CascadeType is misbehaving!

[justinmiller]

I am seeing something very weird with respect to cascading. There are really two problems. Let's say that I have classes A and B, and then a main method below that:

@Entity
@Table(name="A")
public class A {

 @Column(name="ID")
 private String id;

 @OneToMany(cascade= {CascadeType.REMOVE, CascadeType.REFRESH, CascadeType.PERSIST})
 @JoinColumn(name="PARENT_ID")
 private Collection<B> children;


 public A() {
 super();
 }

 public A(String id) {
 this.id = id;
 }

 public Collection<B> getChildren() {
 return children;
 }


 public void setChildren(Collection<B> children) {
 this.children = children;
 }

 public String getId() {
 return id;
 }

 public void setId(String id) {
 this.id = id;
 }

}

@Entity
@Table(name="B")
public class B implements Serializable {

 @Column(name="ID")
 private String id;

 @Column(name="PARENT_ID")
 private String parent;

 public B() {
 super();
 }

 public B(String id) {
 this.id = id;
 }

 public String getId() {
 return id;
 }

 public void setId(String id) {
 this.id = id;
 }

 public String getParent() {
 return parent;
 }

 public void setParent(String parent) {
 this.parent = parent;
 }

}

public class EJB3Test {

 public static void main(String[] args) {
 A a = new A(generateId());
 B b = new B(generateId());

 a.setChildren(Arrays.asLis(new B[] { b }));
 b.setParent(a.getId());

 //for argument's sake, let's just say SessionFacade is just a wrapper
 //around EntityManager.persist/merge/remove
 SessionFacade.persist(a);

 a = new A(a.getId());

 //let's say we've changed 'a' somehow, and we want those changes
 //persisted, but we WANT it's relationship to it's children
 //preserved.
 SessionFacade.merge(a);
 }
}

The first problem:
Notice how I don't have CascadeType.MERGE set on the relationship between A and it's children. Why then, when I do the merge(), will it attempt to set B.PARENT_ID to null? I would think that if it's not set to cascade on a merge, the EntityManager shouldn't even touch children. I have found however, that setting updatable=false on the JoinColumn causes the expected behavior.

The second problem is an extension of the first:
Let's take it one step further, assuming we set updatable=false, and right before we try SessionFacade.merge(a), we do this:

a.setChildren(Arrays.asList(new B[] { new B(someNewId) } ));

//then do:
SessionFacade.merge(a)

The merge now throws an exception, even though it's NOT set to cascade on merge, and children is set to updatable=false. The exception we get is an EntityNotFoundException stating that it can't find an object B with id: someNewId. Well no kidding! It's not there! I know it seems weird to NOT want to cascade, but I assure you - in my context, I simply need more control over how the children are inserted. Therefore, it makes perfect sense to have children that I do not want persisted until I explicitly do so.

I shouldn't have to grab a reference to the children, null out the field in A, and then merge all the children.

Collection<B> children = a.getChildren();
a.setChildren(null);

SessionFacade.merge(a);

for(B child : children)
 SessionFacade.merge(child);

ANY help would be greatly appreciated!!! This is driving me crazy!

[fhh]

Your ERM is completly broken:

public String getParent() {
 return parent;
 }

 public void setParent(String parent) {
 this.parent = parent;
 }

If you want a bidirectional relationship you want to return the referenced object not its id:

public A get Parent() {
 return a;
}

public setParent(A a) {
 this.a = a
}

Regards

Felix

[justinmiller]

I don't actually need the birdirectional relationship. That's why I didn't include it. I only needed the id to map the unidirectional relationship.

[fhh]

I only needed the id to map the unidirectional relationship.

No, you don't.

Regards

Felix