Multilevel class hierarchy

palantonio · **Joined:** Tue Aug 01, 2006 11:47 am **Posts:** 2

I' using Hibernate 2 and I' m trying to map a multilevel class hierarchy.
I used a table per subclass mapping.
A leaf class has a many-to-one association.
When I try to save an object of this leaf class, the object is saved,
but doesn' t the collection associated to the object.
Does anyone know how can I make a correct multilevel class hierarchy mapping?

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

You'll have to be more explicit, as what you've given is a bit confusing. There's a many-to-one association, and a collection, in the same subclass? And you want a save to be cascade to the collection? I'm confused.

palantonio · **Joined:** Tue Aug 01, 2006 11:47 am **Posts:** 2

Excuse me for my imprecision.
This is an example of my mapping:

Code:

    <class name="ClassA" table="CLASS_A">
        <id name="id" type="long" column="ID" unsaved-value="null"> 
            <generator class="hilo">
                <param name="table">CLASA_HI_VALUE</param>
                <param name="column">NEXT_VALUE</param>
                <param name="max_lo">100</param>
            </generator>
        </id>
        <property name="name" type="string" column="NAME" not-null="true" />
        <property name="description" type="string" column="DESCRIPTION" />
        <set name="messages" table="MESSAGES_CLASSA" >
            <key column="CLASSA_ID" />
            <many-to-many class="Message" column="MESSAGE_ID" /> 
        </set>                  
        <joined-subclass name="ClassB" table="CLASS_B">
            <key column="ID" />
            <property name="property1" type="string" column="PROPERTY_1" />
            <property name="property2" type="int" column="PROPERTY_2" />
        </joined-subclass>
        <joined-subclass name="ClassC" table="CLASS_C">
            <key column="ID" />
            <property name="property3" type="string" column="PROPERTY_3" />
            <property name="property4" type="int" column="PROPERTY_4" />
            <property name="property5" type="int" column="PROPERTY_5" />
            <set name="objectSet" inverse="true" cascade="all-delete-orphan" >
           <key column="CLASSC_REF" />
           <one-to-many class="MyClass" />
            </set>
            <joined-subclass name="ClassD" table="CLASS_D">
           <key column="ID" />
                <property name="property6" type="int" column="PROPERTY_6" />
            </joined-subclass>
            <joined-subclass name="ClassE" table="CLASS_E">
           <key column="ID" />
                <property name="property7" type="int" column="PROPERTY_7" />
            </joined-subclass>
        </joined-subclass>
    </class>

    <class name="MyClass" table="MYCLASS">
        <id name="id" type="long" column="ID" unsaved-value="null"> 
            <generator class="hilo">
                <param name="table">MYCLASS_ID_HI_VALUE</param>
                <param name="column">NEXT_VALUE</param>
                <param name="max_lo">100</param>
            </generator>
        </id>
        <many-to-one name="objectClassC" class="ClassC" column="CLASSC_REF" cascade="all" />
        <property name="myproperty" type="int" column="MYPROPERTY" />
    </class>

As you can see, ClassC has 2 subclasses: ClassD and ClassE.
Moreover, ClassC has a Set of MyClass objects.
This is the code I use to create a ClassD object with a new set of
MyClass objects:

Code:

    ClassD obj = new ClassD();
    ....
    ....
    MyClass myobj = new MyClass();
    ....
    myobj.setObjectClassC(obj);
    obj.getObjectSet().add(myobj);
    ....
    tx = sess.beginTransaction();
    session.save(obj);
    tx.commit();

obj is saved, but doesn' t myobj.
Therefore, in the database obj has an empty set.

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

You have inverse="true" on the objectSet <set>. This tells hibernate that it is allowed put existing items into the set, and remove items from the set, but it's not allowed to create or delete items. Remove the inverse="true" to make it work, or explicitly save myobj before saving obj.