| [[freemarker-component]] |
| == Freemarker Component |
| |
| *Available as of Camel version 2.10* |
| |
| The *freemarker:* component allows for processing a message using a |
| http://freemarker.org/[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: |
| |
| [source,xml] |
| ------------------------------------------------------------------------------------- |
| <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> |
| ------------------------------------------------------------------------------------- |
| |
| ### URI format |
| |
| [source,java] |
| --------------------------------- |
| 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&...` |
| |
| ### Options |
| |
| |
| |
| |
| // component options: START |
| The Freemarker component supports 3 options, which are listed below. |
| |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *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 |
| | *basicPropertyBinding* (advanced) | Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | boolean |
| |=== |
| // component options: END |
| |
| |
| |
| |
| |
| // endpoint options: START |
| The Freemarker endpoint is configured using URI syntax: |
| |
| ---- |
| freemarker:resourceUri |
| ---- |
| |
| with the following path and query parameters: |
| |
| ==== Path Parameters (1 parameters): |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | 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 |
| |=== |
| |
| |
| ==== Query Parameters (7 parameters): |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *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 |
| | *lazyStartProducer* (producer) | Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel's routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. | false | boolean |
| | *templateUpdateDelay* (producer) | Number of seconds the loaded template resource will remain in the cache. | | int |
| | *basicPropertyBinding* (advanced) | Whether the endpoint should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | boolean |
| | *synchronous* (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean |
| |=== |
| // endpoint options: END |
| // spring-boot-auto-configure options: START |
| === Spring Boot Auto-Configuration |
| |
| When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration: |
| |
| [source,xml] |
| ---- |
| <dependency> |
| <groupId>org.apache.camel</groupId> |
| <artifactId>camel-freemarker-starter</artifactId> |
| <version>x.x.x</version> |
| <!-- use the same version as your Camel core version --> |
| </dependency> |
| ---- |
| |
| |
| The component supports 4 options, which are listed below. |
| |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *camel.component.freemarker.basic-property-binding* | Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | Boolean |
| | *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 |
| |=== |
| // spring-boot-auto-configure options: END |
| |
| |
| |
| |
| ### 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: |
| |
| [source,java] |
| -------------------------------------- |
| ${request.setHeader('fruit', 'Apple')} |
| -------------------------------------- |
| |
| The header, `fruit`, is now accessible from the `message.out.headers`. |
| |
| ### FreeMarker Context |
| |
| Camel will provide exchange information in the FreeMarker context (just |
| a `Map`). The `Exchange` is transferred as: |
| |
| [width="100%",cols="50%,50%",options="header",] |
| |======================================================================= |
| |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). |
| |======================================================================= |
| |
| You can setup your custom FreeMarker context in the |
| message header with the key "*CamelFreemarkerDataModel*" just like this |
| |
| [source,java] |
| -------------------------------------------------------------------- |
| 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); |
| -------------------------------------------------------------------- |
| |
| ### 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. |
| |
| ### 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. |
| |
| [width="100%",cols="10%,10%,80%",options="header",] |
| |======================================================================= |
| |Header |Type |Description |
| |
| |FreemarkerConstants.FREEMARKER_RESOURCE |org.springframework.core.io.Resource |The template resource. |
| |
| |FreemarkerConstants.FREEMARKER_RESOURCE_URI |String |A URI for the template resource to use instead of the endpoint |
| configured. |
| |
| |FreemarkerConstants.FREEMARKER_TEMPLATE |String |The template to use instead of the endpoint configured. |
| |======================================================================= |
| |
| ### Samples |
| |
| For example you could use something like: |
| |
| [source,java] |
| ------------------------------------------- |
| 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: |
| |
| [source,java] |
| ------------------------------------------- |
| 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: |
| |
| [source,java] |
| -------------------------------------------------------------- |
| from("activemq:My.Queue"). |
| to("freemarker:com/acme/MyResponse.ftl?contentCache=false"). |
| to("activemq:Another.Queue"); |
| -------------------------------------------------------------- |
| |
| And a file-based resource: |
| |
| [source,java] |
| --------------------------------------------------------------------- |
| from("activemq:My.Queue"). |
| to("freemarker:file://myfolder/MyResponse.ftl?contentCache=false"). |
| to("activemq:Another.Queue"); |
| --------------------------------------------------------------------- |
| |
| It's possible to specify what template the component |
| should use dynamically via a header, so for example: |
| |
| [source,java] |
| --------------------------------------------------------------------------------------------- |
| from("direct:in"). |
| setHeader(FreemarkerConstants.FREEMARKER_RESOURCE_URI).constant("path/to/my/template.ftl"). |
| to("freemarker:dummy"); |
| --------------------------------------------------------------------------------------------- |
| |
| ### 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: |
| |
| [source,java] |
| ---------------------------------------------- |
| Dear ${headers.lastName}, ${headers.firstName} |
| |
| Thanks for the order of ${headers.item}. |
| |
| Regards Camel Riders Bookstore |
| ${body} |
| ---------------------------------------------- |
| |
| And the java code: |
| |
| ### See Also |
| |
| * Configuring Camel |
| * Component |
| * Endpoint |
| * Getting Started |