I still do not understand the why after cascade=all, we do not have to call the save()? Can anyone explain to me?

The explicit call to save() is still annoying. We will address this 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();

hi jimmy

Not sure what your question is but can say that when cascade is set, Hibernate will treat the linked entities as being value types. Basically, cascaded operations will pass on.

Firstly, all operations on instances that are associated with (in) a Session are always persisted. So in your code, the creation of the relationship between the parent and child will be persisted immediately (not actually written immediately to the DB though). Of course, the child will not have been persisted when the call is made. Because cascade is set, Hibernate calls Session.saveOrUpdate(child) before it calls Session.saveOrUpdate(parent). If cascade wasnt set, you may get an error when the action is performed - because in a relation using a join table for example, HIbernate would try to add an entry to the collection table but it would refer to a child that didnt exist (in the DB).

http://www.hibernate.org/hib_docs/v3/re ... d-cascades

Happy hibernating

Michael

You have a look at the 2 flush there. How come the bottom one does not need the session.save(c)?