Chapter 110. Freemarker Component
Chapter 110. Freemarker Component Available as of Camel version 2.10 The freemarker: component allows for processing a message using a FreeMarker template. This can be ideal when using Templating to generate responses for requests. Maven users will need to add the following dependency to their pom.xml for this component: <dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-freemarker</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency> 110.1. URI format freemarker:templateName[?options] Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (eg: file://folder/myfile.ftl ). You can append query options to the URI in the following format, ?option=value&option=value&... 110.2. Options The Freemarker component supports 4 options, which are listed below. Name Description Default Type allowContextMapAll (producer) Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so imposes a potential security risk as this opens access to the full power of CamelContext API. false boolean allowTemplateFromHeader (producer) Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. false boolean configuration (advanced) To use an existing freemarker.template.Configuration instance as the configuration. Configuration resolveProperty Placeholders (advanced) Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. true boolean The Freemarker endpoint is configured using URI syntax: with the following path and query parameters: 110.2.1. Path Parameters (1 parameters): Name Description Default Type resourceUri Required Path to the resource. You can prefix with: classpath, file, http, ref, or bean. classpath, file and http loads the resource using these protocols (classpath is default). ref will lookup the resource in the registry. bean will call a method on a bean to be used as the resource. For bean you can specify the method name after dot, eg bean:myBean.myMethod. String 110.2.2. Query Parameters (7 parameters): Name Description Default Type allowContextMapAll (producer) Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so imposes a potential security risk as this opens access to the full power of CamelContext API. false boolean allowTemplateFromHeader (producer) Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. false boolean configuration (producer) Sets the Freemarker configuration to use Configuration contentCache (producer) Sets whether to use resource content cache or not false boolean encoding (producer) Sets the encoding to be used for loading the template file. String templateUpdateDelay (producer) Number of seconds the loaded template resource will remain in the cache. int synchronous (advanced) Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). false boolean 110.3. Spring Boot Auto-Configuration The component supports 3 options, which are listed below. Name Description Default Type camel.component.freemarker.configuration To use an existing freemarker.template.Configuration instance as the configuration. The option is a freemarker.template.Configuration type. String camel.component.freemarker.enabled Enable freemarker component true Boolean camel.component.freemarker.resolve-property-placeholders Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. true Boolean 110.4. Headers Headers set during the FreeMarker evaluation are returned to the message and added as headers. This provides a mechanism for the FreeMarker component to return values to the Message. An example: Set the header value of fruit in the FreeMarker template: USD{request.setHeader('fruit', 'Apple')} The header, fruit , is now accessible from the message.out.headers . 110.5. FreeMarker Context Camel will provide exchange information in the FreeMarker context (just a Map ). The Exchange is transferred as: key value exchange The Exchange itself. exchange.properties The Exchange properties. headers The headers of the In message. camelContext The Camel Context. request The In message. body The In message body. response The Out message (only for InOut message exchange pattern). From Camel 2.14, you can setup your custom FreeMarker context in the message header with the key " CamelFreemarkerDataModel " just like this Map<String, Object> variableMap = new HashMap<String, Object>(); variableMap.put("headers", headersMap); variableMap.put("body", "Monday"); variableMap.put("exchange", exchange); exchange.getIn().setHeader("CamelFreemarkerDataModel", variableMap); 110.6. Hot reloading The FreeMarker template resource is by default not hot reloadable for both file and classpath resources (expanded jar). If you set contentCache=false , then Camel will not cache the resource and hot reloading is thus enabled. This scenario can be used in development. 110.7. Dynamic templates Camel provides two headers by which you can define a different resource location for a template or the template content itself. If any of these headers is set then Camel uses this over the endpoint configured resource. This allows you to provide a dynamic template at runtime. Header Type Description Support Version FreemarkerConstants.FREEMARKER_RESOURCE org.springframework.core.io.Resource The template resource ⇐ 2.1 FreemarkerConstants.FREEMARKER_RESOURCE_URI String A URI for the template resource to use instead of the endpoint configured. >= 2.1 FreemarkerConstants.FREEMARKER_TEMPLATE String The template to use instead of the endpoint configured. >= 2.1 110.8. Samples For example you could use something like: from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl"); To use a FreeMarker template to formulate a response for a message for InOut message exchanges (where there is a JMSReplyTo header). If you want to use InOnly and consume the message and send it to another destination you could use: from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl"). to("activemq:Another.Queue"); And to disable the content cache, e.g. for development usage where the .ftl template should be hot reloaded: from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl?contentCache=false"). to("activemq:Another.Queue"); And a file-based resource: from("activemq:My.Queue"). to("freemarker:file://myfolder/MyResponse.ftl?contentCache=false"). to("activemq:Another.Queue"); In Camel 2.1 it's possible to specify what template the component should use dynamically via a header, so for example: from("direct:in"). setHeader(FreemarkerConstants.FREEMARKER_RESOURCE_URI).constant("path/to/my/template.ftl"). to("freemarker:dummy?allowTemplateFromHeader=true"); Warning Enabling the allowTemplateFromHeader option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. 110.9. The Email Sample In this sample we want to use FreeMarker templating for an order confirmation email. The email template is laid out in FreeMarker as: Dear USD{headers.lastName}, USD{headers.firstName} Thanks for the order of USD{headers.item}. Regards Camel Riders Bookstore USD{body} And the java code: 110.10. See Also Configuring Camel Component Endpoint Getting Started
<dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-freemarker</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency> freemarker:templateName[?options] freemarker:resourceUri USD{request.setHeader('fruit', 'Apple')} Map<String, Object> variableMap = new HashMap<String, Object>(); variableMap.put("headers", headersMap); variableMap.put("body", "Monday"); variableMap.put("exchange", exchange); exchange.getIn().setHeader("CamelFreemarkerDataModel", variableMap); from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl"); from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl"). to("activemq:Another.Queue"); from("activemq:My.Queue"). to("freemarker:com/acme/MyResponse.ftl?contentCache=false"). to("activemq:Another.Queue"); from("activemq:My.Queue"). to("freemarker:file://myfolder/MyResponse.ftl?contentCache=false"). to("activemq:Another.Queue"); from("direct:in"). setHeader(FreemarkerConstants.FREEMARKER_RESOURCE_URI).constant("path/to/my/template.ftl"). to("freemarker:dummy?allowTemplateFromHeader=true"); Dear USD{headers.lastName}, USD{headers.firstName} Thanks for the order of USD{headers.item}. Regards Camel Riders Bookstore USD{body}