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From "Valentin Mayamsin (JIRA)" <j...@apache.org>
Subject [jira] [Created] (POOL-284) "Returned object not currently part of this pool" when using mutable objects
Date Tue, 27 Jan 2015 23:54:34 GMT
Valentin Mayamsin created POOL-284:
--------------------------------------

             Summary: "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 Sets.newHashSet ();
            }

            @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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