001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017 package org.apache.logging.log4j.core.appender;
018
019 import java.util.HashMap;
020 import java.util.Map;
021 import java.util.concurrent.locks.Lock;
022 import java.util.concurrent.locks.ReentrantLock;
023
024 import org.apache.logging.log4j.Logger;
025 import org.apache.logging.log4j.status.StatusLogger;
026
027 /**
028 * Abstract base class used to register managers.
029 */
030 public abstract class AbstractManager {
031
032 /**
033 * Allow subclasses access to the status logger without creating another instance.
034 */
035 protected static final Logger LOGGER = StatusLogger.getLogger();
036
037 // Need to lock that map instead of using a ConcurrentMap due to stop removing the
038 // manager from the map and closing the stream, requiring the whole stop method to be locked.
039 private static final Map<String, AbstractManager> MAP = new HashMap<String, AbstractManager>();
040
041 private static final Lock LOCK = new ReentrantLock();
042
043 /**
044 * Number of Appenders using this manager.
045 */
046 protected int count;
047
048 private final String name;
049
050 protected AbstractManager(final String name) {
051 this.name = name;
052 LOGGER.debug("Starting {} {}", this.getClass().getSimpleName(), name);
053 }
054
055 /**
056 * Retrieves a Manager if it has been previously created or creates a new Manager.
057 * @param name The name of the Manager to retrieve.
058 * @param factory The Factory to use to create the Manager.
059 * @param data An Object that should be passed to the factory when creating the Manager.
060 * @param <M> The Type of the Manager to be created.
061 * @param <T> The type of the Factory data.
062 * @return A Manager with the specified name and type.
063 */
064 public static <M extends AbstractManager, T> M getManager(final String name, final ManagerFactory<M, T> factory,
065 final T data) {
066 LOCK.lock();
067 try {
068 @SuppressWarnings("unchecked")
069 M manager = (M) MAP.get(name);
070 if (manager == null) {
071 manager = factory.createManager(name, data);
072 if (manager == null) {
073 throw new IllegalStateException("Unable to create a manager");
074 }
075 MAP.put(name, manager);
076 }
077 manager.count++;
078 return manager;
079 } finally {
080 LOCK.unlock();
081 }
082 }
083
084 /**
085 * Determines if a Manager with the specified name exists.
086 * @param name The name of the Manager.
087 * @return True if the Manager exists, false otherwise.
088 */
089 public static boolean hasManager(final String name) {
090 LOCK.lock();
091 try {
092 return MAP.containsKey(name);
093 } finally {
094 LOCK.unlock();
095 }
096 }
097
098 /**
099 * May be overridden by Managers to perform processing while the Manager is being released and the
100 * lock is held.
101 */
102 protected void releaseSub() {
103 }
104
105 protected int getCount() {
106 return count;
107 }
108
109 /**
110 * Called to signify that this Manager is no longer required by an Appender.
111 */
112 public void release() {
113 LOCK.lock();
114 try {
115 --count;
116 if (count <= 0) {
117 MAP.remove(name);
118 LOGGER.debug("Shutting down {} {}", this.getClass().getSimpleName(), getName());
119 releaseSub();
120 }
121 } finally {
122 LOCK.unlock();
123 }
124 }
125
126 /**
127 * Returns the name of the Manager.
128 * @return The name of the Manager.
129 */
130 public String getName() {
131 return name;
132 }
133
134 /**
135 * Provide a description of the content format supported by this Manager. Default implementation returns an empty
136 * (unspecified) Map.
137 *
138 * @return a Map of key/value pairs describing the Manager-specific content format, or an empty Map if no content
139 * format descriptors are specified.
140 */
141 public Map<String, String> getContentFormat() {
142 return new HashMap<String, String>();
143 }
144 }