001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.util;
018
019 import java.io.Serializable;
020 import java.util.Collection;
021 import java.util.Map;
022 import java.util.Set;
023 import java.util.concurrent.atomic.AtomicLong;
024
025 import com.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap;
026 import com.googlecode.concurrentlinkedhashmap.EvictionListener;
027 import org.slf4j.Logger;
028 import org.slf4j.LoggerFactory;
029
030 /**
031 * A Least Recently Used Cache.
032 * <p/>
033 * If this cache stores {@link org.apache.camel.Service} then this implementation will on eviction
034 * invoke the {@link org.apache.camel.Service#stop()} method, to auto-stop the service.
035 *
036 * @see LRUSoftCache
037 * @see LRUWeakCache
038 */
039 public class LRUCache<K, V> implements Map<K, V>, EvictionListener<K, V>, Serializable {
040 private static final long serialVersionUID = -342098639681884414L;
041 private static final Logger LOG = LoggerFactory.getLogger(LRUCache.class);
042
043 private int maxCacheSize = 10000;
044 private boolean stopOnEviction;
045 private final AtomicLong hits = new AtomicLong();
046 private final AtomicLong misses = new AtomicLong();
047 private final AtomicLong evicted = new AtomicLong();
048 private ConcurrentLinkedHashMap<K, V> map;
049
050 /**
051 * Constructs an empty <tt>LRUCache</tt> instance with the
052 * specified maximumCacheSize, and will stop on eviction.
053 *
054 * @param maximumCacheSize the max capacity.
055 * @throws IllegalArgumentException if the initial capacity is negative
056 */
057 public LRUCache(int maximumCacheSize) {
058 this(maximumCacheSize, maximumCacheSize);
059 }
060
061 /**
062 * Constructs an empty <tt>LRUCache</tt> instance with the
063 * specified initial capacity, maximumCacheSize, and will stop on eviction.
064 *
065 * @param initialCapacity the initial capacity.
066 * @param maximumCacheSize the max capacity.
067 * @throws IllegalArgumentException if the initial capacity is negative
068 */
069 public LRUCache(int initialCapacity, int maximumCacheSize) {
070 this(initialCapacity, maximumCacheSize, true);
071 }
072
073 /**
074 * Constructs an empty <tt>LRUCache</tt> instance with the
075 * specified initial capacity, maximumCacheSize,load factor and ordering mode.
076 *
077 * @param initialCapacity the initial capacity.
078 * @param maximumCacheSize the max capacity.
079 * @param stopOnEviction whether to stop service on eviction.
080 * @throws IllegalArgumentException if the initial capacity is negative
081 */
082 public LRUCache(int initialCapacity, int maximumCacheSize, boolean stopOnEviction) {
083 map = new ConcurrentLinkedHashMap.Builder<K, V>()
084 .initialCapacity(initialCapacity)
085 .maximumWeightedCapacity(maximumCacheSize)
086 .listener(this).build();
087 this.maxCacheSize = maximumCacheSize;
088 this.stopOnEviction = stopOnEviction;
089 }
090
091 @Override
092 public V get(Object o) {
093 V answer = map.get(o);
094 if (answer != null) {
095 hits.incrementAndGet();
096 } else {
097 misses.incrementAndGet();
098 }
099 return answer;
100 }
101
102 @Override
103 public int size() {
104 return map.size();
105 }
106
107 @Override
108 public boolean isEmpty() {
109 return map.isEmpty();
110 }
111
112 @Override
113 public boolean containsKey(Object o) {
114 return map.containsKey(o);
115 }
116
117 @Override
118 public boolean containsValue(Object o) {
119 return map.containsValue(0);
120 }
121
122 @Override
123 public V put(K k, V v) {
124 return map.put(k, v);
125 }
126
127 @Override
128 public V remove(Object o) {
129 return map.remove(o);
130 }
131
132 public void putAll(Map<? extends K, ? extends V> map) {
133 this.map.putAll(map);
134 }
135
136 @Override
137 public void clear() {
138 map.clear();
139 resetStatistics();
140 }
141
142 @Override
143 public Set<K> keySet() {
144 return map.ascendingKeySet();
145 }
146
147 @Override
148 public Collection<V> values() {
149 return map.ascendingMap().values();
150 }
151
152 @Override
153 public Set<Entry<K, V>> entrySet() {
154 return map.ascendingMap().entrySet();
155 }
156
157 @Override
158 public void onEviction(K key, V value) {
159 evicted.incrementAndGet();
160 LOG.trace("onEviction {} -> {}", key, value);
161 if (stopOnEviction) {
162 try {
163 // stop service as its evicted from cache
164 ServiceHelper.stopService(value);
165 } catch (Exception e) {
166 LOG.warn("Error stopping service: " + value + ". This exception will be ignored.", e);
167 }
168 }
169 }
170
171 /**
172 * Gets the number of cache hits
173 */
174 public long getHits() {
175 return hits.get();
176 }
177
178 /**
179 * Gets the number of cache misses.
180 */
181 public long getMisses() {
182 return misses.get();
183 }
184
185 /**
186 * Gets the number of evicted entries.
187 */
188 public long getEvicted() {
189 return evicted.get();
190 }
191
192 /**
193 * Returns the maxCacheSize.
194 */
195 public int getMaxCacheSize() {
196 return maxCacheSize;
197 }
198
199 /**
200 * Rest the cache statistics such as hits and misses.
201 */
202 public void resetStatistics() {
203 hits.set(0);
204 misses.set(0);
205 evicted.set(0);
206 }
207
208 @Override
209 public String toString() {
210 return "LRUCache@" + ObjectHelper.getIdentityHashCode(this);
211 }
212 }