Copy the state of the given object onto the persistent object with the same identifier. If there is no persistent instance currently associated with the session, it will be loaded. Return the persistent instance. If the given instance is unsaved or does not exist in the database, save it and return it as a newly persistent instance. Otherwise, the given instance does not become associated with the session.

Copy the state of the given object onto the persistent object with the given identifier. If there is no persistent instance currently associated with the session, it will be loaded. Return the persistent instance. If there is no database row with the given identifier, save the given instance and return it as a newly persistent instance. Otherwise, the given instance does not become associated with the session.