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.

string-template:templateName

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

FUSE Mediation Router 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.

The stringtemplate resource is by default hot reloadable for both file and classpath resources (expanded jar). Setting the contentCache=true then FUSE Mediation Router 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.

FUSE Mediation Router will provide exchange information as attributes (just a Map) to the string template. The Exchange is transfered as:

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

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
$body$

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");
    msg.setBody("PS: Next beer is on me, James");
    return exchange;
}

public void testVelocityLetter() throws Exception {
    MockEndpoint mock = getMockEndpoint("mock:result");
    mock.expectedMessageCount(1);
    mock.expectedBodiesReceived("Dear Ibsen, Claus! Thanks for the order of Camel in Action. Regards Camel Riders Bookstore PS: Next beer is on me, James");

    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");
        }
    };
}