[kepler-dev] change proposal for ptolemy.vergil.tree.EntityTreeModel class.

[Jianwu Wang]

  Hi Christopher,

     Since WeakReference.get() could return null, we'd better check it 
after using this function. So I changed this class a little big more. 
Please find new class from the attachment and check it in if you think 
it is proper. Thanks.

On 9/20/10 6:14 PM, Christopher Brooks wrote:
> Hi Jianwu,
>
> Your change looks ok to me.  The diff between what you sent and what
> is in the tree is below:
>
> bash-3.2$ diff ~/Downloads/EntityTreeModelNew.java EntityTreeModel.java
> 30d29
> < import java.lang.ref.WeakReference;
> 64c63
> < public class EntityTreeModelNew implements TreeModel {
> ---
> > public class EntityTreeModel implements TreeModel {
> 70c69
> <     public EntityTreeModelNew(NamedObj root) {
> ---
> >     public EntityTreeModel(NamedObj root) {
> 82c81
> <         _listenerList.add(new WeakReference(listener));
> ---
> >         _listenerList.add(listener);
> 176c175
> <         _listenerList.remove(new WeakReference(listener));
> ---
> >         _listenerList.remove(listener);
> 188c187
> <             TreeModelListener listener = (TreeModelListener) 
> ((WeakReference)listeners.next()).get();
> ---
> >             TreeModelListener listener = (TreeModelListener) 
> listeners.next();
> 263c262
> <     private List _listenerList = new LinkedList<WeakReference>();
> ---
> >     private List _listenerList = new LinkedList();
>
>
> I folded in the change and added a comment:
>
>   /** Add a listener to this model.
>      *  @param listener The listener to add.
>      *  @see #removeTreeModelListener(TreeModelListener)
>      */
>     public void addTreeModelListener(TreeModelListener listener) {
>         // In http://bugzilla.ecoinformatics.org/show_bug.cgi?id=4801,
>         // Jianwu Wang found that the _listenerList attribute in
>         // ptolemy.vergil.tree.EntityTreeModel was leaking memory.
>         // This attribute keeps holding some references, so that
>         // instances of EntityTreeModel and its sub-classes can not be
>         // GCed when a window is open and closed.
>         //
>         // When it and its sub-classes are used in Kepler,
>         // addTreeModelListener() and removeTreeModelListener()
>         // functions of EntityTreeModel class are called implicitly.
>         // Jianwu did not find a good way to clean up after a window
>         // is closed.  Changing the _listenerList attribute using
>         // WeakReference fixe the leak.
>         _listenerList.add(new WeakReference(listener));
>     }
>
> I updated the 8.0 release branch, thanks for the patch!
>
> Derik, I think you would want this in the 2.1 release.  I'm still 
> working on deterimining
> if ptolemy-8.0.0 is what should be shipped with Kepler 2.1.
>
> _Christopher
>
>
> On 9/20/10 4:27 PM, Jianwu Wang wrote:
>> As I mentioned at 
>> http://bugzilla.ecoinformatics.org/show_bug.cgi?id=4801, I found one 
>> class might need to be changed for memory leak.  It's the 
>> _listenerList attribute in
>> ptolemy.vergil.tree.EntityTreeModel. One memory leak I'm tracing down 
>> is that this attribute keeps holding some references, so that 
>> instances of EntityTreeModel and its sub-classes can not be GCed
>> when a window is open and closed.
>>
>>     When it and its sub-classes are used in Kepler,  
>> addTreeModelListener() and removeTreeModelListener() functions of 
>> EntityTreeModel class are called implicitly.  I haven't find good 
>> ways to clean
>> up after a window is closed.
>>
>>     If changing the  _listenerList attribute using WeakReference, it 
>> will be able to fix the leak.
>


-- 

Best wishes

Sincerely yours

Jianwu Wang
jianwu at sdsc.edu

Assistant Project Scientist
Scientific Workflow Automation Technologies (SWAT) Laboratory
San Diego Supercomputer Center
University of California, San Diego
San Diego, U.S.A.

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