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https://issues.apache.org/jira/browse/POOL-284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14307879#comment-14307879
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Thomas Neidhart commented on POOL-284:
--------------------------------------
Another idea would be to use a modified StaticBucketMap from collections that
uses System.identityHashCode and reference comparison for equality checks.
> "Returned object not currently part of this pool" when using mutable objects
> ----------------------------------------------------------------------------
>
> Key: POOL-284
> URL: https://issues.apache.org/jira/browse/POOL-284
> Project: Commons Pool
> Issue Type: Bug
> Affects Versions: 2.2
> Reporter: Valentin Mayamsin
>
> I'm using pool to reuse expensive Sets (storing millions of items). Here is a
> test which fails:
> {code}
> GenericObjectPoolConfig config = new GenericObjectPoolConfig ();
> GenericObjectPool<Set> aPool = new GenericObjectPool<> ( new
> BasePooledObjectFactory<Set> ()
> {
> @Override
> public Set create () throws Exception
> {
> return new HashSet();
> }
> @Override
> public PooledObject<Set> wrap ( Set o )
> {
> return new DefaultPooledObject<> ( o );
> }
> @Override
> public void passivateObject ( PooledObject<Set> p ) throws
> Exception
> {
> p.getObject ().clear ();
> super.passivateObject ( p );
> }
> }, config );
> Set set = aPool.borrowObject ();
> set.add ( new Object () );
>
> aPool.returnObject ( set );
> {code}
> This is because GenericObjectPool uses a HashMap<Object, PooledObject> to
> correlate objects and state. HashMap stores objects correlated to their
> hashCode. So in case object's state change then hashCode will change, thus
> Map will fail to correlate this object since it stores old hashCode
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