openwfe.org.misc.Cache Maven / Gradle / Ivy
/*
* Copyright (c) 2001-2006, John Mettraux, OpenWFE.org
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* . Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* . Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* . Neither the name of the "OpenWFE" nor the names of its contributors may be
* used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* $Id: Cache.java 3451 2006-10-08 13:19:33Z jmettraux $
*/
//
// Cache.java
//
// [email protected]
//
// generated with
// jtmpl 1.0.04 20.11.2001 John Mettraux ([email protected])
//
package openwfe.org.misc;
import openwfe.org.xml.XmlUtils;
/**
* A cache implementation : it's in fact a map with a max capacity.
* When you put an item in a cache that is full, the least recently used item
* will be thrown out to give its place to the incoming item.
*
* CVS Info :
*
$Author: jmettraux $
*
$Date: 2006-10-08 22:19:33 +0900 (Sun, 08 Oct 2006) $
*
$Id: Cache.java 3451 2006-10-08 13:19:33Z jmettraux $
*
* @author [email protected]
*/
public class Cache
{
/*
private final static org.apache.log4j.Logger log = org.apache.log4j.Logger
.getLogger(Cache.class.getName());
*/
//
// FIELDS
private int maxSize = -1;
private LruMap cache = null;
//
// CONSTRUCTORS
/**
* Builds a cache with a custom maxSize.
*/
public Cache (final int maxSize)
{
super();
this.maxSize = maxSize;
if (maxSize < 1)
{
throw new IllegalArgumentException
("Cannot build a cache with a maxSize < 1 : "+maxSize);
}
this.cache = new LruMap(maxSize);
}
/**
* Builds a cache with the default capacity (maxSize set to 100).
*/
public Cache ()
{
this(100);
}
//
// METHODS
/**
* Like the get() method of a Map.
*/
public synchronized Object get (final Object key)
{
return this.cache.get(key);
}
/**
* Like the remove() method of a Map.
*/
public synchronized Object remove (final Object key)
{
return this.cache.remove(key);
}
/**
* Like the put() method of a Map.
*/
public synchronized void put (final Object key, final Object value)
{
this.cache.put(key, value);
}
/**
* Returns the count of items currently stored in this cache.
*/
public int size ()
{
return this.cache.size();
}
/**
* Returns the capacity attributed to this cache.
*/
public int maxSize ()
{
return this.maxSize;
}
/**
* Beware : you have to handle sync by yourself
*/
public java.util.Iterator iterator ()
{
return this.cache.values().iterator();
}
/**
* Like the keySet() method of a Map.
*/
public java.util.Set keySet ()
{
return this.cache.keySet();
}
/**
* Like the entrySet() method of a Map.
*/
public java.util.Set entrySet ()
{
return this.cache.entrySet();
}
/**
* Like the values() method of a Map.
*/
public java.util.Collection values ()
{
return this.cache.values();
}
/**
* This method is used by the getStatus() method of services
* using a cache
*/
public org.jdom.Element getStatus ()
{
org.jdom.Element cacheElt = new org.jdom.Element("cache");
cacheElt.addContent(XmlUtils.getRevisionElt("$Id: Cache.java 3451 2006-10-08 13:19:33Z jmettraux $"));
java.util.Iterator it = this.cache.keySet().iterator();
while (it.hasNext())
{
org.jdom.Element keyElt = new org.jdom.Element("key");
keyElt.addContent(it.next().toString());
cacheElt.addContent(keyElt);
}
return cacheElt;
}
//
// INNER CLASSES
private static class LruMap
extends java.util.LinkedHashMap
{
private int capacity = -1;
public LruMap (final int capacity)
{
super(capacity, 0.75f, true);
//
// setting accessOrder to true (LRU)
this.capacity = capacity;
}
protected boolean removeEldestEntry (final java.util.Map.Entry eldest)
{
return (this.size() > this.capacity);
}
}
}