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
022 import org.apache.hadoop.classification.InterfaceAudience;
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 java.io.IOException;
031 import java.net.InetAddress;
032 import java.net.UnknownHostException;
033 import org.slf4j.Logger;
034 import org.slf4j.LoggerFactory;
035
036 /**
037 * Filter that resolves the requester hostname.
038 */
039 @InterfaceAudience.Private
040 public class HostnameFilter implements Filter {
041 static final ThreadLocal<String> HOSTNAME_TL = new ThreadLocal<String>();
042 private static final Logger log = LoggerFactory.getLogger(HostnameFilter.class);
043
044 /**
045 * Initializes the filter.
046 * <p/>
047 * This implementation is a NOP.
048 *
049 * @param config filter configuration.
050 *
051 * @throws ServletException thrown if the filter could not be initialized.
052 */
053 @Override
054 public void init(FilterConfig config) throws ServletException {
055 }
056
057 /**
058 * Resolves the requester hostname and delegates the request to the chain.
059 * <p/>
060 * The requester hostname is available via the {@link #get} method.
061 *
062 * @param request servlet request.
063 * @param response servlet response.
064 * @param chain filter chain.
065 *
066 * @throws IOException thrown if an IO error occurrs.
067 * @throws ServletException thrown if a servet error occurrs.
068 */
069 @Override
070 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
071 throws IOException, ServletException {
072 try {
073 String hostname;
074 try {
075 String address = request.getRemoteAddr();
076 if (address != null) {
077 hostname = InetAddress.getByName(address).getCanonicalHostName();
078 } else {
079 log.warn("Request remote address is NULL");
080 hostname = "???";
081 }
082 } catch (UnknownHostException ex) {
083 log.warn("Request remote address could not be resolved, {0}", ex.toString(), ex);
084 hostname = "???";
085 }
086 HOSTNAME_TL.set(hostname);
087 chain.doFilter(request, response);
088 } finally {
089 HOSTNAME_TL.remove();
090 }
091 }
092
093 /**
094 * Returns the requester hostname.
095 *
096 * @return the requester hostname.
097 */
098 public static String get() {
099 return HOSTNAME_TL.get();
100 }
101
102 /**
103 * Destroys the filter.
104 * <p/>
105 * This implementation is a NOP.
106 */
107 @Override
108 public void destroy() {
109 }
110 }