使用Apache Camel的带有RequestReply的RecipientList

Question

I think that I have a gap in my understanding of the RecipientList . My understanding is that RecipientList EIP can be used to represent dynamic destinations. I am attempting to use is with the RequestReply EIP but I am getting some strange results.

The code below is a unit test for RequestReply and aggregation of replies back to the sender. Message arrives at incomingMessages1-update, gets routed to outgoingMessages-[123]-update queues. The results come back on outgoingMessages-[123]-reply queues. The results are aggregated and sent back on incomingMessages1-reply queue.

See below a unit test that works:

public class AggregateStrategyTestOnMultipleReplyQueues extends CamelTestSupport {

@Test
public void testRequestReplyWithRecipientListAndCustomGather()
        throws Exception {
    int numberOfMessages = 5;
    getMockEndpoint("mock:end").setExpectedMessageCount(numberOfMessages);

    context.addRoutes(new RouteBuilder() {
        public void configure() throws Exception {
            from("jms:incomingMessages1-update")
                .multicast(new GatherResponses())
                    .to("jms:outgoingMessages1-update?exchangePattern=InOut&replyTo=queue:outgoingMessages1-reply&preserveMessageQos=true") //1
                    .to("jms:outgoingMessages2-update?exchangePattern=InOut&replyTo=queue:outgoingMessages2-reply&preserveMessageQos=true") //2
                    .to("jms:outgoingMessages3-update?exchangePattern=InOut&replyTo=queue:outgoingMessages3-reply&preserveMessageQos=true") //3
                    .to("mock:end");

            //this is what the adapters will be doing
            from("jms:outgoingMessages1-update").setBody(constant("Hello World")).to(
                    "mock:end");
            from("jms:outgoingMessages2-update").setBody(constant("Welcome World")).to(
                    "mock:end");
            from("jms:outgoingMessages3-update").setBody(constant("Hi World")).to(
                    "mock:end");
        }
    });

    String messageSent = "Message sent from template";

    Object response = template
            .requestBodyAndHeader(
                    "jms:incomingMessages1-update?exchangePattern=InOut&preserveMessageQos=true",
                    messageSent, "JMSReplyTo", "incomingMessages1-reply");
    assertEquals("Hello World" + " "+ "Welcome World"+ " "+ "Hi World"+ " " + messageSent ,
            response);

    }

    private class GatherResponses implements AggregationStrategy {
        public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
            if (oldExchange == null) {
                return newExchange;
            }
            String oldBody = oldExchange.getIn().getBody(String.class);
            String newBody = newExchange.getIn().getBody(String.class);
            String body = oldBody + " " + newBody;
            oldExchange.getIn().setBody(body);
            return oldExchange;
        }
    }
}    

I attempted to change the code above (//1, //2 and //3 to a recipient list like below) and it didn't work:

from("jms:incomingMessages1-update")
                    .recipientList(header("myRecipientList")).aggregationStrategy(new GatherResponses()).parallelProcessing().end()
                    .to("mock:end");

I loaded the URIs like this:

List<String> recipientList = new ArrayList<String>();
recipientList.add("jms:outgoingMessages1-update?exchangePattern=InOut&replyTo=queue:outgoingMessages1-reply&preserveMessageQos=true");
recipientList.add("jms:outgoingMessages2-update?exchangePattern=InOut&replyTo=queue:outgoingMessages1-reply&preserveMessageQos=true");
recipientList.add("jms:outgoingMessages3-update?exchangePattern=InOut&replyTo=queue:outgoingMessages1-reply&preserveMessageQos=true");

Map<String, Object> headers = new HashMap<String, Object>();
headers.put("JMSReplyTo", "incomingMessages1-reply");
headers.put("myRecipientList", recipientList);

I am getting the original message back and I am not seeing the reply queues created. Can you please point me to what I am missing?

Answer 1

You cannot send a List/Map etc as JMS headers. The JMS spec does not allow that.

See section Message format when sending at

• http://camel.apache.org/jms

And also the JMS spec / api / javadoc etc.

You can instead store the values in a String separated by comma. The Camel recipient list will automatic use comma as delimiter, so that should then work out of the box.