Java Hibernate Session in View Merge loses Changes? -

i have hibernate app trying implement open session in view pattern zk have question hibernate creates session per thread , closes have severals operations [criteria , save or update] methods in 1 session started implement using update method received infamous

nonuniqueobjectexception  

we have changed update() merge() question if following.

if have student class , trying update the student using update[making sure not in session avoid exception] later in other method student required updated again differently previous update time should merging , merge() method called. wondering when [flush][commit] method called changes first student loss? changes both students ok? happens??

i afraid changes in first student loss! can in case?

thanks lot best regards.

you should take @ locking algorithm. there 2 popular ones: optimistic , pessimistic. web application optimistic locking works better. long story short each revision of entity object given version label (often bigint or string db column). when pre-empt update , version became stale, hibernate throw optimistic lock exception, in case can capture , ask user (or take other appropriate measure)