1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.logging.log4j.core.config.plugins.util; 19 20 import java.io.Serializable; 21 import java.util.Map; 22 import java.util.Set; 23 import java.util.concurrent.ConcurrentHashMap; 24 import java.util.concurrent.ConcurrentMap; 25 26 /** 27 * Registry for PluginType maps partitioned by category names. 28 * 29 * @param <T> plugin information object such as PluginType or PluginEntry. 30 */ 31 public class PluginRegistry<T extends Serializable> { 32 private final ConcurrentMap<String, ConcurrentMap<String, T>> categories = 33 new ConcurrentHashMap<String, ConcurrentMap<String, T>>(); 34 35 /** 36 * Gets or creates a plugin category if not already available. Category names are case-insensitive. The 37 * ConcurrentMap that is returned should also be treated as a case-insensitive plugin map where names should be 38 * converted to lowercase before retrieval or storage. 39 * 40 * @param category the plugin category to look up or create. 41 * @return the plugin map for the given category name. 42 * @throws IllegalArgumentException if the argument is {@code null} 43 */ 44 public ConcurrentMap<String, T> getCategory(final String category) { 45 if (category == null) { 46 throw new IllegalArgumentException("Category name cannot be null."); 47 } 48 final String key = category.toLowerCase(); 49 categories.putIfAbsent(key, new ConcurrentHashMap<String, T>()); 50 return categories.get(key); 51 } 52 53 /** 54 * Returns the number of plugin categories currently available. This is primarily useful for serialization. 55 * 56 * @return the number of plugin categories. 57 */ 58 public int getCategoryCount() { 59 return categories.size(); 60 } 61 62 /** 63 * Indicates whether or not any plugin categories have been registered. Note that this does not necessarily 64 * indicate if any plugins are registered as categories may be empty. 65 * 66 * @return {@code true} if there any categories registered. 67 */ 68 public boolean isEmpty() { 69 return categories.isEmpty(); 70 } 71 72 /** 73 * Resets the registry to an empty state. 74 */ 75 public void clear() { 76 categories.clear(); 77 } 78 79 /** 80 * Indicates whether or not the given category name is registered and has plugins in that category. 81 * 82 * @param category the plugin category name to check. 83 * @return {@code true} if the category exists and has plugins registered. 84 * @throws IllegalArgumentException if the argument is {@code null} 85 */ 86 public boolean hasCategory(final String category) { 87 if (category == null) { 88 throw new IllegalArgumentException("Category name cannot be null."); 89 } 90 final String key = category.toLowerCase(); 91 return categories.containsKey(key) && !categories.get(key).isEmpty(); 92 } 93 94 /** 95 * Gets an entry set for iterating over the registered plugin categories. 96 * 97 * @return an entry set of the registered plugin categories. 98 */ 99 public Set<Map.Entry<String, ConcurrentMap<String, T>>> getCategories() { 100 return categories.entrySet(); 101 } 102 }