= Freemarker Component
:doctitle: Freemarker
:shortname: freemarker
:artifactid: camel-freemarker
:description: Transform messages using FreeMarker templates.
:since: 2.10
:supportlevel: Stable
:component-header: Only producer is supported
//Manually maintained attributes
:camel-spring-boot-name: freemarker

*Since Camel {since}*

*{component-header}*

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

---------------------------------
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`).


// component-configure options: START

// component-configure options: END

// component options: START
include::partial$component-configure-options.adoc[]
include::partial$component-endpoint-options.adoc[]
// component options: END

// endpoint options: START

// endpoint 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:

--------------------------------------
${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?allowTemplateFromHeader=true");
---------------------------------------------------------------------------------------------

== 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}
----------------------------------------------



include::spring-boot:partial$starter.adoc[]
