java.lang.IllegalArgumentException: Removing a detached instance com.test.User#5

Question

I have a java EE project using JPA (transaction-type="JTA"), hibernate as provider. I write my beans to handle the CRUD things. The program running in JBOSS 7 AS.

I have an EntityManagerDAO :

@Stateful public class EntityManagerDao implements Serializable {      @PersistenceContext(unitName = "dtdJpa")     private EntityManager entityManager;      @TransactionAttribute(TransactionAttributeType.REQUIRED)     public Object updateObject(Object object) {         object = entityManager.merge(object);         return object;     }      @TransactionAttribute(TransactionAttributeType.REQUIRED)     public void createObject(Object object) {         entityManager.persist(object);     }      public void refresh(Object object) {         entityManager.refresh(object);     }      public <T> T find(Class<T> clazz, Long id) {         return entityManager.find(clazz, id);     }      @TransactionAttribute(TransactionAttributeType.REQUIRED)     public void deleteObject(Object object) {         entityManager.remove(object);     } } 

but when I invoke deleteObject, this exception comes out.

java.lang.IllegalArgumentException: Removing a detached instance com.test.User#5

How is this caused and how can I solve it?

Answer 1

EntityManager#remove() works only on entities which are managed in the current transaction/context. In your case, you're retrieving the entity in an earlier transaction, storing it in the HTTP session and then attempting to remove it in a different transaction/context. This just won't work.

You need to check if the entity is managed by EntityManager#contains() and if not, then make it managed it EntityManager#merge().

Basically, the delete() method of your business service class should look like this:

em.remove(em.contains(entity) ? entity : em.merge(entity));