JPA Hibernate - changing the primary key of an persisted object

Question

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

I couldn't find an answer to this problem so I would appreciate your help here.The code is:

    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();

Maybe you should take a look into this http://stackoverflow.com/questions/734461/hibernate-alter-identifier-primary-key — Iker Aguayo, Jan 09 '14 at 11:24
Why change the primary key of the object? Also, if you do change the primary key of the object then how is it going to be guaranteed that it is unique? — Hrishikesh, Jan 09 '14 at 15:17

score 18 · Accepted Answer · answered Jan 09 '14 at 11:25

18

You should never modify the primary key of a an entity - this define the identify of the object and it makes no sense to change it.

If you really do need that - you'd be better of deleting the entity and creating a new one which just copies the old one but with a new primary key. This way, if you have any constraints - such as foreign keys pointing to the old identifier - you'll know about it.

Also check out the "Identity and Sequencing" section here.

Hope this helps.

answered Jan 09 '14 at 11:25

Eugen

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You're right-it's not better to modify the PK of an entity.But is it possible to do that in JPA with Hibernate? (without deleting and creating new entity ) – Martinas Maria Jan 09 '14 at 16:23
4

Not possible in Hibernate no - you'd have to do it in raw SQL. – Eugen Jan 09 '14 at 16:36
2

You could detach the entity with entityManager.detach(aa); – Rohith Nandakumar Oct 22 '18 at 10:16

JPA Hibernate - changing the primary key of an persisted object

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