3.0b4 and UserCollectionType interface changes

bago · **Joined:** Wed Feb 04, 2004 4:54 am **Posts:** 25

Hibernate version:
3.0b4

In hibernate 3.0b3 I implemented my custom UserCollection by adding a new class (HibernateHQLPersistentSet) extending PersistentSet and implementing my own collection business interface and adding a new class implementing UserCollectionType (HibernateHQLSetType) defined as follow:

Code:

public class HibernateHQLSetType implements UserCollectionType {

   public PersistentCollection instantiate(SessionImplementor arg0,
         CollectionPersister arg1) throws HibernateException {
      return new HibernateHQLPersistentSet(arg0);
   }

   public PersistentCollection wrap(SessionImplementor arg0, Object arg1) {
      return new HibernateHQLPersistentSet(arg0, (Set) arg1);
   }

}

When I upgraded to hibernate 3.0b4 I found that I should implement the following methods of the UserCollectionType interface!

Code:

   /**
    * Optional operation. Does the collection contain the entity instance?
    */
   public boolean contains(Object collection, Object entity);
   /**
    * Optional operation. Return the index of the entity in the collection.
    */
   public Object indexOf(Object collection, Object entity);

What should I do if I don't want to implement the optional methods? Should I throw an UnsupportedOperationException?

Code:

   
   /**
    * Return an iterator over the elements of this collection - the passed collection
    * instance may or may not be a wrapper
    */
   public Iterator getElementsIterator(Object collection);

   /**
    * Replace the elements of a collection with the elements of another collection
    */
   public void replaceElements(
         Object original, 
         Object target, 
         CollectionPersister persister, 
         Object owner, 
         Map copyCache, 
         SessionImplementor session)
         throws HibernateException;
   
   /**
    * Instantiate an empty instance of the "underlying" collection (not a wrapper)
    */
   public Object instantiate();

Should I simply change my own HibernateHQLSetType that was only implementing UserCollectionType by extending UserCollectionType or better SetType?

bago · **Joined:** Wed Feb 04, 2004 4:54 am **Posts:** 25

I tested the "extend" solution but also extending SetType doesn't fix all the problems: there are still methods to be implemented... Why SetType doesn't need to implement this methods while a UserCollectionType does?

the replaceElements and the no-argument instantiate are not there.

Why and when this methods are called? What are they supposed to do?

gavin · **Posted:** Fri Feb 11, 2005 4:54 pm

SetType inherits them from CollectionType.

You only need to implement these methods if you plan to use unidirectional one-to-many associations with <key column=".." not-null="true"/>

bago · **Joined:** Wed Feb 04, 2004 4:54 am **Posts:** 25

gavin wrote:

SetType inherits them from CollectionType.

Then I believe there's a bug because that's not true:

UserCollectionType define:

Code:

public void replaceElements(
         Object original, 
         Object target, 
   >>>   CollectionPersister persister,      <<<
         Object owner, 
         Map copyCache, 
         SessionImplementor session)
         throws HibernateException;

CollectionType define:

Code:

public Object replaceElements(
         Object original, 
         Object target, 
         Object owner, 
         Map copyCache, 
         SessionImplementor session)
         throws HibernateException { 

some difference also apply to "public Object instantiate()".

gavin wrote:

You only need to implement these methods if you plan to use unidirectional one-to-many associations with <key column=".." not-null="true"/>

Ok, thank you for the explanation!

bago · **Joined:** Wed Feb 04, 2004 4:54 am **Posts:** 25

I see in sources that CustomCollectionType does this:

Code:

   public Object replaceElements(Object original, Object target, Object owner, Map copyCache, SessionImplementor session)
   throws HibernateException {
      CollectionPersister cp = session.getFactory().getCollectionPersister( getRole() );
      userType.replaceElements(original, target, cp, owner, copyCache, session);
      return target;
   }

I assume that I simply should add the replaceElement and call the replaceElement from "super" taking away the persister.

What about the instantiate?
I get a call to instantiate() with no arguments while my superclass (SetType) only implements instantiate(Object o)... what should be passed to that superclass method?

gavin · **Posted:** Fri Feb 11, 2005 10:08 pm

Just because the argument list is different, don't assume the semantics are different.