[CONF] Apache Camel: StringTemplate (page edited)

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[CONF] Apache Camel: StringTemplate (page edited)

Dhiraj Bokde (Confluence)

StringTemplate has been edited by Claus Ibsen (Jun 05, 2008).

(View changes)

Content:

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.

URI format

string-template:templateName

Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template.

Options

Option Default Description
contentCache false New option in Camel 1.4. Cache for the resource content when its loaded.

Headers

Camel will store a reference to the resource in the message header in the key org.apache.camel.stringtemplate.resource. The Resource is an org.springframework.core.io.Resource object.

Hot reloading

The stringtemplate resource is by default hot reloadable for both file and classpath resources (expanded jar). Setting the contentCache=true then Camel will only load the resource once, and thus hot reloading is not possible. This scenario can be used in production usage when the resource never changes.

Velocity Content

Camel will provide exchange information in the velocity context (just a Map). The Exchange is transfered to the VelocityContext as:

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)

Samples

For example you could use something like

from("activemq:My.Queue").
  to("string-template:com/acme/MyResponse.tm");

To use a string template to formulate a response for a message

The Email Sample

In this sample we want to use StringTemplate as templating for an order confirmation email. The email template is laid out in StringTemplate as:

Dear $headers.lastName$, $headers.firstName$

Thanks for the order of $headers.item$.

Regards Camel Riders Bookstore

And the java code:

private Exchange createLetter() {
    Exchange exchange = context.getEndpoint("direct:a").createExchange();
    Message msg = exchange.getIn();
    msg.setHeader("firstName", "Claus");
    msg.setHeader("lastName", "Ibsen");
    msg.setHeader("item", "Camel in Action");
    return exchange;
}

public void testVelocityLetter() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedBodiesReceived("Dear Ibsen, Claus\n\nThanks for the order of Camel in Action.\n\nRegards Camel Riders Bookstore");

    template.send("direct:a", createLetter());

    mock.assertIsSatisfied();
}

protected RouteBuilder createRouteBuilder() throws Exception {
    return new RouteBuilder() {
        public void configure() throws Exception {
            from("direct:a").to("string-template:org/apache/camel/component/stringtemplate/letter.tm").to("mock:result");
        }
    };
}

See Also