A different object with the same identifier value is already associated with the session

Today in the SSH2 project, there was this mistake, always feel that their code is not wrong, looking for a long time ....

Slag slag I in despair, suddenly fix!!!

Originally, I get the data from the database in the DAO layer to get a PO object, and then I have a method in the service layer to convert it to a Vo object

When I want to use him, I want to convert this Vo object into Po object, delete ...

The problem is out here ... Session is closed, from the Vo object again to the so-called Po object, can do the database operation again!!!

Simplify the tedious conversion, directly to the DAO directly manipulate PO objects can be

A different object with the same identifier value is already associated with the session