Whereas the MessageHandler interface provides the foundation for many of the components that enable non-invasive invocation of your application code from the messaging system, sometimes it is necessary to invoke the messaging system from your application code. Spring Integration provides a MessageExchangeTemplate that supports a variety of message-exchanges, including request/reply scenarios. For example, it is possible to send a request and wait for a reply.

MessageExchangeTemplate template = new MessageExchangeTemplate();
Message reply = template.sendAndReceive(new StringMessage("test"), someChannel);

In that example, a temporary anonymous channel would be created internally by the template. The 'sendTimeout' and 'receiveTimeout' properties may also be set on the template, and other exchange types are also supported.

public boolean send(final Message<?> message, final MessageTarget target) { ... }

public Message<?> sendAndReceive(final Message<?> request, final MessageTarget target) { .. }

public Message<?> receive(final PollableSource<?> source) { ... }

public boolean receiveAndForward(final PollableSource<?> source, final MessageTarget target) { ... }

Additionally, a 'transactionManager' can be configured on a MessageExchangeTemplate as well as the various transaction attributes:

template.setTransactionManager(transactionManager);
template.setPropagationBehaviorName(propagationBehavior);
template.setIsolationLevelName(isolationLevel);
template.setTransactionTimeout(transactionTimeout);
template.setTransactionReadOnly(readOnly);
template.setReceiveTimeout(receiveTimeout);
template.setSendTimeout(sendTimeout);

Finally, there is a also an asynchronous version called AsyncMessageExchangeTemplate whose constructor accepts a TaskExecutor, and whose Message-returning methods return an AsyncMessage. That is essentially a wrapper for any Message that also implements Future<Message<T>>:

AsyncMessageExchangeTemplate template = new AsyncMessageExchangeTemplate(taskExecutor);
Message reply = template.sendAndReceive(new StringMessage("test"), someChannel);
// do some work in the meantime
reply.getPayload(); // blocks if still waiting for actual reply