Where (which layer) to put Entity query methods, “persist” methods etc. ?

[anders.norgaard]

Sorry, if this is slightly off topic. I am trying to get the most of my SEAM experience, but I am getting annoyed with my own inability to architect properly. So I wonder...

I have a SEAM app running on JBoss 4.2 with some JPA/Hibernate entities. And I now wonder where to put my query, persistence methods.

The default choice seems to put them in a session bean layer with injected

@PersistenceContext(...) @Inject EntityManager entityManager;

But I think I would rather have the methods on the entities themselves (like .persist() etc) maybe some static? What are the pro's/con's wrt.

   1. Testablity?
   2. Niceness?
   3. Performance?

And does anyone have links to best practices for interacting with the EntityManager etc. from methods on the Entities rather than session beans?

Best, Anders

PS Why I don't just do the DAO-kind-of-layer: In general, I think, EJB is insanely verbose and boilerplate'y, but SEAM actually helps a bit, so that is why, in my current project, the extra layer of session beans just to query and persist annoys me. I have the feeling that I could make a reasonably concise app if I could kill this layer...

[thejavafreak]

The most common usage is to place it in your Session Bean, because the idea of Seam from the beginning is to reduce layer by joining JSF managed bean and Session Bean for Action class. But some people add another DAO layer for this, but I'd prefer using Session Bean because Session Bean is a plain POJO and you can easily unit test it. So why would I need another layer for this?

[anders.norgaard]

Ah, but I do want to reduce the number of layers. And I realize that I have some session beans/SEAM objects where I could put some private query methods. But what if another bean needs the same query? Code duplication is bad, so where to put the common code (query method)?

In a stateless session bean that both SEAM objects can access?

or

On the entity object itself? (and in that case, how do I best obtain the EntityManager/Hibernate Session?)

Best
Anders