parent-child relationship problem

natereed · **Joined:** Wed Dec 20, 2006 12:35 pm **Posts:** 1

I have a question about object semantics and implementing parent-child relationships in Hibernate. Parent has a list of children, and Child has a reference to its parent.

The problem is: the Parent's collection of children does not actually contain the Child object; it contains a copy. When I modify the Child, the same Child in Parent's collection of children does not get updated. This defies my expectations about how Hibernate should work. Is it possible I have the mappings incorrect?

Example:

Code:

Child child = childDao.findById(id);
child.setProperty(value);
....
childDao.saveChild(child); // save child

// Get all the parent's children
List children = parent.getChildren();

The List 'children' still contains the version of child before the modification above.

Here is the mapping in Parent:

Code:

   /**
    * @hibernate.bag name="children" lazy="false" cascade="all"
    * @hibernate.collection-key column="parent_id"
    * @hibernate.collection-one-to-many
class="com.myproject.model.Child"
    */
   public List getChildren() {
       return this.children;
   }

   public void setChildren(List children) {
       this.children = children;
   }

In Child:

Code:

   /**
    * @hibernate.property column="parent_id"
    * not-null="true"
    */
   public int getParentId() {
       return this.parentId;
   }

   public void setParentId(int parentId) {
       this.parentId = parentId;
   }

I have tried with and without the following mapping in Child:

Code:

  /**
    * @hibernate.many-to-one class="com.myproject.model.Parent"
cascade="none"
    * column="parent_id" update="false" insert="false"
    */
   public Parent getParent() {
       return this.parent;
   }

   public void setParent(Parent parent) {
       this.parent = parent;
   }

Any ideas what's wrong? Perhaps I have missed something fundamental about the way Hibernate works? I would expect Hibernate queries for the same database objects to yield equal (==) object references; is this not the case?

Thanks,
Nate

kochcp · **Posted:** Wed Dec 20, 2006 4:12 pm

look in the logs. see if the updated child is getting saved when you call save. better yet, try to update it and see if that is getting called before that load command runs.