FreeMarker

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.

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 for the camel-core artifact -->
</dependency>

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&...

Options

Headers

This only applies to versions before Camel 1.6.2 and Camel 2.1

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 are 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.

FreeMarker Context

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

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

Available as of Camel 2.1

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.

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");

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 ${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