Issue #840: Super class' field access fails

I have a base class:

public abstract class HotObject extends BaseObject {

  private Integer activity;

  protected HotObject() {
    activity = 1;
  }

  public Integer getActivity() {
    return activity;
  }

  public void setActivity(Integer activity) {
    this.activity = activity;
  }

  public void increaseActivity() {
    activity += 1;
  }

  protected abstract Integer getDecrease();

  public Boolean decreaseActivity() {
    Integer adaptedDecrease;
    if (activity < 50) {
      adaptedDecrease = getDecrease();
    } else if (activity < 100) {
      adaptedDecrease = getDecrease() + 5;
    } else {
      adaptedDecrease = getDecrease() + 10;
    }
    activity = activity - ((activity * adaptedDecrease) / 100) - 1;
    return activity < 2;
  }
}

And I have an inherited class:

@Entity
public class HotTag extends HotObject implements Serializable {

  private static final Integer decrease = 20; // percent
  //
  @Id
  private String name;

  public HotTag() {
  }

  public HotTag(String name) {
    this.name = name;
  }

  public String getName() {
    return name;
  }

  @Override
  protected Integer getDecrease() {
    return decrease;
  }
}

Now, when issuing the following query:

TypedQuery<HotTag> query = em.createQuery("SELECT t FROM HotTag t ORDER BY t.activity DESC", HotTag.class);

I get the exception (in objectdb 2.4.1):

com.objectdb.o.UserException: Field 'activity' is not found in type 'net.pocketservices.athene.objects.persistent.HotTag'

This can only be resolved by changing

private Integer activity;

to

public Integer activity;

in the super class. This looks like a bug to me. Normally, private access is not an issue with objectdb. I do queries on private fields all the time... So, when querying a private inherited field, I would expect this to work as well. Or is this according to the JPA spec? Then forgive me asking a stupid question.. :)

Thanks for insight!

Best, Benjamin

Please check the following test case that works:

import javax.persistence.*;

public class T840 {

    public static void main(String[] args) {
        EntityManagerFactory emf =
            Persistence.createEntityManagerFactory(
                "objectdb:d:\\temp\\test.tmp;drop");
        EntityManager em = emf.createEntityManager();

        em.getTransaction().begin();
        em.persist(new B());
        em.getTransaction().commit();
       
        em.createQuery("SELECT b FROM B b ORDER BY b.x DESC").getResultList();

        em.close();
        emf.close();
    }

    @Entity
    public abstract static class A {
        private Integer x;
    }
   
    @Entity
    public static class B extends A {
    }
}

Try to change it to reproduce the error message that you got.

In general, you should follow the posting instructions and post a test case to demonstrate an issue.

Thank you for your quick reply. One thing that I realize immediately is that you defined the base class to be an @Entity as well. Something I cannot do, as the primary key is only defined by the inherited class. So I left out the @Entity annotation in the base class.

Best, Benjamin

Hm.. maybe I was fooled by NetBeans. It is complaining about the missing id field in the base class. But the code compiles nevertheless and works also. So this was the problem: The missing @Entity annotation in the base class. Seems NetBeans has a bug here? Or is there a JPA annotation available to tell that the id field is only added in inherited classes?

If the base class is not an entity then its fields are not persistent and the error message is right.

Actually, ObjectDB should be fixed to produce a similar error also when the inherited field is public.

To avoid the NetBeans error - try annotating the base abstract class as @MappedSuperclass (instead of as @Entity).

Screenshot attached with the NetBeans indication that the code would be wrong.

Thanks so much! Problem solved!