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.apache.maven.api;
20
21 import java.util.function.Supplier;
22 import org.apache.maven.api.annotations.Experimental;
23 import org.apache.maven.api.annotations.Nonnull;
24 import org.apache.maven.api.annotations.Nullable;
25 import org.apache.maven.api.annotations.Provider;
26 import org.apache.maven.api.annotations.ThreadSafe;
27
28 /**
29 * A container for data that is specific to a session.
30 * All components may use this storage to associate arbitrary data with a session.
31 * <p>
32 * Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be
33 * abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion.
34 * <p>
35 * <strong>Note:</strong> Actual implementations must be thread-safe.
36 *
37 * @see Session#getData()
38 * @since 4.0
39 */
40 @Experimental
41 @ThreadSafe
42 @Provider
43 public interface SessionData {
44
45 /**
46 * Associates the specified session data with the given key.
47 *
48 * @param key the key under which to store the session data, must not be {@code null}
49 * @param value the data to associate with the key, may be {@code null} to remove the mapping
50 */
51 void set(@Nonnull Object key, @Nullable Object value);
52
53 /**
54 * Associates the specified session data with the given key if the key is currently mapped to the given value. This
55 * method provides an atomic compare-and-update of some key's value.
56 *
57 * @param key the key under which to store the session data, must not be {@code null}
58 * @param oldValue the expected data currently associated with the key, may be {@code null}
59 * @param newValue the data to associate with the key, may be {@code null} to remove the mapping
60 * @return {@code true} if the key mapping was successfully updated from the old value to the new value,
61 * {@code false} if the current key mapping didn't match the expected value and was not updated.
62 */
63 boolean set(@Nonnull Object key, @Nullable Object oldValue, @Nullable Object newValue);
64
65 /**
66 * Gets the session data associated with the specified key.
67 *
68 * @param key the key for which to retrieve the session data, must not be {@code null}
69 * @return the session data associated with the key or {@code null} if none
70 */
71 @Nullable
72 Object get(@Nonnull Object key);
73
74 /**
75 * Retrieve of compute the data associated with the specified key.
76 *
77 * @param key the key for which to retrieve the session data, must not be {@code null}
78 * @param supplier the supplier will compute the new value
79 * @return the session data associated with the key
80 */
81 @Nullable
82 Object computeIfAbsent(@Nonnull Object key, @Nonnull Supplier<Object> supplier);
83 }