JSF / EJB3 avoiding lazy initialization exceptions in the view layer - jsf

Question

I have the following JSF/PrimeFaces EJB architecture:
[JSF/PrimeFaces xhtml view] --> [#ManagedBean JSF bean] --> [#Stateless EJB3 bean] --JPA--> [DB]
That is, the JSF views display entities and collections they access on their backing beans (#ManagedBean) and these collections and entities are in turn fetched by calling stateless EJB3 "facade" beans that have the EntityManager injected and access the database using JPA backed by Hibernate. The stateless EJB3 beans also provide some services but for the most part their role is to provide the Entity objects (JPA-annotated) from the database, as requested by the xhtml views that need to display them.
Now here's the thing: if my understanding is correct, the moment the Entity beans are returned by the stateless EJB3 beans, they become detached as each EJB3 bean method demarcates a transaction. It is then often the case that as the xhtml views and the JSF Managed beans navigate the graphs of the Entity objects so fetched (One-To-Many collections and such), I often get Lazy Initialization exceptions like the following:
javax.el.ELException: ... org.hibernate.LazyInitializationException: failed
to lazily initialize a collection of role: ..., no session or session was closed
The only thing that works is changing collections to be EAGER -ly loaded but that's not a pragmatic solution. What are some good patterns to use when detached JPA entity find their way to the view layer in order to avoid once and for all the lazy initialization exceptions rather than having to treat each case in an ad-hoc manner?

Answer 1

There are two ways of handling lazy associations. The first way is to initialize the entity using:
Hibernate.initialize(proxy)
or set the fetch type to EAGER which will fetch the entire entity when you load it.
The second and the more proper way (in my opinion) is to keep the entity manager as long as you keep the entities. This could be done either using a #Stateful session like this:
#Stateful
public class UserService {
#PersistenceContext(type=EXTENDED)
private EntityManager entityManager;
...... the business method
}
and keep a reference to the ejb as long as you keep the entity. More info about extended persistence context could be found here.
Other way to keep the entity manager is to use CDI modules like seam-persistence or CODI that offer a functionality to create and keep an EntityManager to conversation scope.