components/camel-stringtemplate/src/main/docs/string-template-component.adoc

## String Template Component

*Available as of Camel version 1.2*

The *string-template:* component allows you to process a message using a
http://www.stringtemplate.org/[String Template]. This can be ideal when
using link:templating.html[Templating] to generate responses for
requests.

Maven users will need to add the following dependency to their `pom.xml`
for this component:

[source,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

[source,java]
--------------------------------------
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


// component options: START
The String Template component has no options.
// component options: END



// endpoint options: START
The String Template endpoint is configured using URI syntax:

    string-template:resourceUri

with the following path and query parameters:

#### Path Parameters (1 parameters):

[width="100%",cols="2,5,^1,2",options="header"]
|=======================================================================
| Name | Description | Default | Type
| **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
|=======================================================================

#### Query Parameters (4 parameters):

[width="100%",cols="2,5,^1,2",options="header"]
|=======================================================================
| Name | Description | Default | Type
| **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
|=======================================================================
// endpoint options: END


### 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

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

[source,java]
--------------------------------------------------------------------------
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:

[source,java]
-----------------------------------------------
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 $.

[source,java]
--------------------------------------------
Dear <headers.lastName>, <headers.firstName>

Thanks for the order of <headers.item>.

Regards Camel Riders Bookstore
<body>
--------------------------------------------

And the java code is as follows:

### See Also

* link:configuring-camel.html[Configuring Camel]
* link:component.html[Component]
* link:endpoint.html[Endpoint]
* link:getting-started.html[Getting Started]