Null pointer when accessing entity manager in abstract class

[mhiggins.matt.smartdestinations.com]

I have the following situation. I have a DAO (service) that extends an abstract service that has the basic features for saving and updating entities in which I grab an entity manager and try to do work. I can use the entity manager fine in the concrete class but not in the abstract class where I get a null pointer. Here is the relevant code and stack trace. I hope this is not to much info.

Using seam 2.1.2

Here is the Service (DAO)
@Name("venueService")
public class VenueService extends AbstractEntityService<Venue> {
     
     @SuppressWarnings("unchecked")
     public List<Venue> findByCompanyId(Long companyId){
          return getEntityManager().createQuery("from Venue where company.id = :id").setParameter("id",companyId).getResultList();
     }

}

Note where I get the entity manager.. I have tried using @In with the same result.
public abstract class AbstractEntityService<T> implements EntityService<T> {
     
     @Logger Log log;
     
     
     private Class<T> persistentClass;
     
     public T findById(Long id){
          return getEntityManager().find(persistentClass, id);
     }
   public EntityManager getEntityManager(){
         
         return (EntityManager) Component.getInstance("entityManager");
    }
   
}

@Path("/user/{username}/{password}")
@Name("userResource")
public class UserResource {

     @Logger
     Log log;
     
     @In(create=true)
     UserService userService;
     
     @In(create = true)
     VenueService venueService;

@GET
     @Path("/favorite/{favoriteId}")
     @Produces("application/xml")
     public VenueDto getFavorite(@PathParam("username") String username, @PathParam("password") String password, @PathParam("favoriteId") Long favoriteId){
          User user = userService.findUserByUnameOrEmail(username, username);
          VenueDto venueDto = new VenueDto();
          if(userService.validatePassword(user, password)){
               Venue venue = venueService.findById(favoriteId);
               if(venue != null){
                    venueDto = venueDtoBuilder.buildDto(venue);
               }
          }
          return venueDto;
     }
     
}


java.lang.NullPointerException
     at org.hibernate.impl.SessionImpl.get(SessionImpl.java:835)
     at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:182)
     at org.jboss.seam.persistence.EntityManagerProxy.find(EntityManagerProxy.java:87)
     at com.swarm.service.AbstractEntityService.findById(AbstractEntityService.java:22)

[asookazian]

what happens if you remove the abstract keyword from your class?

public class AbstractEntityService<T> implements EntityService<T> {...}

[asookazian]

Well I just tried this and it works fine:

public abstract class TestAbstractEntityManagerFactory {
     @Logger private Log log;
     
     public EntityManager getEntityManager(){
         return (EntityManager) Component.getInstance("entityManager");
     }
     
}

@Name("myTest1")
@Scope(ScopeType.CONVERSATION)
public class TestApplicationMetaDataAction extends TestAbstractEntityManagerFactory {

    private EntityManager entityManager;

    @DataModel
    private List<ApplicationMetaData> apmdList_main;

    @Begin(join=true, flushMode=FlushModeType.MANUAL)
    @Factory("apmdList_main")
    public void getDataTable(){
          
          entityManager = super.getEntityManager();
          
          if (apmdList_addRow != null && apmdList_addRow.size() > 0)
               apmdList_addRow.clear();
          
          apmdList_main = entityManager.createQuery("from ApplicationMetaData").getResultList();
          
    }

}

I learned that you'll get a deployment exception if you add a @Name annotation to an abstract class...

Now I'm wondering if an interface can be a Seam component...???

survey says.......... no, that's illegal as well...

Caused by: java.lang.IllegalArgumentException: component class is an interface: testInterface

[mhiggins.matt.smartdestinations.com]

What you need to do is put a function in the abstract class make use of the entity manager and execute from the concrete class.

I also tried the other idea of making the abstract class concrete and I have the same problem.

[mhiggins.matt.smartdestinations.com]

I was a little hasty in that last response. To test you need to execute one of the abstract methods from another class. In the example above I execute venueService.findById(venueId) which is only on the abstract class.

And thank for responding so fast! 

[mhiggins.matt.smartdestinations.com]

I am still having an issue with this. I am hoping to get clarification on how / where the injection of the entity manager occurs. If I have an abstract class with an @In annotation it appears I can not use the injected object (in this case the enityManager) the abstract class, only in the concrete class.