| 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 }