camel: how can i send to an endpoint asynchronously

Question

How can I send a message to an endpoint without waiting for that endpoint's route to be process (that is, my route should just dispatch the message and finish)?

Answer 1

Using wireTap or multicast is what you're after. A direct: endpoint will modify the Exchange for the next step no matter what ExchangePattern is specified. You can see by using this failing test:

public class StackOverflowTest extends CamelTestSupport {
    private static final String DIRECT_INPUT = "direct:input";
    private static final String DIRECT_NO_RETURN = "direct:no.return";
    private static final String MOCK_OUTPUT = "mock:output";
    private static final String FIRST_STRING = "FIRST";
    private static final String SECOND_STRING = "SECOND";

    @NotNull
    @Override
    protected RouteBuilder createRouteBuilder() throws Exception {
        return new RouteBuilder() {
            @Override
            public void configure() throws Exception {
                from(DIRECT_INPUT)
                        .to(ExchangePattern.InOnly, DIRECT_NO_RETURN)
                        .to(MOCK_OUTPUT)
                        .end();

                from(DIRECT_NO_RETURN)
                        .bean(new CreateNewString())
                        .end();
            }
        };
    }

    @Test
    public void testShouldNotModifyMessage() throws JsonProcessingException, InterruptedException {
        final MockEndpoint myMockEndpoint = getMockEndpoint(MOCK_OUTPUT);
        myMockEndpoint.expectedBodiesReceived(FIRST_STRING);
        template.sendBody(DIRECT_INPUT, FIRST_STRING);
        assertMockEndpointsSatisfied();
    }

    public static class CreateNewString {
        @NotNull
        public String handle(@NotNull Object anObject) {
            return SECOND_STRING;
        }
    }
}

Now if you change the above to a wireTap:

                from(DIRECT_INPUT)
                    .wireTap(DIRECT_NO_RETURN)
                    .to(MOCK_OUTPUT)
                    .end();

and you'll see it works as expected. You can also use multicast:

                from(DIRECT_INPUT)
                    .multicast()
                    .to(DIRECT_NO_RETURN)
                    .to(MOCK_OUTPUT)
                    .end();