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.slf4j.helpers;
018    
019    import java.util.Map;
020    import java.util.WeakHashMap;
021    import java.util.concurrent.ConcurrentHashMap;
022    import java.util.concurrent.ConcurrentMap;
023    
024    import org.apache.logging.log4j.LogManager;
025    import org.apache.logging.log4j.spi.AbstractLogger;
026    import org.apache.logging.log4j.spi.LoggerContext;
027    import org.apache.logging.slf4j.SLF4JLoggingException;
028    import org.slf4j.ILoggerFactory;
029    import org.slf4j.Logger;
030    import org.slf4j.LoggerFactory;
031    import org.slf4j.impl.SLF4JLogger;
032    
033    /**
034     *
035     */
036    public class Log4jLoggerFactory implements ILoggerFactory {
037    
038        private static final String FQCN = Log4jLoggerFactory.class.getName();
039        private static final String PACKAGE = "org.slf4j";
040    
041        private final Map<LoggerContext, ConcurrentMap<String, Logger>> contextMap =
042            new WeakHashMap<LoggerContext, ConcurrentMap<String, Logger>>();
043    
044        @Override
045        public Logger getLogger(final String name) {
046            final LoggerContext context = getContext();
047            final ConcurrentMap<String, Logger> loggers = getLoggersMap(context);
048    
049            if (loggers.containsKey(name)) {
050                return loggers.get(name);
051            }
052            final String key = Logger.ROOT_LOGGER_NAME.equals(name) ? LogManager.ROOT_LOGGER_NAME : name;
053            final org.apache.logging.log4j.Logger logger = context.getLogger(key);
054            if (logger instanceof AbstractLogger) {
055                loggers.putIfAbsent(name, new SLF4JLogger((AbstractLogger) logger, name));
056                return loggers.get(name);
057            }
058            throw new SLF4JLoggingException("SLF4J Adapter requires base logging system to extend Log4j AbstractLogger");
059        }
060    
061        private ConcurrentMap<String, Logger> getLoggersMap(final LoggerContext context) {
062            synchronized (contextMap) {
063                ConcurrentMap<String, Logger> map = contextMap.get(context);
064                if (map == null) {
065                    map = new ConcurrentHashMap<String, Logger>();
066                    contextMap.put(context, map);
067                }
068                return map;
069            }
070        }
071        private LoggerContext getContext() {
072            final Throwable t = new Throwable();
073            boolean next = false;
074            boolean pkg = false;
075            String fqcn = LoggerFactory.class.getName();
076            for (final StackTraceElement element : t.getStackTrace()) {
077                if (FQCN.equals(element.getClassName())) {
078                    next = true;
079                    continue;
080                }
081                if (next && element.getClassName().startsWith(PACKAGE)) {
082                    fqcn = element.getClassName();
083                    pkg = true;
084                    continue;
085                }
086                if (pkg) {
087                    break;
088                }
089            }
090            return PrivateManager.getContext(fqcn);
091        }
092    
093        /**
094         * The real bridge between SLF4J and Log4j.
095         */
096        private static class PrivateManager extends LogManager {
097            private static final String FQCN = LoggerFactory.class.getName();
098    
099            public static LoggerContext getContext() {
100                return getContext(FQCN, false);
101            }
102    
103            public static LoggerContext getContext(final String fqcn) {
104                return getContext(fqcn, false);
105            }
106    
107            public static org.apache.logging.log4j.Logger getLogger(final String name) {
108                return getLogger(FQCN, name);
109            }
110        }
111    
112    }