Composed Message Processor
How can you maintain the overall message flow when processing a message consisting of multiple elements, each of which may require different processing?
Use Composed Message Processor to process a composite message. The Composed Message Processor splits the message up, routes the sub-messages to the appropriate destinations and re-aggregates the responses back into a single message.
With Camel this pattern is implemented by the Splitter which has built-in aggregation to re-aggregate the responses back into a single message.
This example uses the Split EIP as composed message processor to process each split message, aggregate and return a single combined response.
The route and the code comments below explains how you can use the Split EIP to split each message to sub-message which are processed individually and then combined back into a single response message via the custom
MyOrderStrategy), as the output from the Split EIP.
// this routes starts from the direct:start endpoint // the body is then split based on @ separator // the splitter in Camel supports InOut as well and for that we need // to be able to aggregate what response we need to send back, so we provide our // own strategy with the class MyOrderStrategy. from("direct:start") .split(body().tokenize("@"), new MyOrderStrategy()) // each split message is then send to this bean where we can process it .to("bean:MyOrderService?method=handleOrder") // this is important to end the splitter route as we do not want to do more routing // on each split message .end() // after we have split and handled each message we want to send a single combined // response back to the original caller, so we let this bean build it for us // this bean will receive the result of the aggregate strategy: MyOrderStrategy .to("bean:MyOrderService?method=buildCombinedResponse")
See the Splitter EIP.