Question

I need this roadmap of a Hibernate managed object instance.

First, I create an instance with initial properties and persist this object in a db.
Then session associated with this object is closed.
But still, I serialize my object and on the next step deserialize it, invoke some setters,
and again, I need to update what changed in a database.

What methods of Hibernate session should I use?
persist() or save() on the first step and saveOrUpdate() on the second?

In fact I see that saveOrUpdate() can be used on each step. The only problem is that as I see,
it does not return an associated PK. Do you know how to get it when we persist the object for the
first time? I suppose, after we persist the object, it gets an id field set, so
after invokation of saveOrUpdate(myObject), myObject.getId() returns the PK?

What would you recommend?

Answer 1

If I do understand your problem, you want to reattach a transient object to a new hibernate session. Then you should use Session.merge(object)

merge

Object merge(Object object)
throws HibernateException

Copy the state of the given object
onto the persistent object with the
same identifier. If there is no
persistent instance currently
associated with the session, it will
be loaded. Return the persistent
instance. If the given instance is
unsaved, save a copy of and return it
as a newly persistent instance. The
given instance does not become
associated with the session. This
operation cascades to associated
instances if the association is mapped
with cascade=”merge”.