Unidirection Mana-TO-Many - Merge doestn work - NO Cascade

shailesh.mangal · **Posted:** Mon Oct 29, 2007 3:52 pm

I have a unidirectional many-to-many relation (with implicit table). I dont want to impact the other side of object (but want to create the mapping), hence I am not using any cascading.
In such scenario, saveUpdate works fine but merge doesnt. And for various reasons, merge is desirable over saveUpdate()

Entity code

Code:

@Entity
@Table(name = "tcr_catalog_tree")
public class TCRCatalogTree implements java.io.Serializable {
@ManyToMany(fetch = FetchType.EAGER)

@JoinTable(name = "tcr_catalog_tree_user", joinColumns = { @JoinColumn(name = "tcr_catalog_tree_id") }, inverseJoinColumns = { @JoinColumn(name = "user_id",insertable = true, updatable=true) })
   private Set<User> assignedUsers = new HashSet<User>(0);

}

daiv · **Joined:** Tue Aug 07, 2007 6:18 am **Posts:** 3

Hi,

I had a similar problem but I found a workaround (not beautiful but still) like this:

public void setAssignedUsers (Set<User> users) {
if( this.assignedUsers == null) ;
this.assignedUsers = new HashSet<User>();
}
this.assignedUsers .clear();
this.assignedUsers .addAll(children);
}

My problem is fully described at:"Collection update (merge) problem"

Please, let me know if that fixed your problem.

Regards
/ daiv

shailesh.mangal · **Posted:** Tue Oct 30, 2007 12:10 pm

No, it didn't, Here is my work around. I created a specific method to update the Many-To-Many collection.

Code:

- Retrieve the object from db
- copied the collection (much like you suggested)
- Call getHibernateTemplate().[b]saveOrUpdate[/b](objectTobeSave);

Crux is - SaveOrUpdate is will always to work. In may not be possible in all cases to explicitly save the collection. It worked in our case.

-Shailesh