| // *************************************************************************************************************************** |
| // * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file * |
| // * distributed with this work for additional information regarding copyright ownership. The ASF licenses this file * |
| // * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance * |
| // * with the License. You may obtain a copy of the License at * |
| // * * |
| // * http://www.apache.org/licenses/LICENSE-2.0 * |
| // * * |
| // * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an * |
| // * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * |
| // * specific language governing permissions and limitations under the License. * |
| // *************************************************************************************************************************** |
| package org.apache.juneau.internal; |
| |
| import java.util.concurrent.*; |
| |
| /** |
| * Simple in-memory cache of objects. |
| * |
| * <p> |
| * Essentially just a wrapper around a ConcurrentHashMap. |
| * |
| * @param <K> The key type. |
| * @param <V> The value type. |
| */ |
| public class Cache<K,V> { |
| private final boolean nocache; |
| private final int maxSize; |
| private final ConcurrentHashMap<K,V> cache; |
| |
| /** |
| * Constructor. |
| * |
| * @param disabled If <jk>true</jk> then the cache is disabled. |
| * @param maxSize The maximum size of the cache. If this threshold is reached, the cache is flushed. |
| */ |
| public Cache(boolean disabled, int maxSize) { |
| this.nocache = disabled; |
| this.maxSize = maxSize; |
| if (! nocache) |
| cache = new ConcurrentHashMap<>(); |
| else |
| cache = null; |
| } |
| |
| /** |
| * Retrieves the value with the specified key from this cache. |
| * |
| * @param key The key. |
| * @return The value, or <jk>null</jk> if the value is not in the cache, or the cache is disabled. |
| */ |
| public V get(K key) { |
| if (nocache) |
| return null; |
| return cache.get(key); |
| } |
| |
| /** |
| * Adds the value with the specified key to this cache. |
| * |
| * @param key The key. |
| * @param value The value. |
| * @return |
| * Either the value already in the cache if it already exists, or the same value passed in. |
| * Always returns the same value if the cache is disabled. |
| */ |
| public V put(K key, V value) { |
| if (nocache) |
| return value; |
| |
| // Prevent OOM in case of DDOS |
| if (cache.size() > maxSize) |
| cache.clear(); |
| |
| while (true) { |
| V v = cache.get(key); |
| if (v != null) |
| return v; |
| cache.putIfAbsent(key, value); |
| return value; |
| } |
| } |
| } |