JPA thinks I'm deleting a detached object

I've got a DAO that I used to load and save my domain objects using JPA. I finally managed to get the transaction stuff working, now I've got another issue.

In my test case, I call my DAO to load a domain object with a given id, check that it got loaded and then call the same DAO to delete the object I just loaded. When I do that I get the following:

java.lang.IllegalArgumentException: Removing a detached instance mil.navy.ndms.conops.common.model.impl.jpa.Group#10
 at org.hibernate.ejb.event.EJB3DeleteEventListener.performDetachedEntityDeletionCheck(EJB3DeleteEventListener.java:45)
 at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:108)
 at org.hibernate.event.def.DefaultDeleteEventListener.onDelete(DefaultDeleteEventListener.java:74)
 at org.hibernate.impl.SessionImpl.fireDelete(SessionImpl.java:794)
 at org.hibernate.impl.SessionImpl.delete(SessionImpl.java:772)
 at org.hibernate.ejb.AbstractEntityManagerImpl.remove(AbstractEntityManagerImpl.java:253)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 at java.lang.reflect.Method.invoke(Method.java:600)
 at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:180)
 at $Proxy27.remove(Unknown Source)
 at mil.navy.ndms.conops.common.dao.impl.jpa.GroupDao.delete(GroupDao.java:499)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 at java.lang.reflect.Method.invoke(Method.java:600)
 at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:304)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
 at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
 at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
 at $Proxy28.delete(Unknown Source)
 at mil.navy.ndms.conops.common.dao.impl.jpa.GroupDaoTest.testGroupDaoSave(GroupDaoTest.java:89)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:48)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 at java.lang.reflect.Method.invoke(Method.java:600)
开发者_开发百科 at junit.framework.TestCase.runTest(TestCase.java:164)
 at junit.framework.TestCase.runBare(TestCase.java:130)
 at junit.framework.TestResult$1.protect(TestResult.java:106)
 at junit.framework.TestResult.runProtected(TestResult.java:124)
 at junit.framework.TestResult.run(TestResult.java:109)
 at junit.framework.TestCase.run(TestCase.java:120)
 at junit.framework.TestSuite.runTest(TestSuite.java:230)
 at junit.framework.TestSuite.run(TestSuite.java:225)
 at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
 at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
 at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

Now given that I'm using the same DAO instance, and I've not changed EntityManagers (unless Spring does so without letting me know), how can this be a detached object?

My DAO code looks like this:

public class GenericJPADao<INTFC extends IAddressable, VO extends BaseAddressable> implements IWebDao, IDao<INTFC>, IDaoUtil<INTFC>
{
    private static Logger logger = Logger.getLogger (GenericJPADao.class);

    protected Class<?> voClass;

    @PersistenceContext(unitName = "CONOPS_PU")
    protected EntityManagerFactory emf;

    @PersistenceContext(unitName = "CONOPS_PU")
    protected EntityManager em;

    public GenericJPADao()
    {
        super ( );

        ParameterizedType genericSuperclass = 
                        (ParameterizedType) getClass ( ).getGenericSuperclass ( );
        this.voClass = (Class<?>) genericSuperclass.getActualTypeArguments ( )[1];
    }


    ...


    public void delete (INTFC modelObj, EntityManager em)
    {
        em.remove (modelObj);
    }

    @SuppressWarnings("unchecked")
    public INTFC findById (Long id)
    {
        return ((INTFC) em.find (voClass, id));
    }
}

The test case code looks like:

IGroup loadedGroup = dao.findById (group.getId ( ));
assertNotNull (loadedGroup);
assertEquals (group.getId ( ), loadedGroup.getId ( ));

dao.delete (loadedGroup); // - This generates the above exception

loadedGroup = dao.findById (group.getId ( ));
assertNull(loadedGroup);

Can anyone tell me what I'm doing wrong here?

I suspect that you are running your code outside a transaction so your find and delete operations occur in a separate persistence context and the find actually returns a detached instance (so JPA is right and you ARE deleting a detached object).

Wrap your find / delete sequence inside a transaction.

Update: Below an excerpt of the chapter 7.3.1. Transaction Persistence Context:

If you use an EntityManager with a transaction persistence context model outside of an active transaction, each method invocation creates a new persistence context, performs the method action, and ends the persistence context. For example, consider using the EntityManager.find method outside of a transaction. The EntityManager will create a temporary persistence context, perform the find operation, end the persistence context, and return the detached result object to you. A second call with the same id will return a second detached object.

public void remove(Object obj){
    em.remove(em.merge(obj));
}

The above code is similar to that proposed by zawhtut

+1 to Pascal Thivent's post and just a followup.

    @Transactional
    public void remove(long purchaseId){
        Purchase attached = jpaTemplate.find(Purchase.class,purchaseId);
        jpaTemplate.remove(attached);
    }

Get the instance by using em.getReference() instead of em.find().

For instance, try:

em.remove(em.getReference(INTFC.class, id)); 

Here is what I used (based on the previous answers)

public void deleteTask(int taskId) {
    Task task = getTask(taskId); //this is a function that returns a task by id
    if (task == null) {
        return;
    }
    EntityManager em = emf.createEntityManager();
    EntityTransaction et = em.getTransaction();
    et.begin();
    em.remove(em.merge(task));
    et.commit();
    em.close();
}

Transaction ensures the ACID properties but not whether the entity is attached or detached. Even if you are running entityManager.find and entityManager.remove() in the same transaction , there is not guarantee that the entity will be attached. So before issuing entityManager.remove() check if the entity is attached, if not attach it using enitityManger.merge(entity) and then issue entityManager.remove on it as follows:

@Transactional
 public void delete (long id)
    {
ModelObj modelObj=entityManager.find(ModelObj.class,id);
modelObj=entityManager.contains(modelObj)?modelObj:entityManager.merge(modelObj);
        em.remove (modelObj);
    }

What worked for me was calling flush so the changes are made as in the following example:

@PersistanceContext
EntityManager em;

public SomeObject(...parameters){
    repository.save();
    em.flush();
    repository.delete();
}