MergeClone in Toplink 10.1.3

Question

I have an object model with Booking and Status objects, where Booking has 1-1 relationship with Status.
Since we're using Webservices, we try to perform update on the object returned by webservice with MergeClone as follows:
          Session session = getSession();
          UnitOfWork uow = session.acquireUnitOfWork();
          uow.registerObject(booking);
          uow.mergeCloneWithReferences(booking);
          uow.commit();
However, I got SQL Exception when commit:
Internal Exception: java.sql.SQLException: ORA-00001: unique constraint (CS2_DEV_EXERCISE.SYS_C007756) violated
Error Code: 1
Call:INSERT INTO TEST_NGSC_BOOKING (BookingID, Name, version, StatusID) VALUES (101, 'changed', 1, NULL)
Query:InsertObjectQuery(booking[101, changed, null, 1] )
It is strange to me that Toplink generate "Insert" statement, but actually the record is already stored in DB, and the PK matched with the object I passed to "mergeClone" call.
I tried again by reading the Object 1st:
          UnitOfWork uow = session.acquireUnitOfWork();
          uow.registerObject(uow.readObject(booking));
          uow.mergeCloneWithReferences(booking);
          uow.commit();
Then I got another exception:
Exception [TOPLINK-5006] (Oracle TopLink - 10g Release 3 (10.1.3.1.0) (Build 061004)): oracle.toplink.exceptions.OptimisticLockException
Exception Description: The object [booking[101, changed, null, 1] ] cannot be updated because it has changed or been deleted since it was last read.
Class> com.cargosmart.toplink.test.Booking Primary Key> [101]
Please kindly advice if I have done anything wrong in my code
Many Thanks

Answer 1

For the case:
uow.registerObject(uow.readObject(booking));
uow.mergeCloneWithReferences(booking);
uow.commit();
The same exception thrown as before:
Exception [TOPLINK-5006] (Oracle TopLink -
10g
Release 3 (10.1.3.1.0) (Build 061004)):
oracle.toplink.exceptions.OptimisticLockException
Exception Description: The object [status[51,null,
null, 1] ] cannot be updated because it haschanged
or been deleted since it was last read.
Class> com.cargosmart.toplink.test.Status
Primary
Key> [51]Can you add this line of code after you issue
uow.commit() ?
uow.getUnitOfWorkChangeSet().hasChanges();
If this is false that means there are no changes.
You need to ensure that when the object is sentback
over the wire there are indeed changes or elsewhen
the comparison happens and there are no changes
no
updates will be written.
I was able to reproduce one of your problems(the
unique key violation) but was unable toreproduce
the
optimistic lock exception.I was able to reproduce the optimistic lockexception
as well. On your web services client side code you
have invoked a method that changes the version
attribute on the booking class. The versionattribute
is one that Toplink manages not the developer.Check
to see if this is happening.Thanks for reminding!
Yes, the problem is related to the version field.
I need to take special care on the version value by
performing the "readObject", get the existing version
value and fit into the changed object before
performing mergeClone, and then I was able to commit
the change into DB successfully.I understand that you have to do a "readObject" before you merge to avoid the unique constraint violation exception(the object may no longer be in the cache when you merge especially if you set the Existence check to "Check Cache"). But I am not sure updating the version field is recommended. You may want to confirm that of course.