[[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[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 2 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
|===
// 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 (5 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
| *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
|===
// 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 3 options, which are listed below.



[width="100%",cols="2,5,^1,2",options="header"]
|===
| 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
|===
// 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).
|=======================================================================

From Camel 2.14, 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%,10%,70%",options="header",]
|=======================================================================
|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
|=======================================================================

### 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");
---------------------------------------------------------------------

In *Camel 2.1* 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
