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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>
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311.1. URI format
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string-template: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.

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

311.2. Options
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The String Template component has no options.

The String Template endpoint is configured using URI syntax: 

string-template:resourceUri
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with the following path and query parameters:

311.2.1. Path Parameters (1 parameters):
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Expand
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):
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Expand
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
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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
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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
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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);
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311.6. Samples
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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");
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311.7. The Email Sample
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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>
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And the java code is as follows:

311.8. See Also
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  • Configuring Camel
  • Component
  • Endpoint
  • Getting Started
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