Hibernate self ManyToMany save problem

I have a class Node Node.java

public class WebPage implements BusinessObject {
  @Id
  private Long       id;
  @ManyToMany
  @JoinTable(name = "childnodes")
  private Set<WebPage> references;   // nodes contained by this node
}

My requirements :

1. One node can reference many nodes.
2. One node can reference it self.
3. One node can be referenced by many nodes or not.

I want to do something like this :

1. Node A -> Node B (Node A references Node B and so on)

2. Node A -> Node C

3. Node A -> Node D

4. Node B -> Node E

5. Node B -> Node C

All steps run OK except the 5th one. I have an exception : Unique index or primary key violation: How can i tell Hibernate to DO NOT try to insert Node C开发者_如何学C but instead update it !

You didn't provide the code which tries to create all entities. However, the flow would be something like,

1. Create/Retrieve all nodes required for Node B
2. Populate Node B with all those
3. Save Node B with cascade-insert

The problem was not on Hibernate behalf but on a bug in my code :\