<hibernate-mapping>
   <class
     name="test.hibernate.Box"
     table="box">

     <id
        name="boxID"
        column="bid"
        unsaved-value="null"
        access="field"
        type="integer">
        <generator class="native"/>
     </id>

    <version name="version" access="field" column="version" type="integer"/>

      <property
        name="boxNumber"
        column="boxNr"
        type="integer"/>
       
     <set
      name="toys"
      table="toy"
      inverse="true"
      outer-join="true"
      cascade="save-update">
      <key column="box_bid"/>
      <one-to-many class="test.hibernate.Toy"/>
    </set>
   
    <many-to-one
      name="delivery"
      column="Delivery_did"
      class="test.hibernate.Delivery"
      outer-join="true"/>
   </class>

</hibernate-mapping>

<hibernate-mapping>
   <class
     name="test.hibernate.Delivery"
     table="delivery">

     <id
        name="deliveryID"
        column="did"
        unsaved-value="null"
        access="field"
        type="integer">        
        <generator class="native"/>
     </id>

    <version name="version" access="field" column="version" type="integer"/>
   
      <property
        name="deliveryDate"
        column="delDate"
        type="date"/>
   
    <set
      name="boxes"
      table="box"
      inverse="true"
      outer-join="true"
      cascade="save-update">
      <key column="delivery_did"/>
      <one-to-many class="test.hibernate.Box"/>
    </set>
   
    <set
      name="toys"
      table="toy"
      inverse="true">
      <key column="delivery_did"/>
      <one-to-many class="test.hibernate.Toy"/>
    </set>
   </class>
</hibernate-mapping>

<hibernate-mapping>
   <class
     name="test.hibernate.Toy"
     table="toy">


     <id
        name="toyID"
        column="tid"
        unsaved-value="null"
        access="field"
        type="integer">        
        <generator class="native"/>
     </id>

    <version name="version" access="field" column="version" type="integer"/>

      <property
        name="description"
        column="descr"
        type="string"/>

   
      <many-to-one
        name="delivery"
        column="delivery_did"
        class="test.hibernate.Delivery"
        not-null="true"/>

      <many-to-one
        name="box"
        column="box_bid"
        class="test.hibernate.Box"
        not-null="false"/>       
   </class>

</hibernate-mapping>

        System.out.println("Starting test ...");

        Configuration config = new Configuration();
        SessionFactory sf = config.configure().buildSessionFactory();

        System.out.println("Loading Delivery ...");

        Session s = sf.openSession();
        Delivery d = (Delivery) s.find("from Delivery").get(0);
        s.close();
        s = sf.openSession();

        Delivery origDelivery = (Delivery) s.find("from Delivery").get(0);
        s.close();

        s = sf.openSession();

        Transaction t = s.beginTransaction();

        // create new box and add it to delivery and add a toy
        Box b = new Box();
        b.setDelivery(d);
        d.getBoxes().add(b);

        Toy toy = (Toy) d.getToys().iterator().next();
        toy.setBox(b);
        b.getToys().add(toy);

        // lock original delivery
        s.lock(origDelivery, LockMode.NONE);

        // save the changed delivery
        s.saveOrUpdateCopy(d);
        t.commit();
        s.close();

21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - processing cascades for: test.hibernate.Box
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - cascading to collection: test.hibernate.Box.toys
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - done processing cascades for: test.hibernate.Box
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - processing cascades for: test.hibernate.Box
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - cascading to collection: test.hibernate.Box.toys
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - cascading to saveOrUpdate()
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - version unsaved-value strategy UNDEFINED
21515 [main] DEBUG net.sf.hibernate.engine.Cascades  - id unsaved-value strategy NULL
21515 [main] DEBUG net.sf.hibernate.impl.SessionImpl  - saveOrUpdate() previously saved instance with id: 37
21515 [main] DEBUG net.sf.hibernate.impl.SessionImpl  - updating [test.hibernate.Toy#37]
net.sf.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: 37, of class: test.hibernate.Toy
   at net.sf.hibernate.impl.SessionImpl.checkUniqueness(SessionImpl.java:1687)
   at net.sf.hibernate.impl.SessionImpl.doUpdateMutable(SessionImpl.java:1470)
   at net.sf.hibernate.impl.SessionImpl.doUpdate(SessionImpl.java:1490)
   at net.sf.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:1419)
   at net.sf.hibernate.engine.Cascades$4.cascade(Cascades.java:115)
   at test.hibernate.TestHibernate.main(TestHibernate.java:62)
Exception in thread "main"