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String Template

The string-template: component allows you to process a message using a String 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:

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

URI Format

string-template:templateName[?options]

Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template.

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

false

Cache for the resource content when its loaded.
Note: as of Camel 2.9 cached resource content can be cleared via JMX using the endpoint's clearContentCache operation.

delimiterStart

null

From Camel 2.11.1: configuring the variable start delimiter

delimiterStop

null

From Camel 2.11.1: configuring the variable end delimiter

Headers

Camel will store a reference to the resource in the message header with key, org.apache.camel.stringtemplate.resource. The Resource is an org.springframework.core.io.Resource object.

Hot-Reloading

The string template resource is by default hot-reloadable for both file and classpath resources (expanded jar). If you set contentCache=true, Camel will load the resource just once, disabling hot-reloading. This scenario can be used in production when the resource never changes.

StringTemplate Attributes

Camel will provide exchange information as attributes (just a java.util.Map) to the string template. The Exchange is transferred as:

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Key

Value

exchange

The Exchange itself.

headers

The headers of the IN message.

camelContext

The Camel Context.

request

The IN message.

in

The IN message.

body

The IN message body.

out

The OUT message (only for InOut message exchange pattern).

response

The OUT message (only for InOut message exchange pattern).

From Camel 2.14: you can define the custom context map by setting the message header CamelStringTemplateVariableMap, as shown below:

javaMap<String, Object> variableMap = new HashMap<String, Object>(); Map<String, Object> headersMap = new HashMap<String, Object>(); headersMap.put("name", "Willem"); variableMap.put("headers", headersMap); variableMap.put("body", "Monday"); variableMap.put("exchange", exchange); exchange.getIn().setHeader("CamelStringTemplateVariableMap", variableMap);

Samples

For example you could use a string template as follows in order to formulate a response to a message:

from("activemq:My.Queue") .to("string-template:com/acme/MyResponse.tm");

The Email Sample

In this sample we want to use a string template to send an order confirmation email. The email template is laid out in StringTemplate as:
This example works for camel 2.11.0. If your camel version is less than 2.11.0, the variables should be started and ended with $.

Dear <headers.lastName>, <headers.firstName> Thanks for the order of <headers.item>. Regards Camel Riders Bookstore <body>

And the java code is as follows:{snippet:id=e1|lang=java|url=camel/trunk/components/camel-stringtemplate/src/test/java/org/apache/camel/component/stringtemplate/StringTemplateLetterTest.java}Endpoint See Also

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