[jboss-user] [EJB 3.0] - 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!

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