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Chapter 311. String Template Component

Available as of Camel version 1.2

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>

311.1. 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&…​

311.2. Options

The String Template component has no options.

The String Template endpoint is configured using URI syntax: 

string-template:resourceUri

with the following path and query parameters:

311.2.1. Path Parameters (1 parameters):

NameDescriptionDefaultType

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

311.2.2. Query Parameters (4 parameters):

NameDescriptionDefaultType

contentCache (producer)

Sets whether to use resource content cache or not

false

boolean

delimiterStart (producer)

The variable start delimiter

<

char

delimiterStop (producer)

The variable end delimiter

>

char

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

311.3. 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.

311.4. 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.

311.5. StringTemplate Attributes

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);

311.6. 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");

311.7. 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:

311.8. See Also

  • Configuring Camel
  • Component
  • Endpoint
  • Getting Started