Create a persistent object A Set some properties (String) on A : A.setName("toto") Persist A and commit

Load A using id based find Change some properties values on A but DO NOT MERGE A Create new persistent object B and copy the properties (including modifed ones) of A in B : B.setName(A.getName()) Persiste B and commit

Change reference of A with B : A = B Merge A

This usecase cause the Entity A and B to be persisted with same values even if A has not been really merged because of switching reference !

Test case visible on github at : https://github.com/jayblanc/hibernate-test