In studying for my SCJA a majority of the study guides ive seen state that JMS uses Asynchronous messaging. However i came across the following statement which hints that JMS can do both Asynchronous and Synchronous:
2.3 Message Consumption
Messaging products are inherently asynchronous in that no fundamental timing dependency exists between the production and the consumption of a message. However, the JMS Specification uses this term in a more precise sense. Messages can be consumed in either of two ways:
Synchronously. A subscriber or a receiver explicitly fetches the message from the destination by calling the receive method. The receive method can block until a message arrives or can time out if a message does not arrive within a specified time limit.
Asynchronously. A client can register a message listener with a consumer. A message listener is similar to an event listener. Whenever a message arrives at the destination, the JMS provider delivers the message by calling the listener's onMessage method, which acts on the contents of the message.
am I just interpreting this wrong?
SCJA, ITIL V3 Foudation, Studying for SCJP6
Joined: Apr 11, 2009
Both above statements are true. However most of times Asynchronous messgaing is used with JMS. Idea about asynchronous can be best understood if transaction scope and boundary.
Event If a receiver is calling receive message method in blocking mode, still it will not be part of sender's transaction.
Joined: Aug 12, 2009
JMS architecture provides two types of messaging by default. Asynchronous and synchronous method.
There are two destinations which allow you to do both type of messaging. Queue and Topic.
Queue supports asynchronous messaging by Point to point messaging.
Topic supports synchronous messaging by publish/subcriber messaging. So if you want asynchronous messaging in Topic, you can implement MessageListener interface.