SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
           
session = sessionFactory.openSession();
Person p1 = new Person(10,"aaaa");
session.merge(p1.getClass().getName(),p1);
         
Transaction tnx = session.beginTransaction();
Person p = new Person(10,"aaaa");
Object res =session.merge(p.getClass().getName(),p);
session.delete(res);
         
session.merge(p.getClass().getName(),p1);
tnx.commit();