Messaging products are inherently asynchronous. However in JMS, messages can be consumed in either of the two ways:

• Synchronously: A subscriber or a receiver explicitly fetches the message from the destination by calling the receive 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.