Java Stream Question and Answers

5. Which application server have you used for EJB?
  JBOSS as the application server to host EJB components.
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6. Can you explain the concept of local interfaces?
  • JAVA client calls the local stub.
  • Stub Marshal's the values in to some other form which the network understands and sends it to the skeleton.
  • Skeleton then de-marshals it back to a form which is suitable for JAVA.
  • EJB object then does object creation, connection pooling, transaction etc.
  • Once EJB object calls the bean and the bean completes its functionalities.
  • So you can easily guess from the above step that its lot of work. But this has been improved in EJB 2.0 using Local objects.
  • Local objects implement local interface rather than using remote interface. Just to have a comparison below are the steps how the local object works.
  • JAVA client calls the local object.
  • Local object does connection pooling, transactions and security.
  • It then passes calls the beans and when bean completes its work it returns the data to the Local object who then passes the same to the end client.
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7. How does the server decide which beans to passivate and activate?
  Most servers use the (LRU) Last Recently Used Time as a strategy. Which mean passivate the beans which have been called recently.
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8. What are the limitations of using local object?
  • Local object only work if you are calling beans in the same process. Second they marshal data by ref rather than by val.
  • This may speed up your performance but you need to change semantics for the same.
  • So finally it's a design and the requirements decision. If you are expecting to call beans remotely then using local object will not work.
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