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 23 import org.apache.maven.api.annotations.Experimental; 24 import org.apache.maven.api.annotations.Nonnull; 25 import org.apache.maven.api.annotations.Nullable; 26 import org.apache.maven.api.annotations.Provider; 27 import org.apache.maven.api.annotations.ThreadSafe; 28 29 /** 30 * A container for data that is specific to a session. 31 * All components may use this storage to associate arbitrary data with a session. 32 * <p> 33 * Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be 34 * abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion. 35 * <p> 36 * <strong>Note:</strong> Actual implementations must be thread-safe. 37 * 38 * @see Session#getData() 39 * @since 4.0 40 */ 41 @Experimental 42 @ThreadSafe 43 @Provider 44 public interface SessionData { 45 46 /** 47 * Associates the specified session data with the given key. 48 * 49 * @param key the key under which to store the session data, must not be {@code null} 50 * @param value the data to associate with the key, may be {@code null} to remove the mapping 51 */ 52 void set(@Nonnull Object key, @Nullable Object value); 53 54 /** 55 * Associates the specified session data with the given key if the key is currently mapped to the given value. This 56 * method provides an atomic compare-and-update of some key's value. 57 * 58 * @param key the key under which to store the session data, must not be {@code null} 59 * @param oldValue the expected data currently associated with the key, may be {@code null} 60 * @param newValue the data to associate with the key, may be {@code null} to remove the mapping 61 * @return {@code true} if the key mapping was successfully updated from the old value to the new value, 62 * {@code false} if the current key mapping didn't match the expected value and was not updated. 63 */ 64 boolean set(@Nonnull Object key, @Nullable Object oldValue, @Nullable Object newValue); 65 66 /** 67 * Gets the session 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 * @return the session data associated with the key or {@code null} if none 71 */ 72 @Nullable 73 Object get(@Nonnull Object key); 74 75 /** 76 * Retrieve of compute the data associated with the specified key. 77 * 78 * @param key the key for which to retrieve the session data, must not be {@code null} 79 * @param supplier the supplier will compute the new value 80 * @return the session data associated with the key 81 */ 82 @Nullable 83 Object computeIfAbsent(@Nonnull Object key, @Nonnull Supplier<Object> supplier); 84 }