Question

i know this question might be asked before, but i want to make it specific,

am using hibernate without annotations, so my case is if I’ve the following relation:

A has many of B and B has one of A, it’s a one to many relation from A side, am dealing with A entity which contain set of B, then when Creating, Updating Bs in runtime using A, then saving or updating A using hibernate, i want it also to save or update B i.e cascade save delete but from the side of A (one to many), i think it’s allowed from B (many to one) side only

Regads,

Answer 1

I’m not sure I understood the question but it’s definitely possible to define operations to cascade for a one-to-many association (see the section 6.2. Collection mappings). Below, an extract from the Chapter 21. Example: Parent/Child:

21.3. Cascading life cycle

You can address the frustrations of
the explicit call to save() by using
cascades.

<set name="children" inverse="true" cascade="all">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

This simplifies the code above to:

Parent p = (Parent) session.load(Parent.class, pid);
Child c = new Child();
p.addChild(c);
session.flush();

Similarly, we do not need to iterate
over the children when saving or
deleting a Parent. The following
removes p and all its children from
the database.

Parent p = (Parent) session.load(Parent.class, pid);
session.delete(p);
session.flush();

However, the following code:

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
c.setParent(null);
session.flush();

will not remove c from the database.
In this case, it will only remove the
link to p and cause a NOT NULL
constraint violation. You need to
explicitly delete() the Child.

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
session.delete(c);
session.flush();

In our case, a Child cannot exist
without its parent. So if we remove a
Child from the collection, we do want
it to be deleted. To do this, we must
use cascade="all-delete-orphan".

<set name="children" inverse="true" cascade="all-delete-orphan">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

Even though the collection mapping
specifies inverse="true", cascades are
still processed by iterating the
collection elements. If you need an
object be saved, deleted or updated by
cascade, you must add it to the
collection. It is not enough to simply
call setParent().

References

• 6.2. Collection mappings
• Chapter 21. Example: Parent/Child