INTERVIEW QUESTIONS J2EE EJB DETAILS

Question: What is the life cycle of MDB?

Answer: The lifetime of an MDB instance is controlled by the container. Only two states exist: Does not exist and Ready , as illustrated in the following figure:



The life of an MDB instance starts when the container invokes newInstance() on the MDB class to create a new instance. Next, the container calls setMessageDrivenContext() followed by ejbCreate() on the instance. The bean then enters the Ready state and is ready to consume messages.

When a message arrives for the bean, the container invokes the onMessage() method of one of the available instances, passing a Message object in argument. Message s can be consumed and processed concurrently by using multiple instances of the same type.

The container invokes ejbRemove() on the bean instance when it no longer needs the instance. The bean instance can perform clean up operations here.

The lifetime of an MDB instance is controlled by the container. Only two states exist: Does not exist and Ready , as illustrated in the following figure:



The life of an MDB instance starts when the container invokes newInstance() on the MDB class to create a new instance. Next, the container calls setMessageDrivenContext() followed by ejbCreate() on the instance. The bean then enters the Ready state and is ready to consume messages.

When a message arrives for the bean, the container invokes the onMessage() method of one of the available instances, passing a Message object in argument. Message s can be consumed and processed concurrently by using multiple instances of the same type.

The container invokes ejbRemove() on the bean instance when it no longer needs the instance. The bean instance can perform clean up operations here. Source: CoolInterview.com

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