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>
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
confluenceTableSmallOption | 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 |
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:
confluenceTableSmallKey | 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
