Types of Enterprise Java Beans:-
There are 3 types of enterprise bean in java as follows-
1- Session Beans:
A session bean encapsulates business logic that can be invoked programmatically by a client over local, remote, or web service client views. A session bean is not persistent, means its data is not saved to a database. EJB Session Beans has three types as below:
a .Stateful Session Bean:
In stateful session bean, the state of an object consists of the values of its instance variables. In a stateful session bean, the instance variables represent the state of a unique client / bean session.
b .Stateless Session Bean:
In EJB stateless session bean conversational state is not maintained with client. When a client invokes the methods of a stateless bean, the beanís instance variables may contain a state specific to that client but only for the duration of the invocation.
c .Single tone Session Bean:
A singleton session bean is instantiated once per application and exists for the whole lifecycle of the java application. A single enterprise bean instance is shared across all the applications clients and it is concurrently accessed by clients
2- Message Driven Bean (MDB):
Message Driven Beans ( MDBs ) also known as Message Beans. Message Driven Beans are business objects whose execution is triggered by messages instead of by method calls.
3 Entity Bean:
It encapsulates the state that can be persisted in the database. It is deprecated. Now, it is replaced with JPA (Java Persistent API).