[CONF] Apache Camel > Velocity

[confluence]

Velocity Page edited by Jonathan Anstey Velocity The velocity: component allows you to process a message using an Apache Velocity template. This can be ideal when using Templating to generate responses for requests. URI format velocity:templateName[?options] Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (eg: file://folder/myfile.vm). You can append query options to the URI in the following format, ?option=value&option=value&... Options Option Default Description loaderCache true Velocity based file loader cache. contentCache   New option in Camel 1.4: Cache for the resource content when it is loaded. By default, it's false in Camel 1.x. By default, it's true in Camel 2.x. encoding null New option in Camel 1.6: Character encoding of the resource content. Message Headers The velocity component sets a couple headers on the message (you can't set these yourself): Header Description org.apache.camel.velocity.resource Camel 1.x: The resource as an org.springframework.core.io.Resource object. org.apache.camel.velocity.resourceUri Camel 1.x: The templateName as a String object. CamelVelocityResource Camel 2.0: The resource as an org.springframework.core.io.Resource object. CamelVelocityResourceUri Camel 2.0: The templateName as a String object. In Camel 1.4 headers set during the Velocity evaluation are returned to the message and added as headers. Then its kinda possible to return values from Velocity to the Message. For example, to set the header value of fruit in the Velocity template .tm: $in.setHeader('fruit', 'Apple') The fruit header is now accessible from the message.out.headers. Velocity Context Camel will provide exchange information in the Velocity context (just a Map). The Exchange is transfered as: key value exchange The Exchange itself. headers The headers of the In message. camelContext The Camel Context intance. 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). Hot reloading The Velocity template resource is, by default, hot reloadable for both file and classpath resources (expanded jar). If you set contentCache=true, Camel will only load the resource once, and thus hot reloading is not possible. This scenario can be used in production, when the resource never changes. Samples For example you could use something like from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm"); To use a Velocity template to formulate a response to a message for InOut message exchanges (where there is a JMSReplyTo header). If you want to use InOnly and consume the message and send it to another destination, you could use the following route: from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm"). to("activemq:Another.Queue"); And to use the content cache, e.g. for use in production, where the .vm template never changes: from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue"); And a file based resource: from("activemq:My.Queue"). to("velocity:file://myfolder/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue"); The Email Sample In this sample we want to use Velocity templating for an order confirmation email. The email template is laid out in Velocity 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; } @Test 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\nPS: 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("velocity:org/apache/camel/component/velocity/letter.vm").to("mock:result"); } }; } See Also Configuring Camel Component Endpoint Getting Started Change Notification Preferences View Online | View Change | Add Comment