Friday, March 13, 2009

What is the difference between Message Driven Beans and Stateless

Question :What is the difference between Message Driven Beans and Stateless
Session beans? (EJB)

Answer :In several ways, the dynamic creation and allocation of message-driven
bean instances mimics the behavior of stateless session EJB instances,
which exist only for the duration of a particular method call. However,
message-driven beans are different from stateless session EJBs (and other
types of EJBs) in several significant ways:
§ Message-driven beans process multiple JMS messages asynchronously,
rather than processing a serialized sequence of method calls.
§ Message-driven beans have no home or remote interface, and therefore
cannot be directly accessed by internal or external clients. Clients interact
with message-driven beans only indirectly, by sending a message to a JMS
Queue or Topic.
Note: Only the container directly interacts with a message-driven bean by
creating bean instances and passing JMS messages to those instances as
§ The Container maintains the entire lifecycle of a message-driven bean;
instances cannot be created or removed as a result of client requests or
other API calls.

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