1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.web;
18
19 import java.io.IOException;
20
21 import javax.servlet.Filter;
22 import javax.servlet.FilterChain;
23 import javax.servlet.FilterConfig;
24 import javax.servlet.ServletContext;
25 import javax.servlet.ServletException;
26 import javax.servlet.ServletRequest;
27 import javax.servlet.ServletResponse;
28
29 /**
30 * This is responsible for the following:
31 * <ul>
32 * <li>Clearing the logger context when the application has finished starting up.</li>
33 * <li>Setting the logger context before processing a request and clearing it after processing a request.</li>
34 * <li>Setting the logger context when the application is starting to shut down.</li>
35 * </ul>
36 * This filter is a once-per-request filter. It is capable of filtering all the different types of requests
37 * (standard, asynchronous, error, etc.) but will not apply processing if the filter matches multiple times on the same
38 * logical request.
39 */
40 public class Log4jServletFilter implements Filter {
41
42 static final String ALREADY_FILTERED_ATTRIBUTE = Log4jServletFilter.class.getName() + ".FILTERED";
43
44 private ServletContext servletContext;
45 private Log4jWebLifeCycle initializer;
46
47 @Override
48 public void init(final FilterConfig filterConfig) throws ServletException {
49 this.servletContext = filterConfig.getServletContext();
50 this.servletContext.log("Log4jServletFilter initialized.");
51
52 this.initializer = Log4jWebInitializerImpl.getLog4jWebInitializer(this.servletContext);
53 this.initializer.clearLoggerContext(); // the application is mostly finished starting up now
54 }
55
56 @Override
57 public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
58 throws IOException, ServletException {
59 if (request.getAttribute(ALREADY_FILTERED_ATTRIBUTE) != null) {
60 chain.doFilter(request, response);
61 } else {
62 request.setAttribute(ALREADY_FILTERED_ATTRIBUTE, true);
63
64 try {
65 this.initializer.setLoggerContext();
66
67 chain.doFilter(request, response);
68 } finally {
69 this.initializer.clearLoggerContext();
70 }
71 }
72 }
73
74 @Override
75 public void destroy() {
76 if (this.servletContext == null || this.initializer == null) {
77 throw new IllegalStateException("Filter destroyed before it was initialized.");
78 }
79 this.servletContext.log("Log4jServletFilter destroyed.");
80
81 this.initializer.setLoggerContext(); // the application is just now starting to shut down
82 }
83 }