JPA thinks I'm deleting a detached object

Question

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)  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?

Answer 1

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.

Answer 2

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

The above code is similar to that proposed by zawhtut