how to define an inverse cascade delete on a many-to-one mapping in hibernate
Solution 1
Hibernate only cascades along the defined associations. If A knows nothing about Bs, nothing you do with A will affect Bs.
Pascal's suggestion is, therefore, the easiest way to do what you want:
<class name="A" table="tbl_A">
...
<set name="myBs" inverse="true" cascade="all,delete-orphan">
<key column="col1"/>
<one-to-many class="B"/>
</set>
</class>
<class name="B" table="tbl_B">
...
<many-to-one name="a" class="A" column="col1" not-null="true"/>
</class>
Note that setting cascade="delete"
on B
as you have it in your original code will NOT do what you want - it tells Hibernate to "delete A if B is deleted" which is likely to result in constraint violation (if there are any other Bs linked to that A).
If you absolutely cannot add a collection of Bs to A (though I can't really think of the circumstances where that'd be the case), your only other alternative is to define cascade delete from A to B at the foreign key level; your Bs will then be deleted when your A is deleted.
This is a rather ugly solution, however, because you have to be extremely careful of how you delete A in Hibernate:
- Session must be flushed prior to deleting A (having pending updates to B may result in an error or A and some Bs being re-inserted behind the scenes)
- All Bs linked to your A (and since you're not maintaining the relationship from A side that means all Bs) must be evicted from all active sessions and 2nd level cache.
Solution 2
I think you need to cascade="all,delete-orphan"
from A to B's with a one-to-many
association.
Comments
-
Monis Iqbal almost 2 years
I have two classes A and B. Many B's can have association with a single A, hence a many-to-one relationship from B to A. I've mapped the relationship like:
<class name="A" table="tbl_A"> <property name="propA" column="colA"/> </class> <class name="B" table="tbl_B"> <property name="propB" column="colB"/> <many-to-one name="a" class="A" column="col1" cascade="delete"/> </class>
A has nothing mapped to B. Keeping this in mind we intend to delete B when it's associated A is deleted. This could have been possible if I could define an inverse="true" on the many-to-one association in B but hibernate does not allow that.
Can anyone help with this? We do not want to write anything in A for this.