B2B Integration : A Practical Guide to Collaborative E-commerce

248 B2B Integration — A Practical Guide to Collaborative E-commerce
Session beans
Session beans represent behaviors associated with client sessions. A
session bean instance is typically private to a particular client connection.
It is usually not shared among multiple clients and therefore becomes a
logical extension of the client application. Interfaces are defined to
support a session bean accessing and modifying data as part of a
transaction.
SESSION BEAN PROPERTIES
• Transaction capable;
• Handles one transaction at a time;
• Accesses and updates database for the client;
• A logical extension of the client;
• Used only by client who creates it;
• Short lived — lives only as long as the client;
• Does not survive crash of client or server;
• Hides its identity (appears anonymous);
• No finder method; and
• Fields represent the state of the transient conversation with the
client.
Stateless versus stateful session beans
Session beans can be either stateful or stateless. A stateless session
bean does not maintain an internal state and has no persistence. The
state of the bean will always be the same both before and after any
method calls or transactions have occurred. Since session beans of the
same type are identical, they can be pooled to service multiple clients.
They can also be created and destroyed easily by the container, since
they hold no state.
A stateful session bean, on the other hand, maintains an internal
state that can be accessed and modified directly by the client. A stateful
bean can be accessed by only one EJB client and becomes a logical