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.slf4j;
018
019import org.apache.logging.log4j.LogManager;
020import org.apache.logging.log4j.LoggingException;
021import org.apache.logging.log4j.spi.AbstractLoggerAdapter;
022import org.apache.logging.log4j.spi.LoggerContext;
023import org.apache.logging.log4j.status.StatusLogger;
024import org.apache.logging.log4j.util.StackLocatorUtil;
025import org.slf4j.ILoggerFactory;
026import org.slf4j.Logger;
027
028import java.util.function.Predicate;
029
030/**
031 * Log4j implementation of SLF4J ILoggerFactory interface.
032 */
033public class Log4jLoggerFactory extends AbstractLoggerAdapter<Logger> implements ILoggerFactory {
034
035    private static final StatusLogger LOGGER = StatusLogger.getLogger();
036    private static final String SLF4J_PACKAGE = "org.slf4j";
037    private static final String TO_SLF4J_CONTEXT = "org.apache.logging.slf4j.SLF4JLoggerContext";
038    private static final Predicate<Class<?>> CALLER_PREDICATE = clazz ->
039            !AbstractLoggerAdapter.class.equals(clazz) && !clazz.getName().startsWith(SLF4J_PACKAGE);
040
041    @Override
042    protected Logger newLogger(final String name, final LoggerContext context) {
043        final String key = Logger.ROOT_LOGGER_NAME.equals(name) ? LogManager.ROOT_LOGGER_NAME : name;
044        return new Log4jLogger(validateContext(context).getLogger(key), name);
045    }
046
047    @Override
048    protected LoggerContext getContext() {
049        final Class<?> anchor = LogManager.getFactory().isClassLoaderDependent()
050                ? StackLocatorUtil.getCallerClass(Log4jLoggerFactory.class, CALLER_PREDICATE)
051                : null;
052        LOGGER.trace("Log4jLoggerFactory.getContext() found anchor {}", anchor);
053        return anchor == null
054                ? LogManager.getContext(false)
055                : getContext(anchor);
056    }
057
058    private LoggerContext validateContext(final LoggerContext context) {
059        if (TO_SLF4J_CONTEXT.equals(context.getClass().getName())) {
060            throw new LoggingException("log4j-slf4j-impl cannot be present with log4j-to-slf4j");
061        }
062        return context;
063    }
064}