Posted in: EJB Interview Questions with Answers
Message driven bean process messages asynchronously are deliver via JMS. M.D.B’s are
stateless, server side, transaction aware components used for
asynchronous JMS messages. It acts as a JMS message listener which JMS
messages, the messages may be sent by any J2ee component, an application
client, another enterprise bean, or by a JMS application.
When
EJB application server starts it parse the D.D and then loads and
initializes declared beans. In case of M.D.B container establish a
connection with the message provide(MOM server), client access message
beans through the beans JMS interface (java.JMS.messageListerner) which
exposes a single method.
Message driven bean’s life cycle
- EJB container creates a pool of message-driven bean instances
- For each instance, the EJB container instantiates the bean :
- It calls the setMessageDrivenContext
- It calls the instance's ejbCreate
- Like a stateless session bean,it’s never passivated, It has only two states:
- Nonexistent
- Ready to receive messages.
- is only a bean class – no interfaces
- While in the ready state :
- EJB container may call onMessage
- EJB container may call the ejbRemove