These are the key features of message-driven beans:

• Clients do not access message-driven beans through interfaces. A message-driven bean has only a bean class.

• A message-driven bean's instances retain no data or conversational state for a specific client. All instances of a message-driven bean are equivalent, allowing the EJB container to assign a message to any message-driven bean instance. The container can pool these instances to allow streams of messages to be processed concurrently.

When a message arrives, the container calls the message-driven bean's onMessage method to process the message. The onMessage method may call helper methods, or it may invoke a session or entity bean to process the information in the message or to store it in a database.

A message may be delivered to a message-driven bean within a transaction context, so that all operations within the onMessage method are part of a single transaction. If message processing is rolled back, the message will be re-delivered.

For information about design alternatives for message-driven beans, see MDBs and Messaging Models.

For a description of the overall EJB development process, see Developing Enterprise JavaBeans for Oracle WebLogic Server.

• JCA-Based MDBs
  Learn how to configure MDBs to receive messages from JCA 1.7-compliant resource adapters and to set the resource-adapter-jndi-name deployment descriptor.