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Interview :: EJB

EJB - General Questions
1) What is EJB?

EJB stands for Enterprise Java Bean. It is a server-side component to develop scalable, robust and secured enterprise applications in java.

2) What are the types of Enterprise Bean?

There are three types of enterprise bean in java.

  1. Session Bean
  2. Message Driven Bean
  3. Entity Bean
3) What is session bean?

Session Bean encapsulates business logic. It can be invoked by local, remote or web service client.

There are 3 types of session bean.

  1. Stateless Session Bean
  2. Stateful Session Bean
  3. Singleton Session Bean
4) What is stateless session bean?

A Stateless session bean is a business object that doesn't maintain the conversational state with the client.

5)

Write down the steps for the creation of stateless EJB?

  • Create a local interface.
  • The interface is to be used by the client application.
  • In case the EJB client environment is the same, use @Local annotation.
  • In case the EJB client environment is different, use @Remote annotation.
  • Create a stateful session bean.
  • To signify a stateful bean, use @Stateful annotation.
6) What is stateful session bean?

A Stateful session bean is a business object that maintains the conversational state with the client.

7) What is singleton session bean?

Singleton session bean is instantiated only once for the application. It exists for the life cycle of the application.

8) What is JMS?

Java Message Service is a messaging service to create, send and receive messages asynchronously.

9) What are the advantages of JMS?
  • Asynchronous
  • Reliable
10) What is PTP model?

In Point to Point model, one message is delivered to one receiver only. Here, Queue is used as a message-oriented middleware.

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