is more complicated. but basically. related to a UIComponent. or when an exception occurs. A JSP page source is compiled into a page implementation class. the controller is the 169 .the base class for all JSP custom actions that correspond to user interface components in a page that is rendered by JavaServer Faces. Likewise. The page class processes the request and then writes the response back to the client. which passes the request to the page class.23 the JSF lifecycle Regardless of whether you are using JSF with JSP pages. you can also have a non-JSF request that generates a non-JSF response. You can have a request that comes from a previously rendered JSF page (a JSF request) and a request that comes from a non-JSF page (a non-JSF request). the controller sends a message to the model. FacetTag . When the user takes some action with the presentation.javaserver faces surrounding instance of a tag whose implementation class is a subclass of UIComponentTag. • • • • • FacesServlet . that need to process their tag bodies.the JSP mechanism for denoting a UIComponent is to be added as a facet to the component associated with its parent. you can have a JSF response or a non-JSF response. a small set of classes processes a request and sends back a response. the process includes a few more components or pages. telling the model to update its data. ValidatorTag . The JSF life cycle must handle this delay between event and event processing. In JSF. telling the view to update its presentation.12 . the JSF life cycle does not apply.a base class for all JSP custom actions. Several kinds of request/response cycles can occur in a JSF-enabled application. the model is composed of business objects that are usually implemented as JavaBeans. the controller sends a message to the view. which has several implications. To ensure that the business state is never invalid. In MVC. or some other web technology. that request is passed to the container. UIComponentBodyTag . 12. When the model is updated.a base class for all JSP custom actions that create and register a Validator instance on the EditableValueHolder associated with our most immediate surrounding instance of a tag whose implementation class is a subclass of UIComponentTag. the presentation of data (the view) is separate from its representation in the system (the model). We are concerned with these three request/response pairs: • • • Non-JSF request generates JSF response JSF request generates JSF response JSF request generates non-JSF response Of course. The delivery of user actions or page events is delayed until a new connection is established. When using JSF. UIComponentTag .a servlet that manages the request processing lifecycle for web applications that are utilizing JavaServer Faces to construct the user interface. the JSF system includes a phase for validating inputs and another for updating the model only after all inputs pass validation. When a web server receives a request. This is because the core of JSF is the MVC pattern. servlets. each request/response flow that involves JSF follows a certain life cycle. JSP pages have a relatively simple life cycle. When other pages are included or the request is forwarded. Because this does not involve JSF in any way.
any events that were generated during previous phases and that have not yet been handled are passed to the web application so that it can complete any other processing of the request that is required. In addition. This is because if the JSF implementation began to update the business objects as data was validated. Data for some components. • Render Response: The response UI components are rendered. the thread of execution for a request/response cycle can flow through each phase. the JSF implementation must create the view. As with the previous phase. In addition. However. and the UI components are the view. is validated at this time. from cookies sent as part of the request. or from request headers. • Update Model Values: After all validations are complete. such as components that create HTML input fields. For a JSF-enabled application. It updates only the UI components with the new data. and the response is sent to the client. If this is a subsequent request. if any of the data needs to be converted to a different format to update the model (for example. the JSF implementation restores the objects and data structures that represent the view of the request. Data can come from input fields in a web form. and what happens during the processing and response. not every request will flow through all six phases. and the state of the UI view is saved for subsequent requests. • Invoke Application: During this phase. the action method of any command button or link that was activated is called. Note that this does not yet update the business objects that compose the model. When a JSF implementation creates and renders a JSFenabled page. the conversion occurs in this phase. the business objects that make up the application are updated with the validated data from the request. the model would be partially updated and in an invalid state. and a piece of data failed validation. The state of the UI components is saved so that the component tree can be restored when the client sends another request. These objects update their state with the data values. depending on the request. • Apply Request Values: Any data that was sent as part of the request is passed to the appropriate UI objects that compose the view. in the order listed here and as shown in the figure below. The components are stored in a component tree. Conversion is needed when the data type of a property is not a String or a Java primitive. 170 . • Process Validations: The data that was submitted with the form is validated (if it was not validated in the previous phase). converting a String to a Date object). If this is the client's first visit to a page.12 . The JSF life cycle has six phases as defined by the JSF specification: • Restore View: In this phase.javaserver faces JSF implementation. this does not yet update the business objects in the application. the saved UI view is retrieved for the processing of the current request. it creates UI objects for each view component.
skipping any remaining phases. the flow of execution can exit the life cycle without completing further phases. you can see a number of optional paths through the life cycle. If data fails validation in either the Apply Request Values or Process Validations phase. if at any point in the life cycle the request processing is complete and a non-JSF response is to be sent to the client. the flow of execution transfers immediately to the Render Response phase. Also. information about the error is saved and processing proceeds directly to the Render Response phase. 171 . if errors occur during any of the phases.javaserver faces In the above figure. One way this might occur is if input data is incorrect or invalid.12 . For example.
sun.Wiz.2. A naming service allows you to look up an object given its name. The DNS entry Wiz.COM. naming and directory services using a common API. applications based on Java technology can store and retrieve named Java objects of any type. NDS. A naming service's primary function is to map people-friendly names to objects.48. /usr/hello.COM. c:\bin\autoexec. JNDI is also defined independent of any specific naming or directory service implementation. names an entry with the name Wiz in the COM entry.bat) to a file handle that a program can use to access the contents of the file. It is designed especially for the Java platform using Java's object model.9.2 naming concepts A fundamental facility in any computing system is the naming service--the means by which names are associated with objects and and objects are found based on their names. with each component in the path separated from left to right using the forward slash character ("/"). relative to the DNS entry Wiz. This enables Java technology-based applications to take advantage of information in a variety of existing naming and directory services. such as associating attributes with objects and searching for objects using their attributes. or objects typically used by computer programs.1 names To look up an object in a naming system. the Internet Domain Name System (DNS) maps machine names (such as www. 13. It enables applications to access different.JNDI 13 . for example. such as addresses. The naming system determines the syntax that the name must follow. The DNS naming convention calls for components in the DNS name to be ordered from right to left and delimited by the dot character (". such as LDAP. DNS.5). 13. you must provide the name of the recipient to whom you want to send mail. For example.13 . which is located in the root of the file system. possibly multiple. and NIS(YP). The UNIX pathname. To access a file in the computer. Thus the DNS name sales. JNDI provides methods for performing standard directory operations. For example. A file system maps a filename (for example. you supply it the name of the object. Different naming and directory service providers can be plugged in seamlessly behind this common API. as well as enabling the applications to coexist with legacy software and systems. the UNIXTM file system's naming convention is that a file is named from its path relative to the root of the file system.com) to IP addresses (such as 192. in turn.").JNDI 13. identifiers. In addition. This syntax is sometimes called the naming system's naming convention. Using JNDI. names a file hello in the file directory usr. 172 . When using almost any computer program or system.COM names a DNS entry with the name sales. you are always naming one object or another.1 what is JNDI? JNDI is an API specified in Java technology that provides naming and directory functionality to applications written in the Java programming language. For example. These two examples also illustrate the wide range of scale at which naming services exist--from naming an object on the Internet to naming a file on the local file system. when you use an electronic mail system. you must supply its name.
which in turn. an airplane object reference might contain only its flight number and departure time. such as COM. an airplane object might contain a list of the airplane's passengers and crew. is accessed using a file reference. By contrast. That is. The LDAP has the further rule that each component of the name must be a name/value pair with the name and value separated by an equals character ("="). that is. they must be stored by reference. a DNS domain. o=Sun. on the other hand. for example. the DNS domain Sun is a subcontext of COM. For example. and its flight number and departure time."). that is. for example. Every context has an associated naming convention. a pointer or reference to the object is placed inside the naming service. Thus the LDAP name cn=Rosanna Lee.c=us. Typically. A context provides a lookup (resolution) operation that returns the object and may provide operations such as those for binding names. such as its print server name and printing protocol. 173 . it is a much more compact representation that can be used to communicate with the object. a file directory. Finally.2. a copy of the object cannot be placed inside the naming service. some objects cannot be stored directly.JNDI The Lightweight Directory Access Protocol (LDAP) naming convention orders components from right to left. For simplicity. An LDAP name is bound to an LDAP entry.2. A printer object reference. For example. an LDAP entry. The DNS contains bindings that map machine names to IP addresses.2.4 context A context is a set of name-to-object bindings. Although in general a reference can contain any arbitrary information. For example.13 . A file directory named relative to another file directory is a subcontext (some UNIX users refer to this as a subdirectory).2 bindings The association of a name with an object is called a binding. For example. while the object itself might contain more state information.3 references and addresses Depending on the naming service. Using the reference. such as /usr. in the an LDAP entry o=sun. In another example. A printer object. might contain the state of the printer. 13. A file object.COM. a file name is bound to a file. in the UNIX file system is a context. you can contact the object and obtain more information about the object. A reference is information about how to access an object. 13. such as c=us. and fuel and instrument status. in the DNS domain Sun. The reference is a much more compact representation of information about the airplane object and can be used to obtain additional information. Instead. also called a file handle. 13. its flight plan. it is useful to refer to its contents as addresses (or communication end points): specific information about how to access the object. is a context. this tutorial uses "object" to refer to both objects and object references when a distinction between the two is not required. the directory bin is a subcontext of usr. and listing bound names. c=US names an LDAP entry cn=Rosanna Lee. the entry o=sun is a subcontext of c=us. such as its current queue and the amount of paper in the paper tray. in a file directory /usr/bin. relative to the entry o=Sun. An LDAP entry named relative to another LDAP entry is a subcontext. A name in one context object can be bound to another context object (called a subcontext) that has the same naming convention. delimited by the comma character (". unbinding names. might contain only information on how to reach the printer. is relative to c=us. is a context. For example. A DNS domain named relative to another DNS domain is a subcontext.
For example. identify a web application with its root directory (a node in the file system directory tree). because we can. Going now back to the rationality of this chapter. The DNS namespace contains names of DNS domains and entries. a name is unique 13. two different computer 174 . remember that a naming serviced associates names with real objects (resources). The computer's directory service is much more powerful.2. resolution. The LDAP namespace contains names of LDAP entries. An attribute identifier is a token that identifies an attribute independent of its values. For example. It maps a subscriber's name to his address and phone number. postal mail address. For example. various telephone numbers. you not only can look up an object by its name but also get the object's attributes or search for the object based on its attributes. A file system offers a naming service that maps filenames to files and directories. the UNIX file system has a namespace consisting of all of the names of files and directories in that file system. A namespace is the set of names in a naming system. programs. a system that implements the DNS is a naming system. a person. or a network. and color. An attribute has an attribute identifier and a set of attribute values. And it kind of makes sense. This association between a name Which leads to a list of constraints: • within a given context. An example is the telephone company's directory service. to represent a printer.1 attributes A directory object can have attributes.3 directory services Many naming services are extended with a directory service.5 naming systems and namespaces A naming system is a connected set of contexts of the same type (they have the same naming convention) and provides a common set of operations. and computer account information. A directory object can be used.13 . a printer might be represented by a directory object that has as attributes its speed. A user might be represented by a directory object that has as attributes the user's e-mail address. a computer. Thus. A naming system provides a naming service to its customers for performing naming-related operations. The LDAP offers a naming service that maps LDAP names to LDAP entries. the DNS offers a naming service that maps machine names to IP addresses. 13. in a first and raw approximation as a node in one of these trees. A directory object contains attributes that describe the object that it represents. A directory service associates names with objects and also allows such objects to have attributes. for example. one context can be viewed. and even the computer itself and other computers.JNDI If we imagine all the resources available for us as a collection of rooted trees.3. A computer's directory service is very much like a telephone company's directory service in that both can be used to store information such as telephone numbers and addresses. however. A naming service is accessed through its own interface. 13. A system that communicates using the LDAP is a naming system. A directory object represents an object in a computing environment. For example. to some extent. because it is available online and can be used to store a variety of information that can be utilized by users. For example.
can use the directory in the traditional way. And a Java calendar program can use it to retrieve user preference settings. such as that relating to machines. Network Information Service (NIS) is a directory service available on the Solaris operating system for storing system-related information. As the use of the Java programming language to write practical applications in a network environment increases. By using a directory service. for example. such as the file and print services. 13. the ability to access directory services will become essential. like any other program running on the network. might contain group objects that might in turn contain person objects. the LDAP arranges all directory objects in a tree. and users. 13. you can simplify applications and their administration by centralizing the storage of shared information. When you search. The directory service searches for and returns the objects that satisfy the search filter. Similarly. The service is accessed through its own interface. Many examples of directory services are possible.JNDI accounts might have a "mail" attribute. When directory objects are arranged in this way. might have an attribute identifier of "mail" and the attribute value of "john. such as those based on the LDAP. for example. The email address. they play the role of naming contexts in addition to that of containers of attributes. printers.13 . an organization object. and modifying the attributes associated with objects in a directory. for example.3 searches and search filters You can look up a directory object by supplying its name to the directory service.3. adding. 13. called a directory information tree (DIT). A Java mail transfer agent program can use it to retrieve mail routing information.3. to store and retrieve attributes of directory objects.113. For example.com". "mail" is the attribute identifier. 13. support the notion of searches. A directory service is a service that provides operations for creating. 175 .smith@somewhere. Within the DIT. Directory-enabled Java applications and applets. that is. 13. For example. you can query it to find all machines whose IP address starts with "192. you can query the directory service to find all users that have the attribute "age" greater than 40 years. The Novell Directory Service (NDS) is a directory service from Novell that provides information about many networking services.4 directory-enabled java applications Directory service is a vital component of network computing. networks. A Java mail client program. This style of searching is sometimes called reverse lookup or content-based searching. Alternatively. removing.3.2 directories and directory services A directory is a connected set of directory objects. you can supply not a name but a query consisting of a logical expression in which you specify the attributes that the object or objects must have. An attribute value is the contents of the attribute. The SunONE Directory Server is a general-purpose directory service based on the Internet standard LDAP. can use the directory as an address book for retrieving the addresses of mail recipients.1 traditional use of the directory A directory-enabled application is an application that uses a naming or directory service. The query is called a search filter.4.4 combining naming and directory services Directories often arrange their objects in a hierarchy.50". many directories.
When using the JNDI as a Standard Extension on the JDK 1. you must have the JNDI classes and one or more service providers. Java applications can also use it as a repository for Java objects. The SPI enables a variety of naming and directory services to be plugged in transparently. It is also available as a Java Standard Extension for use with the JDK 1. For example. 13.naming. For example. 13. 13.3 includes three service providers for the following naming/directory services: • • • Lightweight Directory Access Protocol (LDAP) Common Object Request Broker Architecture (CORBA) Common Object Services (COS) name service Java Remote Method Invocation (RMI) Registry Other service providers can be downloaded from the JNDI Web site or obtained from other vendors.1 and Java 2 SDK. printer configuration and mail routing information can be stored in the directory so that it can be replicated and distributed for use by all printer-related and mailrelated applications and services.JNDI Applications can share the common infrastructure provided by the directory.3 and later releases.5 the JNDI API The Java Naming and Directory Interface TM (JNDI) is an application programming interface (API) that provides naming and directory functionality to applications written using the Java TM programming language. Thus a variety of directories--new. The Java 2 SDK. The JNDI is divided into five packages: • • • • javax.5.1 and the Java 2 SDK.event javax.13 .2.naming javax.1 and v1. This sharing makes applications that are deployed across the system. v1.2. It is defined to be independent of any specific directory service implementation. that is to store and retrieve Java objects.2 the directory as an object store In addition to using the directory in the traditional way.1 architecture The JNDI architecture consists of an API and a service provider interface (SPI). It extends the v1.directory javax.ldap 176 . v1. more coherent and manageable. 13. v1. a Java print client program should be able to look up a printer object from the directory and send a data stream to the printer object for printing.2 packaging The JNDI is included in the Java 2 SDK. and already deployed--can be accessed in a common way. thereby allowing the Java application using the JNDI API to access their services.2 platforms to provide naming and directory functionality. v1. you must first download the JNDI classes and one or more service providers. emerging. and even the network.5.naming.4.naming. Java applications use the JNDI API to access a variety of naming and directory services. To use the JNDI.
13.6 the naming package The javax. A java. A Name argument of any other type represents a compound name. the following code fragment looks up a printer and sends a document to the printer object to be printed. and it returns the object bound to that name. The most commonly used operation is lookup() . For example.lang. Java programs are but one group of applications that access them.String names are likely to be more useful for simple applications. 13. (Names are covered in the Beyond the Basics trail. some naming and directory services do not support the storing of Java objects. list() is useful for applications such as browsers that want to discover information about the objects bound within a context but that don't need all of the actual objects.6. Furthermore. which is the core interface for looking up. composing them. the name of the object's class.spi 13. renaming objects and creating and destroying subcontexts. Although listBindings() provides all of the same information. it is potentially a much more expensive operation. binding/unbinding. and the object itself. and so on. Name is an interface that represents a generic name--an ordered sequence of zero or more components.naming package contains classes and interfaces for accessing naming services.6. Each binding is represented by an instance of the Binding class.lookup("treekiller"). Printer printer = (Printer)ctx. a 177 .13 . 13.naming package defines a Context interface. NameClassPair contains an object's name and the name of the object's class. comparing components. The overloads that accept java. list() is similar to listBindings().6.6.4 references Objects are stored in naming and directory services in different ways. A service that supports storing Java objects might support storing an object in its serialized form.print(report).lang. for some objects in the directory.1 context The javax.2 names Every naming method in the Context interface has two overloads: one that accepts a Name argument and one that accepts a java. such as those that simply read in a name and look up the corresponding object. printer.3 bindings listBindings() returns an enumeration of name-to-object bindings. However. a Name argument that is an instance of CompositeName represents a composite name . A binding is a tuple containing the name of the bound object.String name argument represents a composite name. except that it returns an enumeration of NameClassPair. In this case.JNDI • javax.String name.) The overloads that accept Name are useful for applications that need to manipulate names. You supply lookup() the name of the object you want to look up.lang. that is. 13. For the methods in the Context interface. so you can name an object using a name that spans multiple namespaces.naming.
You can add.6 exceptions The JNDI defines a class hierarchy for exceptions that can be thrown in the course of performing naming and directory operations. The JNDI defines the Reference class to represent a reference. It defines methods for examining and updating attributes associated with a directory object. whereas its serialized form might contain a lot more state (see the Naming Concepts lesson). 13. The JNDI will attempt to turn references looked up from the directory into the Java objects that they represent so that JNDI clients have the illusion that what is stored in the directory are Java objects. all naming and directory operations are performed relative to a context. 178 . Programs interested in dealing with a particular exception can catch the corresponding subclass of the exception.13 . Attributes are modified using modifyAttributes(). You use getAttributes() to retrieve the attributes associated with a directory object (for which you supply the name). you can use it to look up other contexts and objects.naming package to provide functionality for accessing directory services in addition to naming services. which provides a starting point for naming and directory operations.2 searches DirContext contains methods for performing content-based searching of the directory.6. 13. they should catch NamingException. replace.naming. This package allows applications to retrieve attributes associated with objects stored in the directory and to search for objects using specified attributes. There are no absolute roots. This means that any directory object can also provide a naming context. A reference might be a very compact representation of an object.JNDI serialized Java object might not be the most appropriate representation. such as the person's printers and file system relative to that person directory object. 13. InitialContext. A reference contains information on how to construct a copy of the object. or remove attributes and/or attribute values using this operation.1 the directory context The DirContext interface represents a directory context.directory package extends the javax. For example.7 directory package The javax. a directory object for a person might contain attributes about that person as well as provide a context for naming objects.7. Once you have an initial context. the application specifies a set of attributes--possibly with specific values--to match and submits this attribute set to the search() method.7. The root of this class hierarchy is NamingException. Otherwise. 13. DirContext also behaves as a naming context by extending the Context interface. In the simplest and most common form of usage.5 the Initial context In the JNDI. Therefore the JNDI defines an initial context.6. Other overloaded forms of search() support more sophisticated search filters. 13.
2 controls The LDAP v3 allows any request or response to be augmented by yet-to-be defined modifiers.naming.directory package.1 "extended" operation In addition to specifying well-defined operations such as search and modify.JNDI 13. For example.naming. This package defines classes for the Start TLS extension. and vice versa. In fact. controls. To receive event notifications. Each category of event type has a corresponding type of NamingListener." and those that do not.ldap package at all.3 unsolicited notifications In addition to the normal request/response style of interaction between the client and server. The event contains a type that identifies the type of event. called controls .9 LDAP package The javax. 13. a NamespaceChangeListener represents a listener interested in namespace change events and an ObjectChangeListener represents a listener interested in object change events. A control may be defined by a standards organization such as the IETF or by a vendor. 13. event types are categorized into those that affect the namespace. the LDAP v3 (RFC 2251) specifies a way to transmit yet-to-be defined operations between the LDAP client and the server. Listeners A NamingListener is an object that listens for NamingEvents. or unsolicited notifications.event package contains classes and interfaces for supporting event notification in naming and directory services.directory package sufficient and will not need to use the javax. 13. Once registered. the listener will receive event notifications when the corresponding changes occur in the naming/directory service." A NamingEvent also contains other information about the change.13 . Events A NamingEvent represents an event that is generated by a naming/directory service. such as information about the object before and after the change. These operations are called "extended" operations. For example. A control sent with a request is a request control and a control sent with a response is a response control . that is. the LDAP v3 also specifies unsolicited notifications--messages that are sent from the server to the 179 . there need not be a response control for each request control sent. such as "object added. An "extended" operation may be defined by a standards organization such as the Internet Engineering Task Force (IETF) or by a vendor.8 event package The javax.naming.9. This package is primarily for those applications that need to use "extended" operations.9.naming. such as "object changed.naming.9. Event notification is described in detail in the Beyond the Basics trail. a listener must be registered with either an EventContext or an EventDirContext. Request controls and response controls are not necessarily paired. most JNDI applications that use the LDAP will find the javax.ldap package contains classes and interfaces for using features that are specific to the LDAP v3 that are not already covered by the more generic javax. 13.
180 . 13.naming package. 13.spi package supports implementors of Context. 13. This package also provides support for doing the reverse. The following code imports each class that is used from the javax.spi package provides the means by which developers of different naming/directory service providers can develop and hook up their implementations so that the corresponding services are accessible from applications that use the JNDI. This support is provided in the form of state factories.bind() and related methods can accept Java objects and store the objects in a format acceptable to the underlying naming/directory service.10.11 naming example This example shows you how to write a program that looks up an object whose name is passed in as a command-line argument.10 service provider package The javax. if you look up a printer name from the directory. That is. Therefore the name that you supply to the program must be a filename. This package provides support for different providers to cooperate to complete JNDI operations. 13. one service provider might need to interact with another service provider.10. sending request controls. 13.1 importing the JNDI classes Using your favorite text editor.naming.spi package allows different implementations to be plugged in dynamically. Examples of how to use these features are described in the Controls and Extensions lesson. These implementations include those for the initial context and for contexts that can be reached from the initial context.3 multiple naming systems (federation) JNDI operations allow applications to supply names that span multiple naming systems. In the process of completing an operation. import javax.1 plug-In architecture The javax.naming.13 .2 java object support The javax. for example to pass on the operation to be continued in the next naming system. create a file named Lookup.10.naming.4 the LDAP context The LdapContext interface represents a context for performing "extended" operations.JNDI client asynchronously and not in response to any client request. and receiving response controls.Context. 13. You do not need to understand details about the service provider at this point. then you likely would expect to get back a printer object on which to operate.lookup() and related methods to return Java objects that are natural and intuitive for the Java programmer. implementors of Context.11. 13. This support is provided in the form of object factories. You can import either the entire package or only individual classes and interfaces.java.9.naming. For example. It uses a service provider for the file system.
13. Context ctx = new InitialContext(env).naming. Otherwise. use Context.11.java).fscontext.jar that you downloaded from the JNDI Web site or by installing jndi.lookup(name).jar as an installed extension. you compile the source file using the Java compiler. 13. See the Preparations lesson for details on how to install the JNDI classes and service providers. as follows.sun. 181 .out.INITIAL_CONTEXT_FACTORY.println(name + " is bound to: " + obj). you can include the classes either by setting the CLASSPATH variable to include the jndi.4 catching NamingException The creation of the initial context and the lookup() method can throw a NamingException. } catch (NamingException e) { System. If you are still having problems.class in the same directory (folder) as the Java source file (Lookup. create an initial context. If the compilation fails. try { // Create the initial context Context ctx = new InitialContext(env). then the compiler will create a file named Lookup.err. using the capitalization shown. "com.lookup(name). If you are using the Java 2 SDK. For this reason. then see the Common Problems lesson for help.3. then make sure that you typed in and named the program exactly as shown here. 13.lookup() to look up an object. If the compilation succeeds. // Print it System.NamingException. env. } 13.naming.2 creating an initial context In the main() method of the program. import javax.InitialContext.put(Context. The following code looks up the object bound to the name supplied in the command line.JNDI import javax. Indicate that you're using the file system service provider by setting the environment properties parameter (represented by a Hashtable class) to the InitialContext constructor.11. How to set up the parameters for this constructor is explained in more detail in The Basics trail.13 . // Look up an object Object obj = ctx.5 compiling the program Next. you must have access to the JNDI classes. then the JNDI classes are already included. you need to enclose these calls inside a try/catch clause. Hashtable env = new Hashtable().RefFSContextFactory").11.jndi. v1.11.3 looking up an Object Next.println("Problem looking up " + name + ":" + e). Object obj = ctx. To compile to program. Here's the code fragment repeated with the try/catch clause.
13. The following code imports each class that is used from the javax. It uses an LDAP service provider to access an LDAP service.12.put(Context.InitialDirContext. To include the file system service provider classes (fscontext.jar).Attributes.jar and providerutil. javax. You can import either the entire package or only individual classes and interfaces.jndi.put(Context. To run the program.directory.13 . you need access to the JNDI classes. 13. 182 .naming.naming and javax. either include them in your CLASSPATH variable or install them as extensions. then you will see something like this: /tmp/f is bound to: //tmp/f 13. env. except that you use the constructor for InitialDirContext. "ldap://localhost:389/o=JNDITutorial"). env.RefFSContext@1dae083f If the name that you supplied is a file. javax.naming. import import import import import javax.2 creating an initial directory context In the main() method of the program. javax. supply the name of a file in your file system.NamingException. and your example class (Lookup. javax.12 directory example This example shows you how to write a program that retrieves attributes from a directory object.DirContext.naming.6 running the program To run the program. v1.fscontext.directory.3. Finally.naming.11. # java Lookup /tmp /tmp is bound to: com.INITIAL_CONTEXT_FACTORY.Context. the file system service provider. then you will see something like the following.LdapCtxFactory").sun.jndi.ldap.sun.class file in your the CLASSPATH variable. create an initial directory context. See the Preparations lesson for details on how to install the JNDI classes and service providers.naming.directory.naming.12. "com. Note that these archive files are not included with the Java 2 SDK. See the compilation step for instructions on including access to the JNDI classes.directory packages. Hashtable env = new Hashtable(). include the directory that contains your Lookup.1 importing the JNDI directory classes Using your favorite text editor.bat If you supply a file directory. as follows: # java Lookup /tmp Or as follows: # java Lookup \autoexec.java. This is similar to creating an initial context in the previous naming example.PROVIDER_URL. create a file named Getattr.JNDI 13.class).
out.println("sn: " + attrs.12.get() and then from that attribute get its value. then see the Common Problems lesson for help. Attributes.get("sn"). you indicate that you're using the LDAP service provider by setting the Hashtable parameter to the InitialDirContext constructor appropriately.4 extracting the desired attribute From a set of attributes. try { // Create the initial directory context DirContext ctx = new InitialDirContext(env). 13. compile the source file using the Java compiler.getAttributes("cn=Ted Geisel.java).err. If your LDAP server is located on another machine or is using another port. For now. Instructions for setting up a sample LDAP server for this tutorial are given in the Preparations lesson.getAttributes("cn=Ted Geisel. Details on how to set up the parameters for this constructor are given in The Basics trail. 13. 13.get().class in the same directory (folder) as the Java source file (Getattr. then you need to edit the LDAP URL ("ldap://localhost:389/o=JNDITutorial") accordingly. As with the naming example. If the compilation succeeds. If the compilation fails.12. then the compiler creates a file named Getattr. to do this you need access to the JNDI classes. use getAttributes() to get an object's attributes.12.3 getting a directory Object's attributes Next. using the capitalization shown. Similar to the naming example. // Ask for all attributes of the object Attributes attrs = ctx. Here's the code fragment repeated with the try/catch clause. } catch (NamingException e) { System. The following line first gets the surname attribute "sn" and then invokes Attribute.6 compiling the program Next. ou=People": Attributes attrs = ctx.JNDI DirContext ctx = new InitialDirContext(env).get("sn"). If you are still having problems. then make sure that you typed in and named the program exactly as shown here. For this reason. The following code retrieves all of the attributes associated with the object bound to the name "cn=Ted Geisel. you can ask for a particular attribute by using Attributes.12. ou=People"). 183 .get() on it to get its value: attrs. // Find the surname attribute ("sn") and print it System.println("Problem getting attribute:" + e). the only thing to understand is that the program by default identifies an LDAP server on the local machine.5 catching NamingException The method calls shown so far can throw a NamingException. you need to wrap these calls inside a try/catch clause.get()). } 13. ou=People").13 .
If you are using the Java 2 SDK. Getattr. Once it has the attributes.13 .PROVIDER_URL. this command queries the LDAP server on machine localhost that is listening on port 389.jar). ou=People". you need access to both the JNDI classes and your example class. You also need access to the LDAP service provider classes (ldap.7 running the program As with the naming example.class. # java Getattr sn: Geisel Recall that the program was configured with the following property. it extracts the surname attribute ("sn"). env. then see the Common Problems lesson.JNDI 13.) It asks for the attributes of the entry "cn=Ted Geisel. then these classes are already included. 184 . If you have any trouble running this example.jar and providerutil.12. v1. (See the Preparations lesson for details on this configuration step.put(Context.3. Here's an example of a command line for running Getattr and the output it generates. serving the "o=JNDITutorial" namespace. With this configuration. "ldap://localhost:389/o=JNDITutorial").
JMS is a part of the Java Platform. the messages are delivered in the order sent. JMS topic . unless it has established a durable 185 . neither the publisher nor the subscriber know about each other. Here.JAVA MESSAGE SERVICE 14 .2 JMS models The JMS API supports two models: • • point-to-point or queuing model publish and subscribe model In the point-to-point or queuing model. A message is removed from the queue once it has been read. and is defined by a specification developed under the Java Community Process as JSR 914.a distribution mechanism for publishing messages that are delivered to multiple subscribers. JMS queue . JMS message . The subscriber has to remain continuously active to receive messages.a JMS client that receives messages. It is characterized by following: • • • Only one consumer will get the message The producer does not have to be running at the time the consumer consumes the message.14 . a producer posts messages to a particular queue and a consumer reads messages from the queue.an application or process that produces and/or consumes messages. As the name queue suggests. the producer knows the destination of the message and posts the message directly to the consumer's queue. nor does the consumer need to be running at the time the message is sent Every message successfully processed is acknowledged by the consumer The publish/subscribe model supports publishing messages to a particular message topic. Providers are implemented as either a Java JMS implementation or an adapter to a non-Java MOM.1 JMS elements The Java Message Service (JMS) API is a Java Message Oriented Middleware (MOM) API for sending messages between two or more clients. The publisher has to create a subscription in order for clients to be able to subscribe. Enterprise Edition. • 14. JMS producer . Zero or more subscribers may register interest in receiving messages on a particular message topic.a JMS client that creates and sends messages. The following are characteristics of this model: • • Multiple consumers can get the message There is a timing dependency between publishers and subscribers.JAVA MESSAGE SERVICE 14.an object that contains the data being transferred between JMS clients.a staging area that contains messages that have been sent and are waiting to be read. JMS consumer . A good metaphor for it is anonymous bulletin board. In this model.An implementation of the JMS interface for a Message Oriented Middleware (MOM). JMS client . The following are JMS elements: • • • • • • JMS provider .
3 the JMS API programming model 14. The classes first use a connection factory to connect to the queue or topic.1 the ConnectionFactory interface An administered object that a client uses to create a connection to the JMS provider. On the receiving side. Using Java.14 .4.jms. The same Java classes can be used to communicate with different JMS providers by using the JNDI information for the desired provider. the clients then receive or subscribe to the messages. 14. JMS provides a way of separating the application from the transport layer of providing data.4 the JMS API The JMS API is provided in the Java package javax. messages published while the subscriber is not connected will be redistributed whenever it reconnects. Depending on the type of message. In that case.JAVA MESSAGE SERVICE subscription. 14. JMS clients access the connection factory through portable interfaces so the code does not need to be changed if the underlying implementation changes. users will use either a queue connection factory or topic connection factory. and then use populate and send or publish the messages. Administrators configure the connection factory in the Java Naming and Directory Interface (JNDI) namespace so that JMS clients can look them up. 186 .
lookup("jms/MyQueue"). It receives messages sent to a destination. A connection represents a communication link between the application and the messaging server. Before an application completes. The JMS administrator creates these objects. Like the connection factory.4.4. JMS administered objects are normally placed in the jms naming subcontext.4. ConnectionFactory connectionFactory = (ConnectionFactory) ctx. In a J2EE application. 14.close().JAVA MESSAGE SERVICE At the beginning of a JMS client program. connections allow users to create sessions for sending and receiving messages from a queue or topic.4 the MessageConsumer interface An object created by a session. connection. The following line of code looks up a queue named jms/MyQueue and casts and assigns it to a Queue object: Queue myQueue = (Queue) ctx.14 .lookup("jms/ConnectionFactory"). then cast and assign it to a ConnectionFactory object. For example. For example. It is either a queue or a topic. 14. If you want to stop message delivery temporarily without closing the connection. you must close any connections that you have created. Then it assigns it to a ConnectionFactory object: Context ctx = new InitialContext(). you must call the connection's start() method. you call the stop() method.3 the Destination interface An administered object that encapsulates the identity of a message destination.createConnection(). and users discover them using JNDI.lookup("jms/MyTopic"). you usually perform a JNDI lookup of a connection factory. The consumer can receive messages synchronously (blocking) or asynchronously (non-blocking) for both queue and 187 . the following line of code performs a JNDI lookup of the previously created topic jms/MyTopic and casts and assigns it to a Destination object: Destination myDest = (Destination) ctx. When you have a ConnectionFactory object. a connection to a JMS provider can be created.2 the Connection interface Once a connection factory is obtained. the following code fragment obtains an InitialContext object and uses it to look up a ConnectionFactory by name. Depending on the connection type. Closing a connection also closes its sessions and their message producers and message consumers. Before your application can consume messages. Connections implement the Connection interface. Failure to close a connection can cause resources not to be released by the JMS provider. the administrator can create two types of destinations: queues for Point-to-Point and topics for Publish/Subscribe. which is where messages are delivered and consumed. 14. you can use it to create a Connection: Connection connection = connectionFactory.
For example.receive(1000). Moreover. consumer. The onMessage() method takes one argument of type Message.) When message delivery begins.receive(). 14. it becomes active. onMessage(). Message delivery does not begin until you start the connection you created by calling its start() method. if you define a class named Listener that implements the MessageListener interface. MessageConsumer consumer = session.4. A message listener does.start(). you define the actions to be taken when a message arrives. // time out after a second To consume a message asynchronously.setMessageListener(myListener). you call the start() method on the Connection to begin message delivery. you are likely to miss messages. usually expect a specific message type and format. depending on the type of destination for which the message consumer was created. 188 . forgetting to start the connection is one of the most common JMS programming errors.JAVA MESSAGE SERVICE topic-type messaging.createConsumer(myQueue). and you can use it to receive messages.14 . You use the Session. connection. (If you call start() before you register the message listener.createConsumer(myTopic).5 the MessageListener interface A message listener is an object that acts as an asynchronous event handler for messages. For example. This object implements the MessageListener interface. you use a Session to create a MessageConsumer for either a queue or a topic: MessageConsumer consumer = session. This method is valid only if you are using a topic.start(). the JMS provider automatically calls the message listener's onMessage() method whenever a message is delivered. Message m = consumer. You can use the close() method for a MessageConsumer to make the message consumer inactive. a message listener object may be used. After you register the message listener. (Remember always to call the start() method.createDurableSubscriber() method to create a durable topic subscriber. a message listener must either assume a particular destination type or obtain the destination type of the message and create a producer for that destination type. which your implementation of the method can cast to any of the other message types. After you have created a message consumer. A message listener is not specific to a particular destination type. you can register the message listener as follows: Listener myListener = new Listener(). The same listener can obtain messages from either a queue or a topic. You can use this method at any time after you call the start method: connection. if it needs to reply to messages. You register the message listener with a specific MessageConsumer by using the setMessageListener() method. however. In the onMessage() method.) You use the receive method to consume a message synchronously. Message m = consumer. which contains one method.
a message arrives as a generic Message object and must be cast to the appropriate message type.createProducer(myQueue). 14. With an unidentified producer. 189 . A message has three main parts: 1.JAVA MESSAGE SERVICE 14. if you created an unidentified producer. A message body (optional): Allows users to create five types of messages (text message.send(message). 3. MessageProducer producer = session.6 the MessageProducer interface An object created by a session that sends messages to a destination.send(myQueue. Here. The JMS API provides methods for creating messages of each type and for filling in their contents. The following code fragment uses the getText method: Message m = consumer. to create and send a TextMessage.4. At the consuming end.receive(). that is. For example. It can be used to create custom fields or filters (selectors).7 the Message interface An object that is sent between consumers and producers. the first example creates a producer for the destination myQueue. The user can create a sender to a specific destination or create a generic sender that specifies the destination at the time the message is sent. and the second for the destination myTopic: MessageProducer producer = session. You can create an unidentified producer by specifying null as the argument to createProducer. You use a Session to create a MessageProducer for a destination. and object message). use an overloaded send method that specifies the destination as the first parameter. message). The message interface is extremely flexible and provides numerous ways to customize the contents of a message.createProducer(null). bytes message. You must first create the messages. For example: MessageProducer anon_prod = session. if (m instanceof TextMessage) { TextMessage message = (TextMessage) m.send(message). message.14 .4. map message.setText(msg_text). You can use one or more getter methods to extract the message contents. you can use it to send messages by using the send method: producer. stream message.createTextMessage(). A set of message properties (optional): Contains additional properties to support compatibility with other providers or users. anon_prod. A message header (required): Contains operational settings to identify and route messages 2. you might use the following statements: TextMessage message = session. you do not specify a destination until you send a message. // msg_text is a String producer. from one application to another.createProducer(myTopic). After you have created a message producer.
To create a transacted session. The benefit of a session is that it supports transactions. 190 . meaning that messages are received one-by-one in the order sent. A session allows users to create message producers to send messages. you use it to create a Session: Session session = connection. Session. Before committing the transaction.out. the second means that the session automatically acknowledges messages when they have been received successfully. If the user selects transaction support. } else { // Handle error } 14.AUTO_ACKNOWLEDGE).8 the Session interface Represents a single-threaded context for sending and receiving messages. The first argument means that the session is not transacted.JAVA MESSAGE SERVICE System.14 . the user can cancel the messages using a rollback operation.println("Reading message: " + message. and message consumers to receive messages. Here. 0).getText()). the first argument means that the session is transacted. After you create a Connection object. the session context holds a group of messages until the transaction is committed. the second indicates that message acknowledgment is not specified for transacted sessions.createSession(false.4. Sessions implement the Session interface. then delivers the messages. use the following code: Session session = connection.createSession(true. A session is singlethreaded so that messages are serialized.
The EJBs will run in an EJB container which is part of an application server. Version 1. 15.no developer coding. bundled into a single unit. while the EJB (Enterprise Java Beans) architecture provides a format for highly specialized business logic components.1 of EJB specification provides two EJB types: • • session beans . component recovery scalability portability 191 . The component lives inside a container.DB interaction transactions .logging. the container lives (in general) in an application server. container which offers services to the component. On the other side. so no XML descriptor is needed and beans deployment can be done just through a plain . It provides annotations for every type of metadata previously addressed by deployment descriptors.object oriented representation of data in a DB.consistent error handling framework . message-driven beans The 2.jar file into the application server.intended to be used by a single client (client extension on the server). The main reason for using EJBs is to take advantage of the services provided by the container.transaction management can be complex.2 the ejb container and its services The EJB container provides an execution environment for a component. multiple clients can access it simultaneously while its life-span is the same as the data it represents.EJB access can be stated without extra coding error handling . The Java classes must follow certain rules and must offer certain callback methods. bean's life span can be no longer than client's entity beans .ENTERPRISE JAVA BEANS 15 . Novelties in this specification try to make the development of EJBs easier.15 .ENTERPRISE JAVA BEANS 15. What are Enterprise Java Beans? A collection of Java classes together with an xml file.0 EJB specification adds another bean type: • The current EJB specification is 3.0. These services are: • • • • • • • persistence .0. improved performance security . Entity beans have been superseded by the Java Persistence API in EJB 3. server which provides an execution environment for containers. especially if we have more databases and more access components data caching .1 enterprise java beans versus (ordinary) java beans (Ordinary) Java beans provide a format for general-purpose components.
the remote interface of the bean 4. which is an xml file. Handle – abstraction for a network reference to an EJB. The methods specified by the EJBHome interface (not implemented (in general) by the programmer) are the following: public void remove(Handle han) throws RemoteException. the bean itself (the class that contains the business logic ) 2. called ejb-jar. RemoveException public EJBMetaData getEJBMetaData() throws RemoteException public HomeHandle getHomeHandle() throws RemoteException 192 . It provides methods named create() with application specific arguments.15 . the deployment descriptor. returning the remote interface and throwing CreateException and RemoteException. the home interface of the bean 3.ENTERPRISE JAVA BEANS • manageability 15. It is bean's programmer task to create them (at least). It uses only argument types allowed by the RMI standard.3 enterprise java beans architecture An EJB consists of (at least) 3 classes and an xml file.4 the home interface The home interface of an ejb is an interface that extends the EJBHome interface.xml 15. as follows: 1. RemoveException public void remove(Object primaryKey) throws RemoteException.
RemoteException. int custId) throws RemoteException. String lastName. The developer does not implement this interface. void deleteEntry(int custId) throws RemoteException.*.15 . RemoteException. import.ENTERPRISE JAVA BEANS Code example for the a home interface. import.ejb. RemoveException Code example for a remote interface called MyBeanObject: package myBeans.ejb.*. import java. public interface MyBeanHome extends EJBHome { MyBeanObject create() throws CreateException. the EJBObject declares the following ones: public EJBHome getEJBHome() throws RemoteException public Object getPrimaryKey() throws RemoteException public Handle getHandle() throws RemoteException public boolean isIdentical(EJBObject obj) throws RemoteException public void remove() throws RemoteException. } 193 .rmi.RemoteException. import java.5 the remote interface The remote interface of a bean is a standard Java interface that extends the EJBObject and Remote interfaces and declares the business logic methods of the bean. While the Remote interface declares no methods.javax. public interface MyBeanObject extends EJBObject { // assume that we have two business logic methods void processEntry(String firstName.rmi. called MyBeanHome: package myBeans. } 15.javax.
getting the InitialContext requires the usage of some server-side properties.jnp. prop. implemented by an object built by the EJB host in the deployment process. how to create or find the bean 2. we need to know: 1.6 client programmer's viewpoint For an EJB client application. Here is an example: • try { Properties prop = new Properties(). "localhost:1099"). The client gains access to the EJB through a remote interface. creating them for the client application.NamingContextFactory". This object acts like a factory for EJBs. what methods to use (know its interface) 3. Here are the main parts of the client code: authentication Client's authentication is done in a way which is server specific. getting an initial context if the client is another EJB executing in the same container and the bean to be used is declared as a resource in the deployment descriptor.interfaces. how to release its resources The client is able to create an EJB through an object implementing the EJBHome interface. In the case of an web application.put(Context.15 . "org.INITIAL_CONTEXT_FACTORY.put(Context. Context ctx = new InitialContext(prop).ENTERPRISE JAVA BEANS 15. this can be done (for example) through SSL. the InitialContext is already available: • Context ctx = new InitialContext().PROVIDER_URL. } 194 . prop. if the client executes outside the container.
in fact. to the appropriate type. The underlying protocol that it is used for the communication is IIOP (Internet Inter ORB Protocol). Why do we have to use the narrow() method? Usually. create an instance of the bean The instance of the bean is created on the server. the client should use the narrow() method of javax. in fact. the bean can be associated to any name in the JNDI name space. the code may look like: • Object homeRef = ctx. that is part of CORBA standards. It is normally used to describe this communication system using the Java RMI over IIOP. Java RMI-IIOP provides a mechanism to narrow the the Object you have received from your lookup.PortableRemoteObject class and. It is JNDI's task to identify the resource associated to the name provided: Object homeRef = ctx.narrow(homeRef.class). MyBeanHome..Remote interface).rmi. but for generic languages. Some languages. Problem is. The client only has a remote interface to this instance (i. 195 . when we perform a lookup() on a Context object. cast the home interface reference To make sure that the client works with the underlying communication protocol. using the narrow() method.15 . • if the client executes outside the container. the method will return you an Object that needs to be casted to the home interface we've asked for. the communication between the server and the client is based on RMI (both remote and local interfaces. IIOP has not been designed for Java. and this means that there are some limitations. This is done through the javax. Why? For EJB.ENTERPRISE JAVA BEANS find the home interface of the bean for a client executing inside the container. do not have the concept of casting. this cannot be done using the normal/explicit casting: MyBeanHome myHome = (MyBeanHome)returnedObject The reason has to do with CORBA.e. the client has a stub). do implements the java.lookup("java:comp/env/ejb/MyBean").rmi.lookup("MyBean").PortableRemoteObject: MyBeanHome myHome = (MyBeanHome)PortableRemoteObject. more specifically.rmi.
} public void deleteEntry(int custId) { // method implementation . call business methods on the bean myObject.. } // mandatory methods for session beans // method implementations may be empty public void ejbCreate() {} public void ejbRemove() {} public void ejbActivate() {} 196 .SessionBean { public void processEntry(String firstName. Assuming that our bean (called MyBean) is a session bean.SessionContext. set which is specific to each major type of beans (session or entity). "Vasile".7 bean programmer's viewpoint Since the home interface and the remote interface have been detailed in the previous sections. remove the bean instance myObject..create(). 1102).15 .. we concentrate now on the bean class itself. Besides the implementation of the business methods (which were declared in the remote interface.bank11.ccards. as well).ejb.ejbeans.ejb.remove(). public class MyBean implements javax.processEntry("Dumitrascu". String lastName. the bean class must implement (although the implementation itself may be empty) a certain set of methods. int custId) { // method implementation . the code implementing this class may look like this: package com.. 15.ENTERPRISE JAVA BEANS Here is the code: MyBeanObject myObject = myHome. import javax.
because the container will never activate a stateless session bean.10 the life cycle of a stateful session bean Figure 15. When an EJB server needs to conserve its resources. 15. To passivate the bean and preserve its conversational state. The bean is now ready to have its business methods invoked. When a client invokes a method on the EJB object. 197 . the object is activated.1 illustrates the stages that a session bean passes through during its lifetime. A stateless bean does not. a new stateful instance is instantiated and populated from the passivated storage. The client initiates the life cycle by invoking the create method. that is. it can evict stateful session beans from memory.ENTERPRISE JAVA BEANS public void ejbPassivate() {} public void setSessionContext(SessionContext ctx) {} } The deployment descriptor of the bean will be detailed in another section. A stateful session bean preserves data between client accesses. the bean's state is serialized to a secondary storage. 15. namely stateful and stateless beans.9 container callbacks for session beans There are 5 mandatory callbacks for classes implementing the SessionBean interface.8 session beans There are two types of session beans. public void ejbActivate() public void ejbPassivate() public void ejbCreate() public void ejbRemove() public void setSessionContext(SessionContext ctx) The first two methods will never be called for stateless session beans.15 . 15. This reduces the number of instances maintained by the server. The EJB container instantiates the bean and then invokes the setSessionContext and ejbCreate methods in the session bean.
198 . The ejbCreate method. you might wish to connect to a database in the ejbCreate method. and then moves it to the ready stage. for example.1 are invoked by the EJB container. If a client invokes a business method on the bean while it is in the passive stage. For example. calls the bean's ejbActivate method. the client invokes the remove method. All other methods in Figure 15. and the EJB container calls the bean's ejbRemove method. is inside the bean class.1 Life Cycle of a Stateful Session Bean While in the ready stage. Your code controls the invocation of only two life-cycle methods: the create and remove methods in the client.11 the life cycle of a stateless session bean Because a stateless session bean is never passivated. At the end of the life cycle.2 illustrates the stages of a stateless session bean. The bean's instance is ready for garbage collection.) The EJB container invokes the bean's ejbPassivate method immediately before passivating it. the EJB container may decide to deactivate. the EJB container activates the bean.ENTERPRISE JAVA BEANS Figure 15. Figure 15.15 . (Typically. its life cycle has only two stages: nonexistent and ready for the invocation of business methods. allowing you to perform certain operations right after the bean is instantiated. the EJB container uses a least-recentlyused algorithm to select a bean for passivation. 15. or passivate. the bean by moving it from memory to secondary storage.
ENTERPRISE JAVA BEANS Figure 15. maintaining a cache between transactions 4. The EJB container provides the developer several persistence services: 1. stored in a Database). support for concurrent access 3.13 primary keys Every entity bean has a primary key. This primary key must be represented by a primary key class.15 . providing all the persistence management code (no SQL code necessary) There are 2 main types of entity beans. The requirements that must be satisfied by the primary key are different for the two main types of entity beans.12 entity beans Entity beans represent actual data (usually.2 Life Cycle of a Stateless Session Bean 15. • • CMPs (Container Managed Persistence) BMPs (Bean Managed Persistence) for which the bean developer provides the actual persistence (SQL) code 15. For BMPs: • • the primary key can be any legal RMI/IIOP type it must provide suitable implementations for hashCode(). container callbacks to manage caching within a transaction 2. equals() 199 .
14.ccards. namely ejbCreate() and ejbPostCreate().ENTERPRISE JAVA BEANS • must have a unique value among beans of a particular type For CMPs: • • the container must be able to create a primary key the key class must have a no argument constructor The fully qualified name of the primary key is always specified in the deployment descriptor (except when it is not known until deployment) An example: <prim-key-class>com. an entity bean must implement (although this implementation may be left empty) the following methods: public void ejbActivate() public void ejbPassivate() public void setEntityContext(EntityContext ctx) public void unsetEntityContext() CRUD translates through Create.14 mandatory callbacks for entity beans Besides the CRUD callbacks which are discusses later in this section. as the parameters in the original create() method. in the same order. 15. Read. state data is stored into data store (usually.bank11.lang.1 create When a client calls a create() method on a session bean's home interface. the field is specified: <prim-key-field>sportsTeamID</prim-key-field> 15. when a client calls create() on an entity bean's home interface. This is transactional data that is accessible to multiple clients. On the other side. an instance of that bean is created. CreateException. Update and Delete.CustomerID</prim-key-class> or <prim-key-class>java. 200 .String</prim-key-class> In the case of CMP using a simple type as primary key. all throwing RemoteException. methods which have the same parameters.15 . a Database) (we actually insert a record in a database). We can have more create() methods. These methods are mandatory for entity beans. Each create() method from the Home interface of the bean has 2 correspondent methods in the bean implementation class.
the entity bean moves to a pool of available instances. the EJB container can invoke the ejbPassivate method.14. 15. the method can be used for preprocessing data to be stored. After the EJB container creates the instance.3 shows the stages that an entity bean passes through during its lifetime. causing the EJB container to call the ejbCreate and ejbPostCreate methods. After instantiation.4 delete • • the corresponding method in the bean implementation class is ejbRemove() data is deleted from DB (in the CMP case). in BMP. the EJB container invokes the ejbActivate method. The setEntityContext method passes the entity context to the bean. the instance is not associated with any particular EJB object identity. a client can invoke the remove method. which causes the EJB container to call the ejbRemove method. All instances in the pool are identical. for BMP. There are also two paths from the ready stage to the pooled stage. While an entity bean is in the ready stage. but the developer returns null for CMP. for BMPs. but in general. On the first path. There are two paths from the pooled stage to the ready stage. On the second path. ejbCreate() must have insertion SQL code and returns an instance of the primary key.ENTERPRISE JAVA BEANS • • the return type of the ejbCreate() is the same as the primary key. but needs actual SQL code in BMP the bean's persistence implementation may choose to defer loading until it is used ejbLoad() may contain processing code 15. the client invokes the create method. First. the programmer will create actual SQL code.15 the life cycle of an entity bean Figure 15. not null. it's business methods can be invoked.14. left empty most of the time in CMP. actual SQL update code. The EJB container assigns an identity to an instance when moving it to the ready stage.14. Second.15 . While in the pooled stage. it is empty. 201 . the updated data is to be stored immediately 15.3 update • • ejbStore() in CMP. 15.2 read • • • ejbLoad(). it calls the setEntityContext method of the entity bean class.
when the EJB container moves an instance from the pooled state to the ready state. Therefore.15 .16 message-driven beans A message-driven bean is an enterprise bean that allows J2EE applications to process messages asynchronously. If the primary key is incorrect. With bean-managed persistence.ENTERPRISE JAVA BEANS Figure 15. The messages may be sent by any J2EE component . You can make these instance variables eligible for garbage collection by setting them to null in the ejbPassivate method. the EJB container removes the instance from the pool and invokes the unsetEntityContext method. In the pooled state.3 Life Cycle of an Entity Bean At the end of the life cycle. It acts as a JMS message listener. but in the future they may be used to process other kinds of messages. the ejbLoad and ejbStore methods cannot synchronize the instance variables with the database. The ejbActivate method sets the primary key (id) as follows: id = (String)context. In the pooled state. or a Web component .an application client. 202 . the ejbCreate and ejbActivate methods must assign a value to the primary key. 15. it does not automatically set the primary key. another enterprise bean.or by a JMS application or system that does not use J2EE technology. Message-driven beans currently process only JMS messages. which is similar to an event listener except that it receives messages instead of events.getPrimaryKey(). an instance is not associated with any particular EJB object identity. the values of the instance variables are not needed.
The onMessage method normally casts the message to one of the five JMS message types and handles it in accordance with the application's business logic. change the weblogic-ejb-jar. 203 . A message may be delivered to a message-driven bean within a transaction context. allowing the EJB container to assign a message to any message-driven bean instance.16.ENTERPRISE JAVA BEANS 15.16. or an object reference to an enterprise bean object. To ensure concurrency.for example. The onMessage method may call helper methods. 15.16. a JMS API connection. To avoid tying up server resources. by sending a message to a JMS Queue or Topic. 15. message-driven beans are different from stateless session EJBs (and other types of EJBs) in several significant ways: • • message-driven beans process multiple JMS messages asynchronously. the container calls the message-driven bean's onMessage method to process the message. max-beans-infree-pool. a message-driven bean has only a bean class. If this element is set to more than one. the message will be redelivered. Clients interact with message-driven beans only indirectly. but not asynchronously. a message-driven bean resembles a stateless session bean. Unlike a session or entity bean. message-driven bean can be used.15 . you may prefer not to use blocking synchronous receives in a server-side component. an open database connection. To receive messages in an asynchronous manner. The container can pool these instances to allow streams of messages to be processed concurrently. a single message-driven bean can process messages from multiple clients.4 concurrent support for message-driven beans Message-driven Beans support concurrent processing for both topics and queues. 15. When a message arrives. If message processing is rolled back. Previously. or it may invoke a session or entity bean to process the information in the message or to store it in a database. all instances of a message-driven bean are equivalent. the container will spawn as many threads as specified.2 differences between message-driven beans and the other ejb's The most visible difference between message-driven beans and session and entity beans is that clients do not access message-driven beans through interfaces.16. • • • a message-driven bean's instances retain no data or conversational state for a specific client. rather than processing a serialized sequence of method calls. so that all operations within the onMessage method are part of a single transaction.3 differences between message-driven beans and stateless session EJBs Although the dynamic creation and allocation of message-driven bean instances mimics the behavior of stateless session EJB instances. and therefore cannot be directly accessed by internal or external clients. For more information on this element see. The instance variables of the message-driven bean instance can contain some state across the handling of client messages .1 when to use message-driven beans Session beans and entity beans allow you to send JMS messages and to receive them synchronously. message-driven beans have no home or remote interface. only concurrent processing for Queues was supported.xml deployment descriptor maxbeans-in-free-pool setting to >1. In several respects.
} // onMessage() is required. // The EJB class cannot define a finalize() method } Creating and Removing Bean Instances The WebLogic Server container calls the message-driven bean's ejbCreate() and ejbRemove() methods when creating or removing an instance of the bean class. public void onMessage(javax.. Note: These instances can be pooled.}.5 invoking a message-driven bean When a JMS Queue or Topic receives a message..0 specification. 15. 3. the ejbCreate() method in the bean class should prepare any resources that are 204 .ENTERPRISE JAVA BEANS 15. finalize{}. // The throws clause (if used) must not include an application //exception.0 specification provides detailed guidelines for defining the methods in a messagedriven bean class. ejbRemove() must not be declared as final or static. and must take a single parameter of // type javax. 2. and it must not // accept parameters. Call the bean's onMessage() method to perform business logic. See Implementing Business Logic with onMessage().ejb. The following output shows the basic components of a message-driven bean class.7 bean class requirements The EJB 2. // An EJB constructor is required.jms.. As with other EJB types. 15.6 developing message-driven beans To create message-driven EJBs. call the bean's setMessageDrivenContext() to associate the instance with a container context.16. onMessage() must not be // declared as final or static. Classes. Obtain a new bean instance.16. See Creating and Removing Bean Instances. The bean can utilize elements of this context as described in Using the Message-Driven Bean Context. as well as observe several general practices that result in proper bean behavior. The throws clause (if used) must not // include an application exception..15 .} // ejbRemove() is required and must not accept parameters. The constructor must not be declared as // final or abstract. If the bean cannot be located in the pool and a new one must be created. or create a new one..Message MessageName) {. methods. you must follow certain conventions described in the JavaSoft EJB 2. and method declarations in bold are required as part of the EJB 2. use WebLogic Server to call an associated message-driven bean as follows: 1..jms. public void ejbRemove() {.0 specification: { public class MessageTraderBean implements javax. Obtain a new bean instance from the connection pool if one already exists.16.MessageDrivenBean public MessageTraderBean() {.Message.
jms.9 implementing business logic with onMessage() The message-driven bean's onMessage() method performs all of the business logic for the EJB. 15. Message-driven beans should also perform some form of regular clean-up routine outside of the ejbRemove() method. whose properties can be accessed from within the instance by using the following methods from the MessageDrivenContext interface: • • • • • getCallerPrincipal() isCallerInRole() setRollbackOnly(). 15. or by having the WebLogic Server container 205 .16. the client context is not passed along with the JMS message. Note: Although getEJBHome() is also inherited as part of the MessageDrivenContext interface. 15. if the EJB throws a runtime exception). from the client perspective the EJB still exists. even in onMessage(). Make sure that the business logic accounts for asynchronous message processing. it cannot be assumed that the EJB receives messages in the order they were sent by the client. so that they are freed before WebLogic Server removes the instance.15 . passing the full JMS message object as an argument. If any method throws such an exception.The EJB can use this method only if it utilizes containermanaged transaction demarcation. because the beans cannot rely on ejbRemove() being called under all circumstances (for example. although individual onMessage() calls to a given messagedriven bean instance are serialized. See javax.ENTERPRISE JAVA BEANS required for the bean's operation. It is the messagedriven EJB's responsibility to parse the message and perform the necessary business logic in onMessage(). getRollbackOnly() . Calling getEJBHome() from within a message-driven EJB instance yields an IllegalStateException.This is not a client context. WebLogic Server provides the EJB with a container context.The EJB can use this method only if it utilizes containermanaged transaction demarcation.16. However. getUserTransaction(). Instance pooling within the container means that messages are not received or processed in a sequential order.8 using the message-driven bean context WebLogic Server calls setMessageDrivenContext() to associate the message-driven bean instance with a container context. 15. message-driven EJBs do not have a home interface.10 handling exceptions Message-driven bean methods should not throw an application exception or a RemoteException. WebLogic Server immediately removes the EJB instance without calling ejbRemove(). message-driven beans can demarcate transaction boundaries either on their own (using bean-managed transactions). because future messages are forwarded to a new instance that WebLogic Server creates.16.11 transaction services for message-driven beans As with other EJB types. WebLogic Server calls onMessage() when the EJB's associated JMS Queue or Topic receives a message.The EJB can use this method only if it utilizes beanmanaged transaction demarcation.16. The ejbRemove() method should release those resources.onMessage() for more information.MessageListener. For example.
WebLogic Server includes the message receipt as part of the bean's transaction only if the bean's transaction attribute is set to Required. a message-driven bean does not receive a transaction context from the client that sends a message. as required by the EJB 2. WebLogic Server always calls a bean's onMessage() method by using the transaction context specified in the bean's deployment descriptor.16.13 message acknowledgment For message-driven beans that use container-managed transaction demarcation.ENTERPRISE JAVA BEANS manage transactions (container-managed transactions). Because no client provides a transaction context for calls to a message-driven bean. If the EJB uses bean-managed transactions.14 deployment elements The EJB 2. both the receipt and the acknowledgment of a message occur outside of the EJB transaction context.16. Transaction attributes are defined in ejb-jar.0 specification.12 message receipts The receipt of a JMS message that triggers a call to an EJB's onMessage() method is not generally included in the scope of a transaction. beans that use container-managed transactions must be deployed using the Required or NotSupported transaction attribute in ejb-jar.xml as follows: <assembly-descriptor> <container-transaction> <method> <ejb-name>MyMessageDrivenBeanQueueTx</ejb-name> <method-name>*</method-name> </method> <trans-attribute>NotSupported</trans-attribute> </container-transaction> </assembly-descriptor> 15. you edit the XML file to create the deployment descriptors that associate the EJB with a configured JMS destination. In either case. WebLogic Server automatically acknowledges a message when the EJB transaction commits.16.0 specification adds the following new XML deployment elements for deploying 206 . WebLogic Server automatically acknowledges messages for EJBs with bean-managed transactions. For EJBs that use bean-managed transactions.15 . Deploying Message-Driven Beans in WebLogic Server To deploy a message-driven bean on WebLogic Server. 15.xml. Deployment Descriptors The deployment descriptor for a message-driven bean also specifies: • • • • Whether the EJB is associated with a JMS Topic or Queue Whether an associated Topic is durable or non-durable Transaction attributes for the EJB JMS acknowledgment semantics to use for beans that demarcate their own transactions 15. For EJBs that use container-managed transaction demarcation. the message receipt is always outside the scope of the bean's transaction.0 specification. as described in the EJB 2. but the deployer can configure acknowledgment semantics using the jms-acknowledge-mode deployment parameter.
• • These elements are defined in the ejb-jar.4 illustrates the stages in the life cycle of a message-driven bean. The EJB container usually creates a pool of message-driven bean instances.17 the life cycle of a message-driven bean Figure 15.0 specification. </message-driven> . the weblogic-ejb-jar. This element has two possible values: AUTO_ACKNOWLEDGE (the default) or DUPS_OK_ACKNOWLEDGE. </enterprise-beans> In addition to the new ejb-jar. subscription-durability specifies whether or not an associated Topic should be durable.15 .xml elements.Topic </jms-destination-type> </message-driven-destination> . It calls the instance's ejbCreate method. 207 . 15... • message-driven-destination specifies whether the EJB should be associated with a JMS Queue or Topic destination. The following excerpt shows a sample XML stanza for defining a message-driven bean: <enterprise-beans> <message-driven> <ejb-name>exampleMessageDriven1</ejb-name> <ejb-class>examples.ejb20.xml file includes a new message-driven-descriptor stanza to associate the message-driven bean with an actual destination in WebLogic Server. For each instance..xml deployment file. It calls the setMessageDrivenContext method to pass the context object to the instance. as described in the EJB 2.jms..MessageTraderBean</ejb-class> <transaction-type>Container</transaction-type> <message-driven-destination> <jms-destination-type> javax.message. 2.ENTERPRISE JAVA BEANS message-driven beans. jms-acknowledge-mode specifies the JMS acknowledgment semantics to use for beans that demarcate their own transaction boundaries. the EJB container instantiates the bean and performs these tasks: 1.
which users can access a bean or a particular method of a bean 2. the home interface name 7. and it has only two states: nonexistent and ready to receive messages. the container calls the ejbRemove method.18 the deployment descriptor The deployment descriptor of an EJB contains information about the bean in relation to the application it belongs to. access control entries . the remote interface name 8. At the end of the life cycle. entity specific elements 10. application assembly information Although not an exhaustive one.15 . 15. EJB class name 5. control descriptors . isolation level. here is a typical list of entries (elements) in a deployment descriptor: 1. This information can be divided into two main categories: • • structural information related to a particular EJB.name under which the bean is registered under JNDI 3.4 Life Cycle of a Message-Driven Bean Like a stateless session bean. bean home name .security issues.like transaction.specifies control attributes for transactions 4. attributes . security 208 .ENTERPRISE JAVA BEANS Figure 15. environment properties 6. The bean's instance is then ready for garbage collection. session specific elements 9. a message-driven bean is never passivated.
here is how the deployment descriptor may look like: <?xnm version="1.1"?> <ejb-jar> <entrprise-beans> <session> <ejb-name>CCEnroll</ejb-name> <home>com.bank11.bank11.Integer</prim-key-class> <reentrant>False</reentrant> <cmp-field> <field-name>accountNumber</field-name> 209 .15 .ccards.ejb.bank11.ccards.CCEnrollHome</home> <remote>com.AccountObj</remote> </ejb-ref> <security-role-ref> <description> This role relates to cash advances from ATMs </description> <role-name>CashAdvATM</role-name> <security-role-ref> </session> <entity> <ejb-name>Account</ejb-name> <home>com.ccards.ENTERPRISE JAVA BEANS Keeping in mind that the application assembler is to follow.ccards.ccards.ccards.Accountbject</remote> <ejb-class>com.AccountHome</home> <remote>com.bank11.CCEnroll</ejb-class> <session-type>Stateless</session-type> <transaction-type>Container<transaction-type> <ejb-ref> <ejb-ref-name>ejb/CCAccount</ejb-ref-name> <ejb-ref-type>Entity</ejb-ref-type> <home>com.lang.ejb.Account</ejb-class> <persistence-type>Container</persistence-type> <prim-key-class>java.ccards.bank11.ejb.bank11.CCEnrollObject</remote> <ejb-class>com.AccountHome</home> <remote>com.ccards.bank11.ejb.bank11.
</enterprise-beans> <assembly-descriptor> <container-transaction> <method> <ejb-name>CCEnroll</ejb-name> <method-name>*</method-name> </method> <trans-attribute>Required</trans-attribute> </container-transaction> </assembly-descriptor> </ejb-jar> 210 .ENTERPRISE JAVA BEANS </cmp-field> <cmp-field> <field-name>userName</field-name> </cmp-field> <cmp-field> <field-name>customerID</field-name> </cmp-field> <cmp-field> <prim-key-field>accountNumber</prim-key-field> </cmp-field> <env-entry> <env-entry-name>env/minPaymentPerc</env-entry-name> <env-entry-type>java.15 .Float</env-entry-type> <env-entry-value>2.lang. Here is a very lean one: </ejb-jar> <enterprise-beans> ...5</env-entry-value> </env-entry> </entity> </enterprise-beans> </ejb-jar> The assembly descriptor combines EJBs into a deployable application.
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