title: JPA Hibernate - changing the primary key of an persisted object
body: <p>I am trying to change the id of an persisted object .I am using JPA with Hibernate and MySQL.
  The error I get when executing my code is :  org.hibernate.HibernateException: identifier of an instance of com.tutorial.jpa.certification.listing5_18.AA was altered from 2 to 99</p>
  
  <p>I couldn't find an answer to this problem so I would appreciate your help here.The code is:</p>
  
  <pre><code>    EntityManagerFactory emf=Persistence.createEntityManagerFactory("Tutorial");
      EntityManager em=emf.createEntityManager();     
      AA aa=em.find(AA.class, 2);
  
      em.getTransaction().begin();
      aa.setId(99);
      em.merge(aa);
      em.getTransaction().commit();
  </code></pre>