I have some queries about Hibernate:

a) if I have a 4 level deep Class Hierarchy and want to update a member at the bottom level I could set up a cascade="all-delete-orphan" at various levels and issue an update of the instance at the top of the hierarchy. Or could I just do a simple update on the instance at the bottom of the hierarchy explicitly ? The pdf doco (P. 52) recommends doing an update at the top (the dependent is a LifeCycle object). However this sounds inefficient since won't Hibernate have to navigate through the various objects in the Obejct Graph ?

b) P. 53 of the doco says that "Furthermore a mere reference to a child from a persistent parent will result in a save / update of the child". So if I read some children it will perform updates ?

c) Is there any concept of a isModified() tag like in WebLogic where the update will only occur if something has changed on the instance ? In our previous architecture we implemented something like that and let our persistence mechanism detect changes via the tag and perform the required update. Hibernate sounds more along the lines of getting the business logic to explicitly perform the update explicitl

If you load an object from a session A, the object will be updated when flushing the session A (wether you saveOrUpdate it or not).

If you indirectly load an object


it will be updated whan flushing session.

It you linked a transient object with another one (parent and cascaded) :
* if the parent is transient, save the parent and the child will be saved
* if the parent is persistent, the the child will be saved because of cascade.

You don't have to load the whole association tree.
Let's have A -> B -> C -> D

If I want to update D,
session.load(D);
//change D
//session.flush();

If I want to change D from a C
session.load(C)
c.setD(new D());
session.flush();

No need to load A.

Hope this help