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.web;
018
019import java.io.IOException;
020import javax.servlet.Filter;
021import javax.servlet.FilterChain;
022import javax.servlet.FilterConfig;
023import javax.servlet.ServletContext;
024import javax.servlet.ServletException;
025import javax.servlet.ServletRequest;
026import javax.servlet.ServletResponse;
027
028import org.apache.logging.log4j.Logger;
029import org.apache.logging.log4j.status.StatusLogger;
030
031/**
032 * This is responsible for the following:
033 * <ul>
034 *     <li>Clearing the logger context when the application has finished starting up.</li>
035 *     <li>Setting the logger context before processing a request and clearing it after processing a request.</li>
036 *     <li>Setting the logger context when the application is starting to shut down.</li>
037 * </ul>
038 * This filter is a once-per-request filter. It is capable of filtering all the different types of requests
039 * (standard, asynchronous, error, etc.) but will not apply processing if the filter matches multiple times on the same
040 * logical request.
041 */
042public class Log4jServletFilter implements Filter {
043
044    private static final Logger LOGGER = StatusLogger.getLogger();
045
046    static final String ALREADY_FILTERED_ATTRIBUTE = Log4jServletFilter.class.getName() + ".FILTERED";
047
048    private ServletContext servletContext;
049    private Log4jWebLifeCycle initializer;
050
051    @Override
052    public void init(final FilterConfig filterConfig) throws ServletException {
053        this.servletContext = filterConfig.getServletContext();
054        LOGGER.debug("Log4jServletFilter initialized.");
055
056        this.initializer = WebLoggerContextUtils.getWebLifeCycle(this.servletContext);
057        this.initializer.clearLoggerContext(); // the application is mostly finished starting up now
058    }
059
060    @Override
061    public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
062            throws IOException, ServletException {
063        if (request.getAttribute(ALREADY_FILTERED_ATTRIBUTE) != null) {
064            chain.doFilter(request, response);
065        } else {
066            request.setAttribute(ALREADY_FILTERED_ATTRIBUTE, Boolean.TRUE);
067
068            try {
069                this.initializer.setLoggerContext();
070
071                chain.doFilter(request, response);
072            } finally {
073                this.initializer.clearLoggerContext();
074            }
075        }
076    }
077
078    @Override
079    public void destroy() {
080        if (this.servletContext == null || this.initializer == null) {
081            throw new IllegalStateException("Filter destroyed before it was initialized.");
082        }
083        LOGGER.debug("Log4jServletFilter destroyed.");
084
085        this.initializer.setLoggerContext(); // the application is just now starting to shut down
086    }
087}