Sam P

• May 3rd, 2005

 

From a logical point of view, a Servlet/JSP session is similar to an EJB session. Using a session, in fact, a client can connect to a server and maintain his state. 
But, is important to understand, that the session is maintained in different ways and, in theory, for different scopes. 
 
A session in a Servlet, is maintained by the Servlet Container through the HttpSession object, that is acquired through the request object. You cannot really instantiate a new HttpSession object, and it does not contains any business logic, but is more of a place where to store objects. 
 
A session in EJB is maintained using the SessionBeans. You design beans that can contain business logic, and that can be used by the clients. You have two different session beans: Stateful and Stateless. The first one is somehow connected with a single client. It maintains the state for that client, can be used only by that client and when the client "dies" then the session bean is "lost". 
 
A Stateless Session Bean does not maintain any state and there is no guarantee that the same client will use the same stateless bean, even for two calls one after the other. The lifecycle of a Stateless Session EJB is slightly different from the one of a Stateful Session EJB. Is EJB Containers responsability to take care of knowing exactly how to track each session and redirect the request from a client to the correct instance of a Session Bean. The way this is done is vendor dependant, and is part of the contract.

J. P. Naidu

• Jul 28th, 2005

 

Session Bean comes with the implicit services where as HHTPSession does not.  
 
Session Bean can be web based or can be stand alone where the other can only be web based. 
 
Session Bean can be used for multiple operation for a single HTTP request but the other cannot.