Hibernate: update same object in different session

Question

I'm trying to do that but not working, can anyone suggest me what i'm wrong? In the end I lose the first update

    EntityManager entityManager1 = JPAUtil.getEntityManagerFactory().createEntityManager();
    EntityManager entityManager2 = JPAUtil.getEntityManagerFactory().createEntityManager();

    Session session1 = (Session) entityManager1.getDelegate();
    Prova prova1 = session1.load(Prova.class, "020");

    Session session2 = (Session) entityManager2.getDelegate();
    Prova prova2 = session2.load(Prova.class, "020");

    prova2.setDes(prova2.getDes() + " 2");    
    prova1.setShortdes(prova1.getShortdes() + " 1");

    Transaction t2 = session2.beginTransaction();
    session2.update(prova2);
    t2.commit();
    session2.close();

    Transaction t1 = session1.beginTransaction();
    session1.update(prova1);
    t1.commit();
    session1.close();

Answer 1

As the previous answer you always need to check the version of object before saving. Hibernate or JPA has features called optimistic locking to fix this issue. Refer to the below code and link for more information.

@Entity
public class Employee 
{
  @Id
  @GeneratedValue
  private Integer id;
  @Version
  private long version;
  private String name;
}

When you create employee record the framework will automatically create version value. At first lets assume the values are

[1, 0, "name1"]

On update it changes to

[1, 1, "name2"]

On next update it changes to

[1, 2, "name3"]

The framework will throw exception if you try to update data with wrong version

Link has more information on this https://www.logicbig.com/tutorials/java-ee-tutorial/jpa/optimistic-lock.html