Question

If I set a MessageListener object for a MessageConsumer, and then call receive() on that consumer, what will happen? Will the provider give the message to receive(), or will it continue to be blocked while the message is processed by the MessageListener object?

Answer 1

You will get an exception, as a Session must be in either asynchronous or synchronous modes. From 4.4.6 of the JMS specification

One consequence of the session’s single-thread-of-control restriction is that a
session with message listeners cannot also be used to synchronously receive
messages. Either the session is dedicated to the thread of control used for
delivery to message listeners or it is dedicated to a thread of control initiated
by client code. It is erroneous to attempt to combine both in the same session.