I inherited some code and am new to Spring and Hibernate.

1)
I have a problem where I am getting an exception in my tomcat log (HibernateOptimisticLockingFailureException)
and believe it is this:

Thread1: A line of code reads some data from the DB (a row from a table) into a hibernate ojbect
Thread2: thread2 comes along and writes some data to the table and row that was read by thread1
Thread1: thread1 then makes some change to a field in the object and tries to write to the DB

Is this the scenario that is causing this problem? Can anyone confirm this or is there some other
scenario that would cause the problem?

Would doing a "merge" instead of an "update" on both of the rows in thread 1 and thread 2 solve the issue?

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2)
Is doing a merge the appropriate thing to do here? I am trying to find out more about the concept of "merge". I googled it but there was no detailed explanation.

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3)
Also where can I find the *line* of code in thread 1 that read the data and tried
to save it after thread 2 beat thread 1 to it. The lines listed in the stack trace stop
way before any save to the database ocurrs. Because hibernate wraps everything, I believe
there is some lower level jdbc debug statements that I am missing.

http://www.hibernate.org/hib_docs/entit ... state.html
Please have a look into the above link to understand the merge() usage.