[appengine-java] owned one to many relationship problem

[ylmz]

Hi every body. I have a problem with my model and I cannot figure out
what the problem is. So any help would be appreciated. to explain the
problem I wrote some sample code:
Here is my model:

Class A has one to many relationship with B
Class B has one to many relationship with C

@PersistenceCapable(identityType = IdentityType.APPLICATION)
class A {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    public Key key;
    @Persistent(mappedBy = "a")
    @Element(dependent = "true")
    public List<B> bList = new LinkedList<B>();
}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
class B {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    public Key key;
    @Persistent(mappedBy = "b")
    @Element(dependent = "true")
    public List<C> cList = new LinkedList<C>();
    @Persistent
    public A a;
}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
class C {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    public Key key;
    @Persistent
    public B b;
}


in my code;
1) I created class A B and C
2) I persisted A
3) I retrieved A from DB and add B to its list.
4) I retrieved B from DB and add C to its list.

but in step 4, I cannot retrieve B from DB, instead I get following
exception
javax.jdo.JDOObjectNotFoundException: Could not retrieve entity of
kind B with key B(4).

Code :

PersistenceManager pm = PMF.get().getPersistenceManager();

//1)Create A,B,C
A a = new A();
B b = new B();
C c = new C();

//2)Persist A
pm.currentTransaction().begin();
try {
   pm.makePersistent(a);
   pm.currentTransaction().commit();
} finally {
   if(pm.currentTransaction().isActive())
      pm.currentTransaction().rollback();
}

//3)get A from DB and add B to its list
pm.currentTransaction().begin();
try {
  A newA = pm.getObjectById(A.class,a.key.getId());
  newA.bList.add(b);
  pm.currentTransaction().commit();
} finally {
   if(pm.currentTransaction().isActive())
      pm.currentTransaction().rollback();
}

//4) get B from DB and add C to its list
pm.currentTransaction().begin();
try {
   /********************Error*********************/
   B newB = pm.getObjectById(B.class,b.key.getId());//we cannot
retrieve this object. why?
   newB.cList.add(c);
   pm.currentTransaction().commit();
} finally {
   if(pm.currentTransaction().isActive())
      pm.currentTransaction().rollback();
}

Please note that I am not sure that this is how I suppose to implement
owned one to many relationship I got that implementation from
following post

http://groups.google.com/group/google-appengine-java/browse_thread/thread/28d9c3b99df25e43/b43702a150c5aa1b?lnk=gst&q=owned+one+to+many+getObjectById#b43702a150c5aa1b

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