Hi advance HAPPY NEW YEAR.i am new to the concept of EJB's ,actually why we need EJB and before EJB' were not there which one did the job of EJB's.and Where it excatly in MVC pattern. Thankns in advance
EJBs form the Business Layer. In the MVC pattern they are at the Model Layer. EJB is where you write all the Business Logic of your application. EJBs can be Session, Entity or Session Types, and interface with the database using DAOs(Session) or directly(Entity). Learning of EJBs is available on the internet. A very good book would be Ed Roman for beginners. [ December 27, 2005: Message edited by: Pratik Lohia ]
I'd say entity EJBs can be thought of as part of the Model or, better yet, the Persistence layer. (Unfortunately, there's no persistence explicitly in MVC.)
SLSB can be part of the Controller layer, as can SFSB.
Where to slot MDBs? No clients for those, so they weren't part of the pattern when Smalltalkers came up with it. Controllers can make use of MDBs, so you might lump them in there, but they're more properly part of asynchronous processing patterns.