com.mchange.util.impl.SoftReferenceObjectCache Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java 0.2.6.3
*
* Copyright (C) 2013 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of EITHER:
*
* 1) The GNU Lesser General Public License (LGPL), version 2.1, as
* published by the Free Software Foundation
*
* OR
*
* 2) The Eclipse Public License (EPL), version 1.0
*
* You may choose which license to accept if you wish to redistribute
* or modify this work. You may offer derivatives of this work
* under the license you have chosen, or you may provide the same
* choice of license which you have been offered here.
*
* 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.
*
* You should have received copies of both LGPL v2.1 and EPL v1.0
* along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
* If not, the text of these licenses are currently available at
*
* LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php
*
*/
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;
}