Multiple copies of an object in a session

dmmorris · **Posted:** Wed Dec 10, 2003 7:19 pm

How do you retrieve an entity object in a session without getting a new copy? I have a developer that is doing a session.load() for an object and then an update. The update is saying the object's Id is a duplicate of an existing object in the session.

I walked through his code and it sure appeared that he is retrieving the list in one session and doing the load in another but that must not be the case. I think there are some design issues in re-retrieving the object but I wonder how would you reload an object -- let's say you had two classes working against a common database?

dimas · **Posted:** Wed Dec 10, 2003 8:06 pm

I'm not sure I understand your question :)
But if it is about reloading already loaded object from the database - session.refresh() will help.

emmanuel · **Posted:** Thu Dec 11, 2003 5:59 am

dmmorris wrote:

How do you retrieve an entity object in a session without getting a new copy?

You don't have a copy.
If you did session.load() then the object is already linked to the session. Then it don't have to be session.update

drj · **Posted:** Thu Dec 11, 2003 6:31 am

Code:

Object o = new Object();
session.load(Object, Serializable)

loads the object with the given identifier into the given transient instance. You run the risk of having multiple instances of the Object for a particular session.

Code:

Object o = session.load(Class, Serializable)

returns the persistant object (possibly from the cache) with the given identifier.

Justin

dmmorris · **Posted:** Thu Dec 11, 2003 2:41 pm

I built a test that duplicates his problem. He has several classes that reference each other. Class A is referenced indirectly by Class B via Class C. He is running:

load A
make changes to A
hql query C -- this also retrieves a copy of B which gets a copy of A.
if C is OK then update A

He tells me that it is a problem to move load A/change A after the query to C

I will see what it will take to restructure the code since there doesn't appear to be any way to override this behavior.

emmanuel · **Posted:** Fri Dec 12, 2003 6:56 am

Actually Hibernate will flush the session before the HQL of C since C is kind of related to A. So A is already updated before your HQL.

No particular pb to load A after reading C

dmmorris · **Posted:** Fri Dec 12, 2003 3:02 pm

I agree that is what I expected but here is the actual code:

Code:

         // Create Another Session
            ThreadLocalSession.setSession(new ServiceSession());

            // Update Record            
            ThreadLocalSession.getSession()
                              .beginTransaction();
                              

         adjustmentApprovalService.load(adjustmentApproval.getAdjustmentApprovalId());
         CashReceiptsDetail crDtl = (CashReceiptsDetail) crdService.load(crdId);            adjustmentApproval.setAdjustmentAmount(999.99);
            adjustmentApprovalService.update(adjustmentApproval);
            ThreadLocalSession.getSession()
                              .commit();

            // Close Session
            ThreadLocalSession.getSession()
                              .close();

This code fails on the update because the crDtl object causes the adjustmentApproval object to be read. I fixed it by using saveOrUpdateCopy.

emmanuel · **Posted:** Sat Dec 13, 2003 6:09 am

I told you no particular pb to load A after reading C, I did not say no particular pb to update a transiant A after reading the persistent A