How do you retrieve nested Sets?

Question

Is there an annotation I'm missing or is this a limitation to hibernate retrieval?

Entities:

class A {
   Long id;
   Set<B> b;

   @ManyToMany(fetch = FetchType.EAGER)
   @JoinTable(name = "A_B", joinColumns = @JoinColumn(name = "A_ID"), inverseJoinColumns = @JoinColumn(name = "B_ID")
   public Set<B> getBs() {
      return b;
   }

}

class B {
   Long id;
   Set<C> c;

   @ManyToMany(fetch = FetchType.EAGER)
   @JoinTable(name = "B_C", joinColumns = @JoinColumn(name = "B_ID"), inverseJoinColumns = @JoinColumn(name = "C_ID")
   public Set<C> getCs() {
      return C;
   }

}

DAOs:

class ADaoImpl {    
   public A load(Long id) {
      return new A((A) session.load(A.class, id);
   }
}

When I attempt to load an A, I get a

Caused by: java.lang.NullPointerException
at org.hibernate.engine.internal.StatefulPersistenceContext.getLoadedCollectionOwnerOrNull(StatefulPersistenceContext.java:853)

also please post the full stack trace (at least up to your own code). — yair, Jul 11 '13 at 21:34
Anyway it looks like Hibernate bug to me. I searched their bug DB but nothing with NPE in `StatefulPersistenceContext.java:853`. You could file a bug then. — yair, Jul 11 '13 at 21:51

score 8 · Answer 1 · answered Jan 18 '16 at 20:27

8

I had an issue very similar to this were i had nested sets, and the hashCode methods for each showed up in the stack trace. In the hashCode methods, they referred to each other, so I removed the reference to each object in the hashcode methods, and I no longer got this exceptions

answered Jan 18 '16 at 20:27

Andrew

81
1
2

There's Set in my class too and resolved same Exception by removing the reference each other in HashCode and Equals. – Junjie Feb 24 '16 at 03:18
what did you replace it with? – user_mda Jul 05 '17 at 15:50
2

Thank you so much, I had a `@Data` from lombok and it was generating my `hashCode` method using all the properties. I just added `@EqualsAndHashCode(exclude={"mySet"})` and it worked ! – tehCivilian Oct 24 '17 at 16:27

agodinhost · Answer 2 · 2013-07-12T18:55:24.770

1

I think it is not the complete exception right?

Where is the setter in class A? The b collection in class A is friendly scoped then hibernate will not be able to write/inject it's value. The same goes for the C collection in class B.

Please, copy your hibernate.xml and any other configuration class here. The hibernate/java version are important too.

edited Jul 12 '13 at 18:55

answered Jul 06 '13 at 00:59

agodinhost

381
4
16

This is the right exception. And you can assume that the DAOs are working correctly otherwise and have all necessary getter and setter methods – stackoverflow Jul 08 '13 at 11:30
If it only were the lack of an appropriate setter, Hibernate wouldn't throw NPE... – yair Jul 11 '13 at 21:32
I don't know why are you saying that, but if it's true, it would still be Hibernate bug. (unless Hibernate documents this behavior - which it probably doesn't). – yair Jul 14 '13 at 22:27

How do you retrieve nested Sets?

2 Answers2

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