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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (POOL-284) "Returned object not currently part of this pool" when using mutable objects
Date Mon, 02 Feb 2015 15:43:34 GMT

    [ https://issues.apache.org/jira/browse/POOL-284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14301382#comment-14301382
] 

Phil Steitz commented on POOL-284:
----------------------------------

An alternative to 3. above that may be a little cheaper:  just make allObjects use Integer
keys and wrap gets/puts in System.identityHashCode calls.

> "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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