| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. 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. For additional information regarding |
| * copyright in this work, please see the NOTICE file in the top level |
| * directory of this distribution. |
| */ |
| |
| package org.apache.roller.weblogger.util.cache; |
| |
| import java.util.Collections; |
| import java.util.Date; |
| import java.util.HashMap; |
| import java.util.LinkedHashMap; |
| import java.util.Map; |
| import org.apache.roller.util.RollerConstants; |
| |
| |
| /** |
| * A simple LRU Cache. |
| */ |
| public class LRUCacheImpl implements Cache { |
| |
| private String id = null; |
| private Map cache = null; |
| |
| // for metrics |
| protected double hits = 0; |
| protected double misses = 0; |
| protected double puts = 0; |
| protected double removes = 0; |
| protected Date startTime = new Date(); |
| |
| |
| protected LRUCacheImpl(String id) { |
| |
| this.id = id; |
| this.cache = Collections.synchronizedMap(new LRULinkedHashMap(100)); |
| } |
| |
| |
| protected LRUCacheImpl(String id, int maxsize) { |
| |
| this.id = id; |
| this.cache = Collections.synchronizedMap(new LRULinkedHashMap(maxsize)); |
| } |
| |
| |
| public String getId() { |
| return this.id; |
| } |
| |
| |
| /** |
| * Store an entry in the cache. |
| */ |
| public synchronized void put(String key, Object value) { |
| |
| this.cache.put(key, value); |
| puts++; |
| } |
| |
| |
| /** |
| * Retrieve an entry from the cache. |
| */ |
| public synchronized Object get(String key) { |
| |
| Object obj = this.cache.get(key); |
| |
| // for metrics |
| if(obj == null) { |
| misses++; |
| } else { |
| hits++; |
| } |
| |
| return obj; |
| } |
| |
| |
| public synchronized void remove(String key) { |
| |
| this.cache.remove(key); |
| removes++; |
| } |
| |
| |
| public synchronized void clear() { |
| |
| this.cache.clear(); |
| |
| // clear metrics |
| hits = 0; |
| misses = 0; |
| puts = 0; |
| removes = 0; |
| startTime = new Date(); |
| } |
| |
| |
| public Map<String, Object> getStats() { |
| |
| Map<String, Object> stats = new HashMap<String, Object>(); |
| stats.put("startTime", this.startTime); |
| stats.put("hits", this.hits); |
| stats.put("misses", this.misses); |
| stats.put("puts", this.puts); |
| stats.put("removes", this.removes); |
| |
| // calculate efficiency |
| if((misses - removes) > 0) { |
| double efficiency = hits / (misses + hits); |
| stats.put("efficiency", efficiency * RollerConstants.PERCENT_100); |
| } |
| |
| return stats; |
| } |
| |
| |
| // David Flanaghan: http://www.davidflanagan.com/blog/000014.html |
| private static class LRULinkedHashMap extends LinkedHashMap { |
| protected int maxsize; |
| |
| public LRULinkedHashMap(int maxsize) { |
| super(maxsize * 4 / 3 + 1, 0.75f, true); |
| this.maxsize = maxsize; |
| } |
| |
| protected boolean removeEldestEntry(Map.Entry eldest) { |
| return this.size() > this.maxsize; |
| } |
| } |
| |
| } |