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.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; 027 028/** 029 * This is responsible for the following: 030 * <ul> 031 * <li>Clearing the logger context when the application has finished starting up.</li> 032 * <li>Setting the logger context before processing a request and clearing it after processing a request.</li> 033 * <li>Setting the logger context when the application is starting to shut down.</li> 034 * </ul> 035 * This filter is a once-per-request filter. It is capable of filtering all the different types of requests 036 * (standard, asynchronous, error, etc.) but will not apply processing if the filter matches multiple times on the same 037 * logical request. 038 */ 039public class Log4jServletFilter implements Filter { 040 041 static final String ALREADY_FILTERED_ATTRIBUTE = Log4jServletFilter.class.getName() + ".FILTERED"; 042 043 private ServletContext servletContext; 044 private Log4jWebInitializer initializer; 045 046 @Override 047 public void init(final FilterConfig filterConfig) throws ServletException { 048 this.servletContext = filterConfig.getServletContext(); 049 this.servletContext.log("Log4jServletFilter initialized."); 050 051 this.initializer = Log4jWebInitializerImpl.getLog4jWebInitializer(this.servletContext); 052 this.initializer.clearLoggerContext(); // the application is mostly finished starting up now 053 } 054 055 @Override 056 public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain) 057 throws IOException, ServletException { 058 if (request.getAttribute(ALREADY_FILTERED_ATTRIBUTE) != null) { 059 chain.doFilter(request, response); 060 } else { 061 request.setAttribute(ALREADY_FILTERED_ATTRIBUTE, true); 062 063 try { 064 this.initializer.setLoggerContext(); 065 066 chain.doFilter(request, response); 067 } finally { 068 this.initializer.clearLoggerContext(); 069 } 070 } 071 } 072 073 @Override 074 public void destroy() { 075 if (this.servletContext == null || this.initializer == null) { 076 throw new IllegalStateException("Filter destroyed before it was initialized."); 077 } 078 this.servletContext.log("Log4jServletFilter destroyed."); 079 080 this.initializer.setLoggerContext(); // the application is just now starting to shut down 081 } 082}