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:

<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}} | *Since Camel 2.11.1*, configuring the variable start delimiter |
| {{delimiterStop}} | {{null}} | *Since Camel 2.11.1*, configuring the variable end delimiter |
{div}

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 loads the resource only once and hot-reloading is not possible. 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 transfered 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). |
{div}

Since Camel 2.14, you can define the custom context map by setting the message header "CamelStringTemplateVariableMap" just like the below code.

Map<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}