001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019 package org.apache.hadoop.lib.servlet;
020
021 import org.apache.hadoop.classification.InterfaceAudience;
022 import org.slf4j.MDC;
023
024 import javax.servlet.Filter;
025 import javax.servlet.FilterChain;
026 import javax.servlet.FilterConfig;
027 import javax.servlet.ServletException;
028 import javax.servlet.ServletRequest;
029 import javax.servlet.ServletResponse;
030 import javax.servlet.http.HttpServletRequest;
031 import java.io.IOException;
032 import java.security.Principal;
033
034 /**
035 * Filter that sets request contextual information for the slf4j MDC.
036 * <p/>
037 * It sets the following values:
038 * <ul>
039 * <li>hostname: if the {@link HostnameFilter} is present and configured
040 * before this filter</li>
041 * <li>user: the <code>HttpServletRequest.getUserPrincipal().getName()</code></li>
042 * <li>method: the HTTP method fo the request (GET, POST, ...)</li>
043 * <li>path: the path of the request URL</li>
044 * </ul>
045 */
046 @InterfaceAudience.Private
047 public class MDCFilter implements Filter {
048
049 /**
050 * Initializes the filter.
051 * <p/>
052 * This implementation is a NOP.
053 *
054 * @param config filter configuration.
055 *
056 * @throws ServletException thrown if the filter could not be initialized.
057 */
058 @Override
059 public void init(FilterConfig config) throws ServletException {
060 }
061
062 /**
063 * Sets the slf4j <code>MDC</code> and delegates the request to the chain.
064 *
065 * @param request servlet request.
066 * @param response servlet response.
067 * @param chain filter chain.
068 *
069 * @throws IOException thrown if an IO error occurrs.
070 * @throws ServletException thrown if a servet error occurrs.
071 */
072 @Override
073 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
074 throws IOException, ServletException {
075 try {
076 MDC.clear();
077 String hostname = HostnameFilter.get();
078 if (hostname != null) {
079 MDC.put("hostname", HostnameFilter.get());
080 }
081 Principal principal = ((HttpServletRequest) request).getUserPrincipal();
082 String user = (principal != null) ? principal.getName() : null;
083 if (user != null) {
084 MDC.put("user", user);
085 }
086 MDC.put("method", ((HttpServletRequest) request).getMethod());
087 MDC.put("path", ((HttpServletRequest) request).getPathInfo());
088 chain.doFilter(request, response);
089 } finally {
090 MDC.clear();
091 }
092 }
093
094 /**
095 * Destroys the filter.
096 * <p/>
097 * This implementation is a NOP.
098 */
099 @Override
100 public void destroy() {
101 }
102 }
103