bidirectional association between component and entity

thofis · **Posted:** Tue Jun 06, 2006 12:47 pm

Hibernate version:
3.1.2

Mapping documents:

Code:

<hibernate-mapping package="component">
   <class name="EntityA" table="ENTITYA">
   
      <id name="id" column="ID" type="long">
         <generator class="increment"/>
      </id>
         
      <component name="myComponent" class="ComponentA" >
         
         <parent name="myEntity"/>
         
         <property name="title" column="TITLE" type="string"/>
         
         <set name="entityBs">
            <key column="A_ID"></key>
            <one-to-many class="EntityB"></one-to-many>
         </set>
         
      </component>
      
   </class>
</hibernate-mapping>

I'm trying to map a bidirectional association between a component of type "ComponentA" -which is part of an entity of type "EntityA" - to an entity of type "EntityB". The unidirectional association from above works, but I couldn't figure out how the mapping for the many-to-one-element on the other side would have to look like.

I tried this...

Code:

<hibernate-mapping package="component">
   
   <class name="EntityB" table="ENTITYB">
   
      <id name="id" column="ID" type="long">
         <generator class="increment"/>
      </id>

      <many-to-one name="component" class="ComponentA" column="A_ID">
      </many-to-one>

   </class>
</hibernate-mapping>

... and got an error like this from hbm2ddl:

An association from the table ENTITYB refers to an unmapped class: component.ComponentA

The same happens, if I omit the class-attribute.

Is there a way to get this kind of association work?

Thanx in advance!

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

No. Components are values, not entities, and thus cannot be the "target" of an association like this. Change your component to a proper mapped entity to do this.

thofis · **Posted:** Thu Jun 08, 2006 4:44 am

Thanx, for answering.

I can stop my experiments with this kind of association now...

I thought I would have the freedom to decide, if two java-classes with a one-to-one association use a common database table (component-mapping) or use two database tables (<one-to-one>mapping with two entities).

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

We do. The decision is whether or not you want

an entity, that can be stand-alone or be referred to from any other entity, or
a value, that has no life of its own and is 100% dependent on the entity that wraps it.