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Hibernate inserts duplicates into @OneToMany collection
Description
Consider following entities (getters and setters are omitted for brevity):
@Entity
public class Parent
{
@Id
@GeneratedValue
private int id;
@OneToMany(mappedBy="parent")
private List<Child> children = new LinkedList<Child>();
}
@Entity
public class Child
{
@Id
@GeneratedValue
private int id;
@ManyToOne
private Parent parent;
}
Now consider following code snippet, which persists one parent and one child entity and then prints the children of the parent.
// persist parent entity in a transaction
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
Parent parent = new Parent();
em.persist(parent);
int id = parent.getId();
em.getTransaction().commit();
em.close();
// relate and persist child entity in a new transaction
em = emf.createEntityManager();
em.getTransaction().begin();
parent = em.find(Parent.class, id);
// *: parent.getChildren().size();
Child child = new Child();
child.setParent(parent);
parent.getChildren().add(child);
em.persist(child);
System.out.println(parent.getChildren()); // -> [Child@36bf7916, Child@36bf7916]
em.getTransaction().commit();
em.close();
The child entity is wrongly being inserted twice into the list of children of the parent entity.
When doing one of the following, the code works fine (no duplicate entries in the list):
remove the mappedBy attribute in the parent entity
perform some read operation on the list of children (e.g. uncomment line marked by *)
Also, when testing against another persistence provider, the code works as expected (no duplicates).
Take a look at axtavt's answer to my post on Stack Overflow. He seems to know why this problem occurrs.
I have attached a simple JUnit test for this issue.
I think what you are saying is correct, however, I don't want to take the responsibility of closing other people's tickets. Yes, to me it seems like they are fixed, however it would be great if you could add the provided test-cases to the master branch (I tested them and they are green) before closing the tickets. Both, this one and HHH7404 seems to me are OK. I will create a new ticket now for my case.
Consider following entities (getters and setters are omitted for brevity):
@Entity public class Parent { @Id @GeneratedValue private int id; @OneToMany(mappedBy="parent") private List<Child> children = new LinkedList<Child>(); } @Entity public class Child { @Id @GeneratedValue private int id; @ManyToOne private Parent parent; }Now consider following code snippet, which persists one parent and one child entity and then prints the children of the parent.
// persist parent entity in a transaction EntityManager em = emf.createEntityManager(); em.getTransaction().begin(); Parent parent = new Parent(); em.persist(parent); int id = parent.getId(); em.getTransaction().commit(); em.close(); // relate and persist child entity in a new transaction em = emf.createEntityManager(); em.getTransaction().begin(); parent = em.find(Parent.class, id); // *: parent.getChildren().size(); Child child = new Child(); child.setParent(parent); parent.getChildren().add(child); em.persist(child); System.out.println(parent.getChildren()); // -> [Child@36bf7916, Child@36bf7916] em.getTransaction().commit(); em.close();The child entity is wrongly being inserted twice into the list of children of the parent entity.
When doing one of the following, the code works fine (no duplicate entries in the list):
remove the mappedBy attribute in the parent entity
perform some read operation on the list of children (e.g. uncomment line marked by *)
Also, when testing against another persistence provider, the code works as expected (no duplicates).
Take a look at axtavt's answer to my post on Stack Overflow. He seems to know why this problem occurrs.
I have attached a simple JUnit test for this issue.