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.spi;
018
019import java.util.HashSet;
020import java.util.Map;
021import java.util.Set;
022import java.util.WeakHashMap;
023import java.util.concurrent.ConcurrentHashMap;
024import java.util.concurrent.ConcurrentMap;
025import java.util.concurrent.locks.ReadWriteLock;
026import java.util.concurrent.locks.ReentrantReadWriteLock;
027
028import org.apache.logging.log4j.LogManager;
029import org.apache.logging.log4j.util.LoaderUtil;
030
031/**
032 * Provides an abstract base class to use for implementing LoggerAdapter.
033 * 
034 * @param <L> the Logger class to adapt
035 * @since 2.1
036 */
037public abstract class AbstractLoggerAdapter<L> implements LoggerAdapter<L>, LoggerContextShutdownAware {
038
039    /**
040     * A map to store loggers for their given LoggerContexts.
041     */
042    protected final Map<LoggerContext, ConcurrentMap<String, L>> registry = new ConcurrentHashMap<>();
043
044    private final ReadWriteLock lock = new ReentrantReadWriteLock (true);
045
046    @Override
047    public L getLogger(final String name) {
048        final LoggerContext context = getContext();
049        final ConcurrentMap<String, L> loggers = getLoggersInContext(context);
050        final L logger = loggers.get(name);
051        if (logger != null) {
052            return logger;
053        }
054        loggers.putIfAbsent(name, newLogger(name, context));
055        return loggers.get(name);
056    }
057
058    @Override
059    public void contextShutdown(LoggerContext loggerContext) {
060        registry.remove(loggerContext);
061    }
062
063    /**
064     * Gets or creates the ConcurrentMap of named loggers for a given LoggerContext.
065     *
066     * @param context the LoggerContext to get loggers for
067     * @return the map of loggers for the given LoggerContext
068     */
069    public ConcurrentMap<String, L> getLoggersInContext(final LoggerContext context) {
070        ConcurrentMap<String, L> loggers;
071        lock.readLock ().lock ();
072        try {
073            loggers = registry.get (context);
074        } finally {
075            lock.readLock ().unlock ();
076        }
077
078        if (loggers != null) {
079            return loggers;
080        }
081        lock.writeLock ().lock ();
082        try {
083            loggers = registry.get (context);
084            if (loggers == null) {
085                loggers = new ConcurrentHashMap<> ();
086                registry.put (context, loggers);
087                if (context instanceof LoggerContextShutdownEnabled) {
088                    ((LoggerContextShutdownEnabled) context).addShutdownListener(this);
089                }
090            }
091            return loggers;
092        } finally {
093            lock.writeLock ().unlock ();
094        }
095    }
096
097    /**
098     * For unit testing. Consider to be private.
099     */
100    public Set<LoggerContext> getLoggerContexts() {
101        return new HashSet<>(registry.keySet());
102    }
103
104    /**
105     * Creates a new named logger for a given {@link LoggerContext}.
106     *
107     * @param name the name of the logger to create
108     * @param context the LoggerContext this logger will be associated with
109     * @return the new named logger
110     */
111    protected abstract L newLogger(final String name, final LoggerContext context);
112
113    /**
114     * Gets the {@link LoggerContext} that should be used to look up or create loggers. This is similar in spirit to the
115     * {@code ContextSelector} class in {@code log4j-core}. However, implementations can rely on their own framework's
116     * separation of contexts instead (or simply use a singleton).
117     *
118     * @return the LoggerContext to be used for lookup and creation purposes
119     * @see org.apache.logging.log4j.LogManager#getContext(ClassLoader, boolean)
120     * @see org.apache.logging.log4j.LogManager#getContext(String, boolean)
121     */
122    protected abstract LoggerContext getContext();
123
124    /**
125     * Gets the {@link LoggerContext} associated with the given caller class.
126     *
127     * @param callerClass the caller class
128     * @return the LoggerContext for the calling class
129     */
130    protected LoggerContext getContext(final Class<?> callerClass) {
131        ClassLoader cl = null;
132        if (callerClass != null) {
133            cl = callerClass.getClassLoader();
134        }
135        if (cl == null) {
136            cl = LoaderUtil.getThreadContextClassLoader();
137        }
138        return LogManager.getContext(cl, false);
139    }
140
141    @Override
142    public void close() {
143        lock.writeLock ().lock ();
144        try {
145            registry.clear();
146        } finally {
147            lock.writeLock ().unlock ();
148        }
149    }
150}