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 org.apache.logging.log4j.Logger;
020    import org.apache.logging.log4j.status.StatusLogger;
021    
022    import java.util.HashMap;
023    import java.util.Map;
024    import java.util.concurrent.locks.Lock;
025    import java.util.concurrent.locks.ReentrantLock;
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                M manager = (M) MAP.get(name);
069                if (manager == null) {
070                    manager = factory.createManager(name, data);
071                    if (manager == null) {
072                        throw new IllegalStateException("Unable to create a manager");
073                    }
074                    MAP.put(name, manager);
075                }
076                manager.count++;
077                return manager;
078            } finally {
079                LOCK.unlock();
080            }
081        }
082    
083        /**
084         * Determines if a Manager with the specified name exists.
085         * @param name The name of the Manager.
086         * @return True if the Manager exists, false otherwise.
087         */
088        public static boolean hasManager(final String name) {
089            LOCK.lock();
090            try {
091                return MAP.containsKey(name);
092            } finally {
093                LOCK.unlock();
094            }
095        }
096    
097        /**
098         * May be overridden by Managers to perform processing while the Manager is being released and the
099         * lock is held.
100         */
101        protected void releaseSub() {
102        }
103    
104        protected int getCount() {
105            return count;
106        }
107    
108        /**
109         * Called to signify that this Manager is no longer required by an Appender.
110         */
111        public void release() {
112            LOCK.lock();
113            try {
114                --count;
115                if (count <= 0) {
116                    MAP.remove(name);
117                    LOGGER.debug("Shutting down {} {}", this.getClass().getSimpleName(), getName());
118                    releaseSub();
119                }
120            } finally {
121                LOCK.unlock();
122            }
123        }
124    
125        /**
126         * Returns the name of the Manager.
127         * @return The name of the Manager.
128         */
129        public String getName() {
130            return name;
131        }
132    
133        /**
134         * Provide a description of the content format supported by this Manager.  Default implementation returns an empty (unspecified) Map.
135         *
136         * @return a Map of key/value pairs describing the Manager-specific content format, or an empty Map if no content format descriptors are specified. 
137         *
138         */
139        public Map<String, String> getContentFormat() {
140            return new HashMap<String, String>();
141        }
142    }