abstractweakcoalescer.java

c3p0数据库连接池实现源码

/*
 * Distributed as part of c3p0 v.0.9.1-pre6
 *
 * Copyright (C) 2005 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <[e-mail]>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1, as 
 * published by the Free Software Foundation.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this software; see the file LICENSE.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */


package com.mchange.v2.coalesce;

import java.util.*;
import java.lang.ref.WeakReference;

class AbstractWeakCoalescer implements Coalescer
{
    Map wcoalesced;

    AbstractWeakCoalescer( Map wcoalesced )
    { this.wcoalesced = wcoalesced; }

    public Object coalesce( Object o )
    {
	//System.err.println("AbstractWeakCoalescer.coalesce( " + o + " )");
	Object out = null;

	WeakReference wr = (WeakReference) wcoalesced.get( o );
	if ( wr != null ) 
	    out = wr.get(); //there is a conceivable race that would
    	                    //permit wr be cleared
	if ( out == null )
	    {
		wcoalesced.put( o , new WeakReference(o) );
		out = o;
	    }
	return out;
    }

    public int countCoalesced()
    { return wcoalesced.size(); }

    public Iterator iterator()
    { return new CoalescerIterator( wcoalesced.keySet().iterator() ); }
}