Freemarker

Since Camel 2.10

Only producer is supported

The freemarker: component allows for processing 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 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).

You can append query options to the URI in the following format, ?option=value&option=value&…​

Options

The Freemarker component supports 6 options, which are listed below.

Name Description Default Type

allowContextMapAll (producer)

Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API.

false

boolean

allowTemplateFromHeader (producer)

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

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

localizedLookup (producer)

Enables/disables localized template lookup. Disabled by default.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

configuration (advanced)

To use an existing freemarker.template.Configuration instance as the configuration.

Configuration

The Freemarker endpoint is configured using URI syntax:

freemarker:resourceUri

with the following path and query parameters:

Path Parameters (1 parameters):

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):

Name Description Default Type

allowContextMapAll (producer)

Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API.

false

boolean

allowTemplateFromHeader (producer)

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

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

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:

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

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.

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:

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");

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?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}

And the java code:

Spring Boot Auto-Configuration

When using freemarker with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-freemarker-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 7 options, which are listed below.

Name Description Default Type

camel.component.freemarker.allow-context-map-all

Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API.

false

Boolean

camel.component.freemarker.allow-template-from-header

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

Boolean

camel.component.freemarker.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.freemarker.configuration

To use an existing freemarker.template.Configuration instance as the configuration. The option is a freemarker.template.Configuration type.

Configuration

camel.component.freemarker.enabled

Whether to enable auto configuration of the freemarker component. This is enabled by default.

Boolean

camel.component.freemarker.lazy-start-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

camel.component.freemarker.localized-lookup

Enables/disables localized template lookup. Disabled by default.

false

Boolean
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