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.util.function.Supplier;
22
23 /**
24 * A container for data that is specific to a repository system session. Both components within the repository system
25 * and clients of the system may use this storage to associate arbitrary data with a session.
26 * <p>
27 * Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be
28 * abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion.
29 * <p>
30 * <strong>Note:</strong> Actual implementations must be thread-safe.
31 *
32 * @see RepositorySystemSession#getData()
33 * @noimplement This interface is not intended to be implemented by clients.
34 * @noextend This interface is not intended to be extended by clients.
35 */
36 public interface SessionData {
37
38 /**
39 * Associates the specified session data with the given key.
40 *
41 * @param key The key under which to store the session data, must not be {@code null}.
42 * @param value The data to associate with the key, may be {@code null} to remove the mapping.
43 */
44 void set(Object key, Object value);
45
46 /**
47 * Associates the specified session data with the given key if the key is currently mapped to the given value. This
48 * method provides an atomic compare-and-update of some key's value.
49 *
50 * @param key The key under which to store the session data, must not be {@code null}.
51 * @param oldValue The expected data currently associated with the key, may be {@code null}.
52 * @param newValue The data to associate with the key, may be {@code null} to remove the mapping.
53 * @return {@code true} if the key mapping was successfully updated from the old value to the new value,
54 * {@code false} if the current key mapping didn't match the expected value and was not updated.
55 */
56 boolean set(Object key, Object oldValue, Object newValue);
57
58 /**
59 * Gets the session data associated with the specified key.
60 *
61 * @param key The key for which to retrieve the session data, must not be {@code null}.
62 * @return The session data associated with the key or {@code null} if none.
63 */
64 Object get(Object key);
65
66 /**
67 * Retrieve of compute the data associated with the specified key.
68 *
69 * @param key The key for which to retrieve the session data, must not be {@code null}.
70 * @param supplier The supplier will compute the new value.
71 * @return The session data associated with the key.
72 */
73 Object computeIfAbsent(Object key, Supplier<Object> supplier);
74 }