docs/components/modules/ROOT/pages/freemarker-component.adoc

[[freemarker-component]]
= Freemarker Component
:page-source: components/camel-freemarker/src/main/docs/freemarker-component.adoc

*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 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
| *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 3 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
|===
// 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: