1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.eclipse.aether.named;
20
21 import java.util.concurrent.TimeUnit;
22
23 /**
24 * A named lock, functionally similar to existing JVM and other implementations. Must support boxing (reentrancy), but
25 * no lock upgrade is supported. The lock instance obtained from lock factory must be treated as a resource, best in
26 * try-with-resource block. Usual pattern to use this lock:
27 * <pre>
28 * try (NamedLock lock = factory.getLock("resourceName")) {
29 * if (lock.lockExclusively(10L, Timeunit.SECONDS)) {
30 * try {
31 * ... exclusive access to "resourceName" resource gained here
32 * }
33 * finally {
34 * lock.unlock();
35 * }
36 * }
37 * else {
38 * ... failed to gain access within specified time, handle it
39 * }
40 * }
41 * </pre>
42 */
43 public interface NamedLock extends AutoCloseable {
44 /**
45 * Returns this instance key, never {@code null}.
46 */
47 NamedLockKey key();
48
49 /**
50 * Tries to lock shared, may block for given time. If successful, returns {@code true}.
51 */
52 boolean lockShared(long time, TimeUnit unit) throws InterruptedException;
53
54 /**
55 * Tries to lock exclusively, may block for given time. If successful, returns {@code true}.
56 */
57 boolean lockExclusively(long time, TimeUnit unit) throws InterruptedException;
58
59 /**
60 * Unlocks the lock, must be invoked by caller after one of the {@link #lockShared(long, TimeUnit)} or {@link
61 * #lockExclusively(long, TimeUnit)}.
62 */
63 void unlock();
64
65 /**
66 * Closes the lock resource. Lock MUST be unlocked using {@link #unlock()} in case any locking happened on it. After
67 * invoking this method, the lock instance MUST NOT be used anymore. If lock for same name needed, a new instance
68 * should be obtained from factory using {@link NamedLockFactory#getLock(java.util.Collection)}. Ideally,
69 * instances are to be used within try-with-resource blocks, so calling this method directly is not really
70 * needed, nor advised.
71 */
72 @Override
73 void close();
74 }