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;
20
21 import java.io.Closeable;
22 import java.util.Collection;
23
24 import org.eclipse.aether.artifact.Artifact;
25 import org.eclipse.aether.metadata.Metadata;
26
27 /**
28 * A synchronization context used to coordinate concurrent access to artifacts or metadatas. The typical usage of a
29 * synchronization context looks like this:
30 *
31 * <pre>
32 * SyncContext syncContext = repositorySystem.newSyncContext( ... );
33 * try {
34 * syncContext.acquire( artifacts, metadatas );
35 * // work with the artifacts and metadatas
36 * } finally {
37 * syncContext.close();
38 * }
39 * </pre>
40 *
41 * Within one thread, synchronization contexts may be nested which can naturally happen in a hierarchy of method calls.
42 * The nested synchronization contexts may also acquire overlapping sets of artifacts/metadatas as long as the following
43 * conditions are met. If the outer-most context holding a particular resource is exclusive, that resource can be
44 * reacquired in any nested context. If however the outer-most context is shared, the resource may only be reacquired by
45 * nested contexts if these are also shared.
46 * <p>
47 * A synchronization context is meant to be utilized by only one thread and as such is not thread-safe.
48 * <p>
49 * Note that the level of actual synchronization is subject to the implementation and might range from OS-wide to none.
50 *
51 * @see RepositorySystem#newSyncContext(RepositorySystemSession, boolean)
52 */
53 public interface SyncContext extends Closeable {
54
55 /**
56 * Acquires synchronized access to the specified artifacts and metadatas. The invocation will potentially block
57 * until all requested resources can be acquired by the calling thread. Acquiring resources that are already
58 * acquired by this synchronization context has no effect. Please also see the class-level documentation for
59 * information regarding reentrancy. The method may be invoked multiple times on a synchronization context until all
60 * desired resources have been acquired.
61 *
62 * @param artifacts The artifacts to acquire, may be {@code null} or empty if none.
63 * @param metadatas The metadatas to acquire, may be {@code null} or empty if none.
64 * @throws FailedToAcquireLockException if method calls to acquire lock within configured time.
65 */
66 void acquire(Collection<? extends Artifact> artifacts, Collection<? extends Metadata> metadatas)
67 throws FailedToAcquireLockException;
68
69 /**
70 * Releases all previously acquired artifacts/metadatas. If no resources have been acquired before or if this
71 * synchronization context has already been closed, this method does nothing.
72 */
73 @Override
74 void close();
75
76 /**
77 * Specific exception thrown by {@link #acquire(Collection, Collection)} method when it cannot acquire the lock.
78 *
79 * @since 1.9.25
80 */
81 final class FailedToAcquireLockException extends IllegalStateException {
82 private final boolean shared;
83
84 /**
85 * Constructor.
86 */
87 public FailedToAcquireLockException(boolean shared, String message) {
88 super(message);
89 this.shared = shared;
90 }
91
92 /**
93 * Returns {@code true} for shared and {@code false} for exclusive sync contexts.
94 */
95 public boolean isShared() {
96 return shared;
97 }
98 }
99 }