JMS MessageConsumer's messageListener makes push or pull?

Question

What really happens under the hood when i set a messageListener on my queue MessageConsumer object. Does the MessageConsumer object make some sort of polling ehind the scene or this is a real push made by the JMS server?

Java Message Service (O'Reilly Java Series) by David A. Chappell, Richard Monson-Haefel and Mark Richards, p10 CHAPTER1: Point-to-point

The point-to-point messaging model has traditionally been a pullbased or polling-based model, where messages are requested from the queue instead of being pushed to the client automatically

http://docs.oracle.com/javaee/1.4/tutorial/doc/JMS4.html#wp79175

When message delivery begins, the JMS provider automatically calls the message listener's onMessage method whenever a message is delivered.

Thanks, Kod

Answer 1

These two do not contradict each other. P2P is essentially pull-based, in that it is receiver's responsibility to read a message once it is sent by a producer. onMessage() method that you mentioned in your 2nd quote is a notification mechanism used to initiate the pull. These variations also referred to as sync vs async modes of receiving JMS messages, as for example in this chapter in Java Tutorial.