Immutable list for Association causes Exception on Merge

keenan · **Joined:** Mon Jan 09, 2006 3:05 pm **Posts:** 24

Hibernate version:
* Hibernate Core 3.2.0.CR2
* Hibernate Annotation 3.2.0.CR1
* Hibernate Entity Manager 3.2.0.CR1

Mapping documents:

Annotated entity classes Parent and Child, in a Many to Many bidirectional relationship with Child being the owning side. These are as vanilla as you can get, but code available on request.

Code between emf.createEntityManager() and em.close():

Code:

        em.getTransaction().begin();       
        Parent p = new Parent();
        em.persist(p);        
        Child c = new Child(Arrays.asList(p));
        em.persist(c);               
        em.getTransaction().commit();   
     
        em.merge(c);

Description of Problem
In a Java 5 SE environment, which runs in an extended persistence context, executing the above code causes an exception when JPA/hibernate tries to modify the immutable list returned by Arrays.asList(). The standard says:

Quote:

If X is a managed entity, it is ignored by the merge operation

which obviously isn't happening.

Obviously, the merge above isn't necessary since it is all within the same persistence context, but in general what restrictions, if any, are put on the POJOs that you hand to the entity manager?

Full stack trace of any exception that occurs:

Code:

java.lang.UnsupportedOperationException
   at java.util.AbstractList.remove(Unknown Source)
   at java.util.AbstractList$Itr.remove(Unknown Source)
   at java.util.AbstractList.removeRange(Unknown Source)
   at java.util.AbstractList.clear(Unknown Source)
   at org.hibernate.collection.PersistentBag.clear(PersistentBag.java:344)
   at org.hibernate.type.CollectionType.replaceElements(CollectionType.java:404)
   at org.hibernate.type.CollectionType.replace(CollectionType.java:449)
   at org.hibernate.type.TypeFactory.replace(TypeFactory.java:431)
   at org.hibernate.event.def.DefaultMergeEventListener.copyValues(DefaultMergeEventListener.java:282)
   at org.hibernate.event.def.DefaultMergeEventListener.entityIsPersistent(DefaultMergeEventListener.java:132)
   at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:105)
   at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:51)
   at org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:679)
   at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:663)
   at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:667)
   at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:201)
   at com.acompany.persistence.TestJPA.testMerge(TestJPA.java:60)

emmanuel · **Posted:** Sun Jul 09, 2006 7:05 am

I'm having hard time understanding your mapping, can you provide PArent and Child mapping?

keenan · **Joined:** Mon Jan 09, 2006 3:05 pm **Posts:** 24

Welcome back Emmanuel. We missed you!

Following are the parent child classes with embedded mapping annotations. They are straightforward. I think the real problem is the Immutable list holding the parents.

Parent.java

Code:

@Entity
public class Parent {
    
    private long id;
    private Collection<Child> children;

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    public long getID() {
        return id;
    }
    public void setID(long id) {
        this.id = id;
    }

    @ManyToMany(mappedBy="parents")
    public Collection<Child> getChildren() {
        return children;
    }
    public void setChildren(Collection<Child> kids) {
        this.children = kids;        
    }
} // Parent

Child.java

Code:

@Entity
public  class Child {
    
    private long id;
    private Collection<Parent> parents;
    
    /**
     * Satisfy the JavaBean contract
     *
     */
    public Child() {
    }
    
    public Child(Collection<Parent> parents) {
        setParents(parents);
    }
    
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    
    @ManyToMany()
    public Collection<Parent> getParents() {
        return parents;
    }
    public void setParents(Collection<Parent> parents) {        
        this.parents = parents;
    }

} // Child

emmanuel · **Posted:** Sun Jul 16, 2006 12:23 pm

Year, I know I was (and still am) very busy working. But I'll try to come every now and then here. I like to get feedbacks from you guys.

http://opensource.atlassian.com/projects/hibernate/browse/HHH-1914

Not sure this will be fixed though, because your use case is really weird. If you don't want the colelction to be changed, then mark the columns as updatable=false

keenan · **Joined:** Mon Jan 09, 2006 3:05 pm **Posts:** 24

It is a strange use case, and probably not worth fixing unless someone can come up with a better reason.
--keenan