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Date: Sun, 12 Dec 2004 18:08:33 +0100
From: Jakob Braeuchi <jbraeuchi@gmx.ch>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Re: Bug and proposed patch
References: <cph95e$bl1$1@sea.gmane.org>
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hi tino,

just to make sure: your test-case is actually a 1:n collection.

how does your test differ from CollectionTest#testDeleteCollection or 
CollectionTest#testDeleteMainObjectWithOneToNRelation ?

in these testcases a main-object is deleted with it's associated 1:n children 
(when auto-delete = object).

jakob

Tino Sch�llhorn schrieb:
> Hi,
> 
> yesterday I posted a problem in the user-list (Deleting Main-Object and 
> its association-objects). Currently there are no answers for this 
> message. I looked further at the code of OJB. The method which is 
> interesting at this point is 
> PersistenceBrokerImpl.deleteCollections(Object, List).
> 
> Suppose you have the following case: Persons work at Projects with an 
> associated Role. Now if you are deleting a Person-Object or a 
> Project-Object you want to delete the corresponding Role-objects as well.
> 
> Normally one can achieve that with *auto-delete=object* at the 
> collections for the role-objects. But the current implementation does 
> not work here correctly. If one has 3 or more role objects to be handled 
> one gets a ConcurrentModificationException, like this one (line numbers 
> have changed because of some change from me):
> 
> java.util.ConcurrentModificationException
>     at 
> java.util.AbstractList$Itr.checkForComodification(AbstractList.java:448)
>     at java.util.AbstractList$Itr.next(AbstractList.java:419)
>     at 
> org.apache.ojb.broker.core.PersistenceBrokerImpl.deleteCollections(PersistenceBrokerImpl.java:701) 
> 
>     at 
> org.apache.ojb.broker.core.PersistenceBrokerImpl.doDelete(PersistenceBrokerImpl.java:514) 
> 
>     at 
> org.apache.ojb.broker.core.PersistenceBrokerImpl.delete(PersistenceBrokerImpl.java:466) 
> 
>     at 
> org.apache.ojb.broker.core.DelegatingPersistenceBroker.delete(DelegatingPersistenceBroker.java:170) 
> 
>     at 
> org.apache.ojb.broker.core.DelegatingPersistenceBroker.delete(DelegatingPersistenceBroker.java:170) 
> 
>     at kos.generator.DataObject.delete(DataObject.java:106)
>     at 
> kos.intranet2.sandbox.DeletePersonTest.runTest(DeletePersonTest.java:64)
>     at 
> kos.intranet2.sandbox.DeletePersonTest.main(DeletePersonTest.java:98)
> 
> 
> The current implementation looks like:
> 
> if (cds.getCascadingDelete() == bjectReferenceDescriptor.CASCADE_OBJECT) {
>     Object col = cds.getPersistentField().get(obj);
>         if (col != null)
>         {
>             while (colIterator.hasNext())
>                 {
>                     doDelete(colIterator.next());
>                 }
>         }
> }
> 
> And the ConcurrentModificationException is thrown at the call of doDelete.
> 
> If a am using OJB correctly this use-case should work. So I propose the 
> following (but perhaps imperformant and inelegant) patch: The idea is 
> simple. Instead of deleting the object immediately from its 
> origin-collection, copy the elements to another collection an use this 
> for deleting.
> 
> if (cds.getCascadingDelete() == bjectReferenceDescriptor.CASCADE_OBJECT) {
>     Object col = cds.getPersistentField().get(obj);
>         if (col != null)
>         {
>         // Inelegant and brutal. but it works
>          Collection c = new java.util.ArrayList();
>                  while (colIterator.hasNext()) {
>                      c.add(colIterator.next());
>                  }
>                  Iterator j = c.iterator();
>                  while (j.hasNext())
>                  {
>                      doDelete(j.next());
>                  }
>         }
> }
> 
> So do you think you could apply this patch - or am I mistaken and I am 
> using OJB in a wrong way?
> 
> With regards
> Tino
> 
> 
> 
> 
> 
> 
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