Many-to-one owner to cascade on deletion of owned entity

Froestel · **Posted:** Wed Sep 16, 2009 11:48 am

Hi there,

my task is to delete an entity B that holds a many-to-one reference to an entity A as soon as the referenced entity A is deleted -- basically a cascade delete in the DB. The association is unidirectional and entity A does not "know" about entity B.

Java code:

Code:

public abstract class RootEntity {
  private Long id;
  ...
  public Long getId() { ... }
}

public class EntityA extends RootEntity {
  ...
}

public class Entity B extends RootEntity {
  protected EntityA;
  ...
  public EntityA getEntityA() { ... }
}

Hibernate mapping:

Code:

<hibernate-mapping ...>
<class name="RootEntity" abstract="true" ...>
    <id name="id" type="long">
      <generator class="native" />
    </id>
    ...

    <subclass name="EntityA" extends="RootEntity">
      <join table="entitya">
        <key column="id" foreign-key="FK_A_Root" />
        ...
      </join>
    </subclass>

  <subclass name="EntityB" extends="RootEntity">
      <join table="entityb">
        <key column="id" foreign-key="FK_B_Root" />
        ...
        <many-to-one name="entitya" column="entitya_id"
          class="EntityA" foreign-key="FK_B_A"
          not-null="true" update="false" />
      </join>
    </subclass>
    ...
</class>
</hibernate-mapping>

The relationship is not unique, there may be several instances of EntityB referencing the same EntityA.

I want to achieve that the foreign key FK_B_A is marked ON DELETE CASCADE. How do I do that?

BTW: It is not intended to make EntityB known to EntityA by adding a reference or a collection of references to it.

CU
Froestel