I work on an web site project and I use hibernate with others technologies as EJB, plain JavaBeans and a RDBMS. I use also the DAO pattern. With so many technologies, i don't know excatly wich is the best approach. The problem is that i dont' know how to use the DAO pattern with hibernate, EJB and plain JavaBeans.
Can you help me to understand the role of each component and as possible can you give me an exemple that will make me understand .

Second, is it essential to use EJB in such a project ? ( can you give me some explanations )

Thanks

This would be the scope of several books!

Although christian is right, there is too much to tell in response to these questions, I would say the short answer to your question:

"Second, is it essential to use EJB in such a project ?"

Is no.

If you can get away with it, avoid the use of EJBs. There are certain situations where they are very useful, but if your intent is to craft a persistance layer in a straightforward N-tier web application, then go with straight Hibernate. If you are concerned about tight coupling with Hibernate, apply the DAO pattern to hide the implementation details..

those are not questions: they are existential problems!! ;-) just kidding!


I began developing webapps with java about 3 years ago. I started using EJB's back then and my impression now is that they are somewhat an overkill for most webapps today. With and ORM like hibernate (which performs well and is relatively light) IMHO don't see (for most cases) why you should use Entity EJB's.

As for session EJB's, I have the impression that they are more widely accepted, but EJB's have a steep learning curve and I think its easier to missuse them than actually use them properly.

My general suggestions are:

use MVC pattern (a framework like struts helps a lot here).

KISS (Keep it simple), the fewer the techonologies you mix the better
Besides, you're problably part of a team, so it helps the collaboration effort.

Maybe this would help a bit (from the old hibernate forums):

http://sourceforge.net/forum/forum.php? ... _id=128638

You can abstract the backend from the front using an API. I prefer to use the Command pattern which allows a local Command processor to be used in a servlet only senario or it can be an SLSB Command processor. It is all hidden by the API so I can switch it in and out as required. For example, one situation that the remote call may not be desirable is during the test suite execution. This means I don't have to have a container running to execute the tests.