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From Kevin Zhou <zhoukevi...@gmail.com>
Subject Re: [jira] Commented: (HARMONY-6009) [classlib][beans] NPE launching swingset2 example
Date Wed, 19 Nov 2008 10:13:11 GMT
Tim Ellison wrote:
> Hi Kevin,
> Kevin Zhou wrote:
>> I think this defect may be a thread-safe problem.
>> I read HARMONY's PropertyChangeSupport code and found that:
>> It employs ArrayList to store the property change listeners which is not
>> thread-safe.
>> This defect occurs in a private doFirePropertyChange method.
>> This method may asynchronously use the list of PropertyChangeListener, which
>> contains a null value when modification (add or remove) of the list has not
>> finished.
> Yes, I put in some trace code and there is a null stored in the
> globalListeners list which causes the NPE.
> However, I don't see where that null could have been stored.  Can you
> suggest what part of the code has stored the null in there?  Every add
> to the list first checks for null.  I'll take a look and see if I can
> catch it in the test.
> I won't apply your 'check-for-null' patch since I think that just masks
> the underlying problem.
> Regards,
> Tim
Hi Tim,
This patch doesn't only check-for-null.
It also changes the private doFirePropertyChange method to synchronized 
method. This may resolve the asynchronous operation on globalListeners list.
I will try to find what part of the code has stored the null.
Due to license cares, I think it difficult to find the setting-null code 
which may be inside SwingSet2.jar.
Will manage to handle this.
Kevin Zhou

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