13.4. Controller objects

The class Controller and its subclasses (EntityController, HibernateEntityController and BusinessProcessController) are an optional part of the Seam Application Framework. These classes provide a convenient method to access frequently-used built-in components and component methods. They save keystrokes, and provide an excellent foothold for new users to explore the rich functionality built into Seam.
For example, RegisterAction (from the Seam registration example) looks like this: 
@Stateless 
@Name("register") 
public class RegisterAction extends EntityController implements Register { 
  @In private User user; 
  public String register() { 
    List existing = createQuery("select u.username from 
                                 User u where u.username=:username").
                                 setParameter("username", 
                                 user.getUsername()).getResultList(); 
    if ( existing.size()==0 ) { 
      persist(user); 
      info("Registered new user #{user.username}"); 
      return "/registered.jspx"; 
    } else { 
      addFacesMessage("User #{user.username} already exists"); 
      return null; 
    } 
  } 
}