Friday, March 02, 2007

JAVA 認證心得 -- SCBCD (6)

Client View of an Entity

  • Javax.ejb.NoSuchEntityException is the exception thrown if a remote client attempts to access an entity bean object, which has already been removed. Maybe thrown by the bean component business methods , and by the ejbLoad() and ejbStore()

  • Entity bean allow shared access from multiple users.
  • Entity bean can expose a remote interface to serve remote clients, a local interface to serve local clients or both.
  • The remote home interface can be used to create, remove and find entity objects
  • The create<METHOD> methods in the entity bean's home interface must return the component interface type and must include javax.ejb.CreateException in their throws clause. Because the interface is the local home interface, therefore, create<METHOD> methods defined in it must not throw java.rmi.RemoteException.
  • A remote client can be in the same or different JVM as the entity bean instance. When the remote client and entity bean instance are in the same JVM even then the client accesses entity bean instance as it is remotely located.
  • Javax.ejb.HomeHandle interface must be implement by an entity bean’s home handle class.
  • A handle class for a remote component interface of an entity bean must implement the interface and the javax.ejb.Handle interface

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