Session Bean Interface

1
Session Bean Interface

• The SessionBean Interface is used to set
• public interface SessionBean
• ejbActivate()
• ejbPassivate()
• ejbRemove()
• setSessionContext( SessionContext )

2
Session Bean Methods

• ejbActivate()
• This method is called when the instance gets
  activated from its passive state
• The instance should acquire any resource that it
  has released earlier in the ejbPassivate()
  method.

3
Session Bean Methods (Cont)

• ejbPassivate()
• This method is called when the instance enters a
  passive state and should release any resources
  that it can re-acquire later in the ejbActivate()
  method.
• After completion, the instance must be in a state
  that allows the container to use the Java
  Serialization protocol to externalize and store
  away the instance's state.
• This method is called with no transaction
  context.

4
Session Bean Methods (Cont)

• ejbRemove()
• A container invokes this method before it ends
  the life of the session object.
• This happens because the client invoked a remove
  operation or the container terminated it due to a
  timeout.

5
Session Bean Methods (Cont)

• setSessionContext( SessionContext )
• Set the associated session context. The container
  calls this method after the instance creation.
• The EJB instance should store the reference to
  the SessionContext in an instance variable.
• This method is called with no transaction
  context.

6
Exceptions Thrown

• EJBException - Thrown by the method to indicate a
  failure caused by a system-level error.
• RemoteException - This exception is defined in
  the method signature to provide backward
  compatibility for applications written for the
  EJB 1.0 specification. Should not use with beans
  written with the EJB 2.0 or later standards.

7
Clients of Session Bean

• Clients may either be remote or local
• Remote clients
• Location independent
• Can access session bean in EJB container from any
  RMI/IIOP compliant application

8
Clients of Session Bean (Cont.)

• Local Clients
• Access session bean with the local and local home
  interfaces
• Allows objects to be passed by reference
• Local clients must lie in the same JVM as the
  session bean it interfaces with

9
Clients of Session Bean (Cont.)

• Both Local and Remote home interfaces provide an
  interface to the client
• Neither access the session bean directly
• They use a component interface to the session
  bean.
• Instances of remote interfaces are called
  EJBObjects.
• Instances of local are called EJBLocalObjects.

10
Creating a Remote Interface

• Remote interfaces extend javax.ejb.EJBObject
• The bean writer provides the interface and the
  container implements it
• It provides the clients view of a session bean
  and defines any business methods that the client
  can call
• The business methods must throw at minimum the
  same exceptions as in the bean class

11
Remote Interface Methods

• EJBHome getEJBHome()
• Returns a reference to the home interface
• Handle getHandle()
• Returns a handle which can be used later to
  retrieve a reference to the EJB Object
• Object getPrimaryKey()
• Not to be used with session beans.

12
Remote Interface Methods (Cont.)

• boolean isIdentical(EJBObject obj )
• Tests whether the passed EJB Object is identical
  to the invoked EJB object.
• void remove()
• Removes a session bean object.

13
Home Interface Methods

• create()
• For every ejbCreate method in the bean class the
  home Interface must contain a corresponding
  create method
• getEJBMetaData()
• Returns an EJBMetaData interface of an EJB which
  enables the client to retrieve information about
  the enterprise bean.

14
Home Interface (Cont.)

• getHomeHandle()
• Retrieves the handle of the home object.
• May allow the client to use a remote home
  interface in the future, even though he does not
  know the JNDI name of the remote home Interface
• remove( Handle h)
• Removes the EJBObject identified with the handle
  h
• remove( Object primaryKey)
• Should not be used with SessionBeans

15
SessionBean Class

• It implements the SessionBean interface.
• The class is defined as public.
• The class cannot be defined as abstract or final.
• It implements one or more ejbCreate methods.
• It implements the business methods.
• It contains a public constructor with no
  parameters.
• It must not define the finalize method.

16
Session Bean Class Methods

• ejbCreate()
• Used to initialize the bean
• Must have
• Public access control modifier
• Return type of void
• RMI-Compliant arguments
• Not have static or final modifier
• Called when the user calls the create method of
  the home interface
• Business Methods

17
Session Bean Class Methods(Cont)

• Business Method signatures may not contain
• The method name must not conflict with one
  defined by the EJB architecture. For example, you
  cannot call a business method ejbCreate or
  ejbActivate.
• The access control modifier must be public.
• The arguments and return types must be legal
  types for Java RMI.
• The modifier must not be static or final.

18
Generated Classes

• Home stub
• Home tie
• The interface between the home stub and the Home
  Object
• Home Object
• Connects the home tie to the home life cycle
  methods

19
Generated Classes (Cont)

• Remote stub
• Remote tie
• Interface between the remote stub and the remote
  object
• Remote object
• Connects the remote tie to the business class
  code.

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