93. EJB Drill 3

Can you control when passivation occurs? The developer, according to the specification, cannot directly control when passivation occurs. Although for Stateful Session Beans, the container cannot passivate an instance that is inside a transaction. So using transactions can be a a strategy to control passivation. The ejbPassivate() method is called during passivation, so the developer [...]

92. EJB Drill Two

What is the differnece between EJB and Java BeansExplain Local InterfacesWhat is EJB ContainerWhat is in-memory replicationWhat is ripple effectWhat’s new in the EJB 2.0 SpecificationWhat is the difference between a Coarse Grained Entiry bean and Fine Grained Entity Bean.What are transaction isolation levels in EJBWhat is the software architectury of EJBs.Waht is the need [...]

91. EJB Short Drill – One

What are the differnt kids of EJBs Stateless session bean- An instance of these non-persistent EJBs provides a service without storing an interaction or conversation state between methods. Any instance can be used for any client.Stateful session bean- An instance of these non-persistent EJBs maintains state across methods and transactions. Each instance is associated with [...]

90. What is JNDI

The Java Naming and Directory Interface (JNDI) is an application programming interface (API) for accessing different kinds of naming and directory services. JNDI is not specific to a particular naming or directory service, it can be used to access many different kinds of systems including file systems; distributed objects systems like CORBA, Java RMI, and [...]

89. What’s the difference between servlet/JSP session and EJB Session

A session in a Servlet, is maintained by the Servlet Container through the HttpSession object, that is acquired through the request object. You cannot really instantiate a new HttpSession object, and it doesn’t contains any business logic, but is more of a place where to store objects. A session in EJB is maintained using the [...]

88. Compare stateless and statefull session bean

Stateless Session Beans Stateful Sessions Beans Are pooled in memory, to save the overhead of creating a bean every time one is needed. WebLogic Server uses a bean instance when needed and puts it back in the pool when the work is complete. Stateless sessions beans provide faster performance than stateful beans. Each client creates [...]

87. How to choose between stateless and statefull beans

Stateless session beans are a good choice if your application does not need to maintain state for a particular client between business method calls. WebLogic Server is multi-threaded, servicing multiple clients simultaneously. With stateless session beans, the EJB container is free to use any available, pooled bean instance to service a client request, rather than [...]

What is the difference between CMP and BMP

Short answer: with bean-managed persistence, you can optimize your queries and improve performance over the generalized container-managed heuristics. But container-managed persistence is very convenient, and vendors will be working to improve its performance as time goes on.] There is of course a difference as many CMPs use O-R mapping using metadata, which is slower than [...]