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 */
017package org.apache.logging.log4j.core.appender;
018
019import java.util.HashMap;
020import java.util.Map;
021import java.util.concurrent.locks.Lock;
022import java.util.concurrent.locks.ReentrantLock;
023
024import org.apache.logging.log4j.Logger;
025import org.apache.logging.log4j.status.StatusLogger;
026
027/**
028 * Abstract base class used to register managers.
029 */
030public 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}