a2zinterviews

29.	What is the main advantage of EJB over CORBA with respect to CTM design?
	The problem with CORBA CTM designs was that they all had different server-side component models. In other words, if you developed a component for one vendor's CTM, you couldn't turn around and use that same component in another vendor's CTM. The component models were too different. EJB is a standard server-side component model with which one can develop business objects and expect them to work in any CTM that supports the complete EJB specification. With a standard server-side component model, customers can commit to using an EJB-compliant CTM with the knowledge that they can migrate to a better CTM, if one becomes available.
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30.	Define the Enterprise JavaBeans (EJB)?
	The Enterprise Java Beans architecture is a component architecture for the development and deployment of component-based distributed business applications. Applications written using the Enterprise Java Beans architecture is scalable, transactional, and multi-user secure. These applications may be written once and then deployed on any server platform that supports the Enterprise Java Beans specification.
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31.	Explain the term Concurrency in EJB?
	The concurrency is one of the primary services required to create an effective CTM, supported by EJB. Entity beans are shared components. Entity beans represent data in the database that is shared and needs to be accessed concurrently. Session Beans do not support concurrent access. A stateful bean is an extension of one client and only serves that client. If they are only used by the client that created them, it does not make sense to make stateful beans concurrent. Stateless session beans don't need to be concurrent because they don't maintain state that needs to be shared. EJB servers handle concurrency automatically and, therefore, a bean's methods do not have to be made thread safe.
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32.	When is bean managed persistence used?
	Bean Managed Persistence is used as an alternative to container managed persistence when the deployment tools are inadequate for mapping the bean instance's state to the database. Bean Managed Persistence is preferred by the enterprise developers for creating custom beans for their business system.
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