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 a particular
Entity bean- An instance
of these persistent EJBs represents an
object view of the data, usually rows
in a database. They have a primary key
as a unique identifier. Entity bean persistence
can be either container-managed or bean-managed.
An instance of these EJBs is integrated
with the Java Message Service (JMS) to
provide the ability for message-driven
beans to act as a standard JMS message
consumer and perform asynchronous processing
between the server and the JMS message