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    }