| package org.apache.commons.ognl.internal; |
| |
| /* |
| * 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. |
| */ |
| |
| /* |
| * $Id$ |
| */ |
| |
| import org.apache.commons.ognl.internal.entry.CacheEntryFactory; |
| |
| import java.util.HashMap; |
| import java.util.Map; |
| import java.util.concurrent.locks.Lock; |
| import java.util.concurrent.locks.ReadWriteLock; |
| import java.util.concurrent.locks.ReentrantReadWriteLock; |
| |
| public class ReentrantReadWriteLockCache<K, V> |
| implements Cache<K, V> |
| { |
| private final ReadWriteLock lock = new ReentrantReadWriteLock(); |
| |
| private final Lock readLock = lock.readLock(); |
| |
| private final Lock writeLock = lock.writeLock(); |
| |
| final Map<K, V> cache = new HashMap<K, V>(); |
| |
| private CacheEntryFactory<K, V> cacheEntryFactory; |
| |
| public ReentrantReadWriteLockCache() |
| { |
| } |
| |
| public ReentrantReadWriteLockCache( CacheEntryFactory<K, V> cacheEntryFactory ) |
| { |
| this.cacheEntryFactory = cacheEntryFactory; |
| } |
| |
| public void clear() |
| { |
| synchronized ( cache ) |
| { |
| cache.clear(); |
| } |
| } |
| |
| public int getSize() |
| { |
| synchronized ( cache ) |
| { |
| return cache.size(); |
| } |
| } |
| |
| |
| public V get( K key ) |
| throws CacheException |
| { |
| V v; |
| boolean shouldCreate; |
| readLock.lock(); |
| try |
| { |
| v = cache.get( key ); |
| shouldCreate = shouldCreate( cacheEntryFactory, v ); |
| } |
| finally |
| { |
| readLock.unlock(); |
| } |
| if ( shouldCreate ) |
| { |
| try |
| { |
| writeLock.lock(); |
| v = cache.get( key ); |
| if ( !shouldCreate( cacheEntryFactory, v ) ) |
| { |
| return v; |
| } |
| v = cacheEntryFactory.create( key ); |
| cache.put( key, v ); |
| return v; |
| } |
| finally |
| { |
| writeLock.unlock(); |
| } |
| |
| } |
| |
| return v; |
| } |
| |
| protected boolean shouldCreate( CacheEntryFactory<K, V> cacheEntryFactory, V v ) |
| throws CacheException |
| { |
| return cacheEntryFactory != null && v == null; |
| } |
| |
| public V put( K key, V value ) |
| { |
| writeLock.lock(); |
| try |
| { |
| cache.put( key, value ); |
| return value; |
| } |
| finally |
| { |
| writeLock.unlock(); |
| } |
| } |
| } |