ReadWriteLockRegistry.java |
1 /** 2 * Copyright (c) 2000-2009 Liferay, Inc. All rights reserved. 3 * 4 * 5 * 6 * 7 * The contents of this file are subject to the terms of the Liferay Enterprise 8 * Subscription License ("License"). You may not use this file except in 9 * compliance with the License. You can obtain a copy of the License by 10 * contacting Liferay, Inc. See the License for the specific language governing 11 * permissions and limitations under the License, including but not limited to 12 * distribution rights of the Software. 13 * 14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 20 * SOFTWARE. 21 */ 22 23 package com.liferay.portal.kernel.concurrent; 24 25 import java.util.concurrent.ConcurrentHashMap; 26 import java.util.concurrent.ConcurrentMap; 27 import java.util.concurrent.locks.Lock; 28 import java.util.concurrent.locks.ReadWriteLock; 29 import java.util.concurrent.locks.ReentrantReadWriteLock; 30 31 /** 32 * <a href="ReadWriteLockRegistry.java.html"><b><i>View Source</i></b></a> 33 * 34 * Registry for {@link ReadWriteLock} objects with {@link ReadWriteLockKey} as 35 * keys. The behavior of acquiring and releasing locks is provided by a {@link 36 * ConcurrentHashMap}. This class is completely thread safe and ensures that 37 * only one {@link ReadWriteLock} exists per key. <a 38 * href="ReadWriteLockRegistry.java.html"><b><i>View Source</i></b></a> 39 * 40 * @author Shuyang Zhou 41 * @see ReadWriteLock 42 * @see ReadWriteLockKey 43 */ 44 public class ReadWriteLockRegistry { 45 46 public Lock acquireLock(ReadWriteLockKey<?> readWriteLockKey) { 47 ReadWriteLock readWriteLock = _readWriteLockMap.get(readWriteLockKey); 48 49 if (readWriteLock == null) { 50 ReadWriteLock newReadWriteLock = new ReentrantReadWriteLock(); 51 52 readWriteLock = _readWriteLockMap.putIfAbsent( 53 readWriteLockKey, newReadWriteLock); 54 55 if (readWriteLock == null) { 56 readWriteLock = newReadWriteLock; 57 } 58 } 59 60 if (readWriteLockKey.isWriteLock()) { 61 return readWriteLock.writeLock(); 62 } 63 else { 64 return readWriteLock.readLock(); 65 } 66 } 67 68 public void releaseLock(ReadWriteLockKey<?> readWriteLockKey) { 69 if (readWriteLockKey.isWriteLock()) { 70 _readWriteLockMap.remove(readWriteLockKey); 71 } 72 } 73 74 private ConcurrentMap<ReadWriteLockKey<?>, ReadWriteLock> 75 _readWriteLockMap = new ConcurrentHashMap 76 <ReadWriteLockKey<?>, ReadWriteLock>(); 77 78 }