Question

Maybe this question has been anwsered, maybe not.

I want to update an object with optimistic lock, using

...
EntityManager.merge(...);
EntityManager.flush(...);
...

My code works fine. What I want is update the version number in object and keep object reference.

I googling a long time, but I did not found the answer.

My last resort is make a nativeQuery and get the version number.

Here is the a test code:

    EntityManagerFactory factory = Persistence.createEntityManagerFactory(DBManager.getUnidadPersistencia());
    EntityManager emA = factory.createEntityManager();

    Grupo g = emA.find(Grupo.class, 1L);

    emA.close();

    //In some place 
    g.getSolicitanteList().get(0).setObservaciones("ZZZZ"); //Originally XXXX

    //...


    //Then I have to save the changes
    EntityManager emB = factory.createEntityManager();
    EntityTransaction tx = emB.getTransaction();

    try {
        tx.begin();
        emB.merge(g);
        emB.flush();
        tx.commit();
        //Here comes exception
        emB.refresh(g);
    } catch (Exception e) {
        if (tx.isActive()) {
            tx.rollback();
        }
        logger.log(Level.SEVERE, null, e);
    }
    emB.close();

And the stack trace:

30/07/2012 05:15:31 PM org.rp.co5parser.TestGrupo refreshTest
GRAVE: null
java.lang.IllegalArgumentException: Can not refresh not managed object: org.rp.co5parser.alojamiento.Grupo[ idGrupo=1 ].
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.refresh(EntityManagerImpl.java:943)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.refresh(EntityManagerImpl.java:849)
at org.rp.co5parser.TestGrupo.refreshTest(TestGrupo.java:89)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.apache.tools.ant.taskdefs.optional.junit.JUnit4TestMethodAdapter.run(JUnit4TestMethodAdapter.java:109)
at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:520)
at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:1060)
at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:911)

Is that ok?

Thanks in advance….

Answer 1

Before googling, read the documentation:

void refresh(java.lang.Object entity)

Refresh the state of the instance from the database, overwriting changes made to the entity, if any.

EDIT:

The error you get is not an OptimisticLockException. It’s an IllegalArgumentException with a pretty clear error message: Can not refresh not managed object. You may only refresh an entity which is managed. And the object you pass is a detached object.

You wouldn’t need to refresh the entity at all if you didn’t ignore the result of merge(). merge() takes a detached object, copies its state to the managed (attached) object with the same ID, and returns the managed object. So you should just need to do:

try {
    tx.begin();
    g = emB.merge(g); // assign the merged, attached object, having the new version to g
    tx.commit(); // no need to flush. commit flushes automatically
} catch (Exception e) {
    if (tx.isActive()) {
        tx.rollback();
    }
    logger.log(Level.SEVERE, null, e);
}
emB.close();