Mega Code Archive
Map implementation for cache usage
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/*
* This file is part of aion-emu <aion-emu.com>.
*
* aion-emu is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* aion-emu 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with aion-emu. If not, see <http://www.gnu.org/licenses/>.
*/
//package com.aionemu.gameserver.utils.collections.cachemap;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.Map;
/**
* This class is a simple map implementation for cache usage.<br>
* <br>
* Value may be stored in map really long, but it for sure will be removed if there is low memory (and of course there
* isn't any strong reference to value object)
*
* @author Luno
*/
class SoftCacheMap<K, V> extends AbstractCacheMap<K, V> implements CacheMap<K, V>
{
/**
* This class is a {@link SoftReference} with additional responsibility of holding key object
*
* @author Luno
*/
private class SoftEntry extends SoftReference<V>
{
private K key;
SoftEntry(K key, V referent, ReferenceQueue<? super V> q)
{
super(referent, q);
this.key = key;
}
K getKey()
{
return key;
}
}
SoftCacheMap(String cacheName, String valueName)
{
super(cacheName, valueName);
}
@SuppressWarnings("unchecked")
@Override
protected synchronized void cleanQueue()
{
SoftEntry en = null;
while ((en = (SoftEntry) refQueue.poll()) != null)
{
K key = en.getKey();
cacheMap.remove(key);
}
}
@Override
protected Reference<V> newReference(K key, V value, ReferenceQueue<V> vReferenceQueue)
{
return new SoftEntry(key, value, vReferenceQueue);
}
}
/**
* Base class for {@link WeakCacheMap} and {@link SoftCacheMap}
*
* @author Luno
*
* @param <K>
* @param <V>
*/
abstract class AbstractCacheMap<K, V> implements CacheMap<K, V>
{
protected final String cacheName;
protected final String valueName;
/** Map storing references to cached objects */
protected final Map<K, Reference<V>> cacheMap = new HashMap<K, Reference<V>>();
protected final ReferenceQueue<V> refQueue = new ReferenceQueue<V>();
/**
* @param cacheName
* @param valueName
*/
AbstractCacheMap(String cacheName, String valueName)
{
this.cacheName = "#CACHE [" + cacheName + "]# ";
this.valueName = valueName;
}
/** {@inheritDoc} */
@Override
public void put(K key, V value)
{
cleanQueue();
if (cacheMap.containsKey(key))
throw new IllegalArgumentException("Key: " + key + " already exists in map");
Reference<V> entry = newReference(key, value, refQueue);
cacheMap.put(key, entry);
}
/** {@inheritDoc} */
@Override
public V get(K key)
{
cleanQueue();
Reference<V> reference = cacheMap.get(key);
if (reference == null)
return null;
V res = reference.get();
return res;
}
@Override
public boolean contains(K key)
{
cleanQueue();
return cacheMap.containsKey(key);
}
protected abstract void cleanQueue();
@Override
public void remove(K key)
{
cacheMap.remove(key);
}
protected abstract Reference<V> newReference(K key, V value, ReferenceQueue<V> queue);
}
interface CacheMap<K, V>
{
/**
* Adds a pair <key,value> to cache map.<br>
* <br>
*
* <font color='red'><b>NOTICE:</b> </font> if there is already a value with given id in the map,
* {@link IllegalArgumentException} will be thrown.
*
* @param key
* @param value
*/
public void put(K key, V value);
/**
* Returns cached value correlated to given key.
*
* @param key
* @return V
*/
public V get(K key);
/**
* Checks whether this map contains a value related to given key.
* @param key
* @return true or false
*/
public boolean contains(K key);
/**
* Removes an entry from the map, that has given key.
* @param key
*/
public void remove(K key);
}
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