| package org.apache.commons.jcs3.engine.memory.lru; |
| |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| import java.io.IOException; |
| import java.util.Collections; |
| import java.util.Map; |
| |
| import org.apache.commons.jcs3.engine.behavior.ICacheElement; |
| import org.apache.commons.jcs3.engine.control.CompositeCache; |
| import org.apache.commons.jcs3.engine.memory.AbstractMemoryCache; |
| import org.apache.commons.jcs3.engine.memory.util.MemoryElementDescriptor; |
| import org.apache.commons.jcs3.engine.stats.behavior.IStats; |
| import org.apache.commons.jcs3.log.Log; |
| import org.apache.commons.jcs3.log.LogManager; |
| |
| /** |
| * This is a test memory manager using the jdk1.4 LinkedHashMap. |
| */ |
| public class LHMLRUMemoryCache<K, V> |
| extends AbstractMemoryCache<K, V> |
| { |
| /** The Logger. */ |
| private static final Log log = LogManager.getLog( LRUMemoryCache.class ); |
| |
| /** |
| * For post reflection creation initialization |
| * <p> |
| * @param hub |
| */ |
| @Override |
| public void initialize( CompositeCache<K, V> hub ) |
| { |
| super.initialize( hub ); |
| log.info( "initialized LHMLRUMemoryCache for {0}", () -> getCacheName() ); |
| } |
| |
| /** |
| * Returns a synchronized LHMSpooler |
| * <p> |
| * @return Collections.synchronizedMap( new LHMSpooler() ) |
| */ |
| @Override |
| public Map<K, MemoryElementDescriptor<K, V>> createMap() |
| { |
| return Collections.synchronizedMap( new LHMSpooler() ); |
| } |
| |
| /** |
| * Puts an item to the cache. |
| * <p> |
| * @param ce Description of the Parameter |
| * @throws IOException |
| */ |
| @Override |
| public void update( ICacheElement<K, V> ce ) |
| throws IOException |
| { |
| putCnt.incrementAndGet(); |
| map.put( ce.getKey(), new MemoryElementDescriptor<>(ce) ); |
| } |
| |
| /** |
| * Update control structures after get |
| * (guarded by the lock) |
| * |
| * @param me the memory element descriptor |
| */ |
| @Override |
| protected void lockedGetElement(MemoryElementDescriptor<K, V> me) |
| { |
| // empty |
| } |
| |
| /** |
| * Remove element from control structure |
| * (guarded by the lock) |
| * |
| * @param me the memory element descriptor |
| */ |
| @Override |
| protected void lockedRemoveElement(MemoryElementDescriptor<K, V> me) |
| { |
| // empty |
| } |
| |
| /** |
| * Removes all cached items from the cache control structures. |
| * (guarded by the lock) |
| */ |
| @Override |
| protected void lockedRemoveAll() |
| { |
| // empty |
| } |
| |
| /** |
| * This returns semi-structured information on the memory cache, such as the size, put count, |
| * hit count, and miss count. |
| * <p> |
| * @return IStats |
| */ |
| @Override |
| public IStats getStatistics() |
| { |
| IStats stats = super.getStatistics(); |
| stats.setTypeName( "LHMLRU Memory Cache" ); |
| |
| return stats; |
| } |
| |
| // ---------------------------------------------------------- debug methods |
| |
| /** |
| * Dump the cache entries from first to last for debugging. |
| */ |
| public void dumpCacheEntries() |
| { |
| dumpMap(); |
| } |
| |
| /** |
| * This can't be implemented. |
| * <p> |
| * @param numberToFree |
| * @return 0 |
| * @throws IOException |
| */ |
| @Override |
| public int freeElements( int numberToFree ) |
| throws IOException |
| { |
| // can't be implemented using the LHM |
| return 0; |
| } |
| |
| // ---------------------------------------------------------- extended map |
| |
| /** |
| * Implementation of removeEldestEntry in LinkedHashMap |
| */ |
| protected class LHMSpooler |
| extends java.util.LinkedHashMap<K, MemoryElementDescriptor<K, V>> |
| { |
| /** Don't change. */ |
| private static final long serialVersionUID = -1255907868906762484L; |
| |
| /** |
| * Initialize to a small size--for now, 1/2 of max 3rd variable "true" indicates that it |
| * should be access and not time governed. This could be configurable. |
| */ |
| public LHMSpooler() |
| { |
| super( (int) ( getCacheAttributes().getMaxObjects() * .5 ), .75F, true ); |
| } |
| |
| /** |
| * Remove eldest. Automatically called by LinkedHashMap. |
| * <p> |
| * @param eldest |
| * @return true if removed |
| */ |
| @SuppressWarnings("synthetic-access") |
| @Override |
| protected boolean removeEldestEntry( Map.Entry<K, MemoryElementDescriptor<K, V>> eldest ) |
| { |
| ICacheElement<K, V> element = eldest.getValue().getCacheElement(); |
| |
| if ( size() <= getCacheAttributes().getMaxObjects() ) |
| { |
| return false; |
| } |
| else |
| { |
| log.debug( "LHMLRU max size: {0}. Spooling element, key: {1}", |
| () -> getCacheAttributes().getMaxObjects(), () -> element.getKey() ); |
| |
| waterfal( element ); |
| |
| log.debug( "LHMLRU size: {0}", () -> map.size() ); |
| } |
| return true; |
| } |
| } |
| } |