Hi,

I was having a hard time to make hibernate update one object on my application. The process ended up in the following exception being thrown:


After looking for answers at this forum, I changed my update method to call getHibernateTemplate().merge(object) instead of getHibernateTemplate().saveOrUpdate(object) and now everything works as expected. No exceptions and the update process is executed.

It works and that's ok, but I'm not sure if this is just a workaround to avoid further problems or it is an acceptable solution. Is there someone here who can shed some light on this?

Thanks in advance!

I'm going to use these terms, so let me list them first.

transient: never persistent, not associated with any Session
persistent: associated with a unique Session
detached: previously persistent, not associated with any Session

I'm guessing the object you are trying to update is a "persistent" object, i.e. you open a hibernate session, load the object, make changes to it, and call saveOrUpdate before closing the session.

The save operation will try to make a transient object persistent. Since your object is persistent, it won't use this. It will attempt the update instead.

This is a quote from Hibernate's javadoc for update.

"Update the persistent instance with the identifier of the given detached instance. If there is a persistent instance with the same identifier, an exception is thrown."

And that is why you see the exception.

Merge, on the other hand works with both detached and persistent objects.

Really if you are dealing with persistent objects. You don't have to explicitly call saveOrUpdate. When the session closes, your object will be automatically updated.