JSF Controller, Service and DAO

Question

I'm trying to get used to how JSF works with regards to accessing data (coming from a spring background)

I'm creating a simple example that maintains a list of users, I have something like

<h:dataTable value="#{userListController.userList}" var="u">
    <h:column>#{u.userId}</h:column>
    <h:column>#{u.userName}</h:column>
</h:dataTable>

Then the "controller" has something like

@Named(value = "userListController")
@SessionScoped
public class UserListController {
    @EJB
    private UserListService userListService;

    private List<User> userList;

    public List<User> getUserList() {
        userList = userListService.getUsers();
        return userList;
    }
}

And the "service" (although it seems more like a DAO) has

public class UserListService {

    @PersistenceContext
    private EntityManager em;

    public List<User> getUsers() {
        Query query = em.createQuery("SELECT u from User as u");
        return query.getResultList();
    }
}

Is this the correct way of doing things? Is my terminology right? The "service" feels more like a DAO? And the controller feels like it's doing some of the job of the service.

Answer 1

It is a DAO, well actually a repository but don't worry about that difference too much, as it is accessing the database using the persistence context.

You should create a Service class, that wraps that method and is where the transactions are invoked.

Sometimes the service classes feel unnecessary, but when you have a service method that calls many DAO methods, their use is more warranted.

I normally end up just creating the service, even if it does feel unnecessary, to ensure the patterns stay the same and the DAO is never injected directly.

This adds an extra layer of abstraction making future refactoring more flexible.