[CONF] Apache Camel: Freemarker (page edited)

Thu, 22 Jan 2009 05:51:34 -0800

Page Edited : CAMEL : Freemarker

Freemarker has been edited by Claus Ibsen (Jan 22, 2009).

(View changes)

Content:

Freemarker

Available as of Camel 1.6

The freemarker: component allows you to process a message using a Freemarker template. This can be ideal when using Templating to generate responses for requests.

URI format

freemarker:templateName

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).



Options






 Option 
 Default 
 Description 




 contentCache 
 true 
 Cache for the resource content when its loaded. 




 encoding 
 null 
 Character encoding of the resource content. 






Headers


Camel will store a reference to the resource in the message header in the key org.apache.camel.freemarker.resource. The Resource is an org.springframework.core.io.Resource object. And the key org.apache.camel.freemarker.resourceUri holds the templateName as a String object.



Headers set during the Freemarker evaluation is returned to the message and added as headers. Then its kinda possible to return values from Freemarker to the Message.



An example: Set the header value of fruit in the Freemarker template:




${request.setHeader('fruit', 'Apple')}





The header 'fruit' is now accessible from the message.out.headers.



Velocity Context


Camel will provide exchange information in the Freemarker context (just a Map). The Exchange is transfered as:





 key 
 value 




 exchange 
 The Exchange itself 




 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) 






Hot reloading


The Freemarker template resource is by default not hot reloadable for both file and classpath resources (expanded jar). Setting the contentCache=false then Camel will not cache the resource and hot reloading is thus enabled. This scenario can be used in development usage.



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, eg. 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");





The Email Sample


In this sample we want to use Freemarker as templating for an order confirmation email. The email template is laid out in Freemarker as:




Dear ${headers.lastName}, ${headers.firstName}

Thanks for the order of ${headers.item}.

Regards Camel Riders Bookstore
${body}





And the java code:





private Exchange createLetter() {
    Exchange exchange = context.getEndpoint("direct:a").createExchange();
    Message msg = exchange.getIn();
    msg.setHeader("firstName", "Claus");
    msg.setHeader("lastName", "Ibsen");
    msg.setHeader("item", "Camel in Action");
    msg.setBody("PS: Next beer is on me, James");
    return exchange;
}

public void testFreemarkerLetter() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedBodiesReceived("Dear Ibsen, Claus\n\nThanks for the order of Camel in Action.\n\nRegards Camel Riders Bookstore\nPS: Next beer is on me, James");

    template.send("direct:a", createLetter());

    mock.assertIsSatisfied();
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            from("direct:a").to("freemarker:org/apache/camel/component/freemarker/letter.ftl").to("mock:result");
        }
    };
}





See Also

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