Chapter 46. FreeMarker

FreeMarker
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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 your Camel core version -->
</dependency>

<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>

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URI format
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freemarker:templateName[?options]

freemarker:templateName[?options]

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Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (for example, file://folder/myfile.ftl).

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

Options
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Option	Default	Description
`contentCache`	`true`	Cache for the resource content when it's loaded. Note: as of Camel 2.9 cached resource content can be cleared via JMX using the endpoint's `clearContentCache` operation.
`encoding`	`null`	Character encoding of the resource content.
`templateUpdateDelay`	`5`	Camel 2.9: Number of seconds the loaded template resource will remain in the cache.

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

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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 set up your custom FreeMarker context in the message header with the key, CamelFreemarkerDataModel, 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);

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);

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Hot reloading
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The FreeMarker template resource is by default not hot reloadable for both file and classpath resources (expanded jar). If you set contentCache=false, then Apache Camel will not cache the resource and hot reloading is thus enabled. This scenario can be used in development.

Dynamic templates
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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.

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Header	Type	Description	Support Version
`FreemarkerConstants.FREEMARKER_RESOURCE`	`org.springframework.core.io.Resource`	The template resource	<= 1.6.2, <= 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
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For example, you can define a route like the following:

from("activemq:My.Queue").
  to("freemarker:com/acme/MyResponse.ftl");

from("activemq:My.Queue").
  to("freemarker:com/acme/MyResponse.ftl");

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To use a FreeMarker template to formulate a response to InOut message exchanges (where there is a JMSReplyTo header).

If you want to process InOnly exchanges, you could use a FreeMarker template to transform the message before sending it on to another endpoint:

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:com/acme/MyResponse.ftl").
  to("activemq:Another.Queue");

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:com/acme/MyResponse.ftl").
  to("activemq:Another.Queue");

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And to disable the content cache (for example, for development usage where the .ftl template should be hot reloaded):

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:com/acme/MyResponse.ftl?contentCache=false").
  to("activemq:Another.Queue");

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:com/acme/MyResponse.ftl?contentCache=false").
  to("activemq:Another.Queue");

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And for a file-based resource:

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:file://myfolder/MyResponse.ftl?contentCache=false").
  to("activemq:Another.Queue");

from("activemq:My.Queue").
  to(ExchangePattern.InOut,"freemarker:file://myfolder/MyResponse.ftl?contentCache=false").
  to("activemq:Another.Queue");

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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");

from("direct:in").
  setHeader(FreemarkerConstants.FREEMARKER_RESOURCE_URI).constant("path/to/my/template.ftl").
  to("freemarker:dummy");

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The Email Sample
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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}

Dear ${headers.lastName}, ${headers.firstName}

Thanks for the order of ${headers.item}.

Regards Camel Riders Bookstore
${body}

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And the java code:

private Exchange createLetter() {
    Exchange exchange = context.getEndpoint("direct:a").createExchange();
    Message msg = exchange.getIn();
    msg.setHeader("firstName", "Claus");
    msg.setHeader("lastName", "Ibsen");
    msg.setHeader("item", "Camel in Action");
    msg.setBody("PS: Next beer is on me, James");
    return exchange;
}

@Test
public void testFreemarkerLetter() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedBodiesReceived("Dear Ibsen, Claus\n\nThanks for the order of Camel in Action."
      + "\n\nRegards Camel Riders Bookstore\nPS: Next beer is on me, James");

    template.send("direct:a", createLetter());

    mock.assertIsSatisfied();
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            from("direct:a")
                .to("freemarker:org/apache/camel/component/freemarker/letter.ftl")
                .to("mock:result");
        }
    };
}

private Exchange createLetter() {
    Exchange exchange = context.getEndpoint("direct:a").createExchange();
    Message msg = exchange.getIn();
    msg.setHeader("firstName", "Claus");
    msg.setHeader("lastName", "Ibsen");
    msg.setHeader("item", "Camel in Action");
    msg.setBody("PS: Next beer is on me, James");
    return exchange;
}

@Test
public void testFreemarkerLetter() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedBodiesReceived("Dear Ibsen, Claus\n\nThanks for the order of Camel in Action."
      + "\n\nRegards Camel Riders Bookstore\nPS: Next beer is on me, James");

    template.send("direct:a", createLetter());

    mock.assertIsSatisfied();
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            from("direct:a")
                .to("freemarker:org/apache/camel/component/freemarker/letter.ftl")
                .to("mock:result");
        }
    };
}

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FreeMarker
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URI format
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Options
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FreeMarker Context
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Hot reloading
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Dynamic templates
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Samples
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The Email Sample
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Chapter 46. FreeMarker

FreeMarkerCopiar o linkLink copiado para a área de transferência!

URI formatCopiar o linkLink copiado para a área de transferência!

OptionsCopiar o linkLink copiado para a área de transferência!

FreeMarker ContextCopiar o linkLink copiado para a área de transferência!

Hot reloadingCopiar o linkLink copiado para a área de transferência!

Dynamic templatesCopiar o linkLink copiado para a área de transferência!

SamplesCopiar o linkLink copiado para a área de transferência!

The Email SampleCopiar o linkLink copiado para a área de transferência!

Aprender

Experimente, compre e venda

Comunidades

Sobre a documentação da Red Hat

Tornando o open source mais inclusivo

Sobre a Red Hat

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links

FreeMarker
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URI format
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Options
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FreeMarker Context
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Hot reloading
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Dynamic templates
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Samples
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The Email Sample
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