com.mchange.util.impl.SoftReferenceObjectCache Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java v.0.2.3
*
* Copyright (C) 2012 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* 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.util.impl;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.Map;
import com.mchange.util.ObjectCache;
public abstract class SoftReferenceObjectCache implements ObjectCache
{
Map store = new HashMap();
public synchronized Object find(Object key) throws Exception
{
Reference ref = (Reference) store.get(key);
Object out;
if (ref == null || (out = ref.get()) == null || isDirty(key, out))
{
out = createFromKey(key);
store.put(key, new SoftReference(out));
}
return out;
}
protected boolean isDirty(Object key, Object cached)
{return false;}
protected abstract Object createFromKey(Object key) throws Exception;
}