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 javax.servlet.Filter; 023 import javax.servlet.FilterChain; 024 import javax.servlet.FilterConfig; 025 import javax.servlet.ServletException; 026 import javax.servlet.ServletRequest; 027 import javax.servlet.ServletResponse; 028 import java.io.IOException; 029 import java.net.InetAddress; 030 031 /** 032 * Filter that resolves the requester hostname. 033 */ 034 public class HostnameFilter implements Filter { 035 static final ThreadLocal<String> HOSTNAME_TL = new ThreadLocal<String>(); 036 037 /** 038 * Initializes the filter. 039 * <p/> 040 * This implementation is a NOP. 041 * 042 * @param config filter configuration. 043 * 044 * @throws ServletException thrown if the filter could not be initialized. 045 */ 046 @Override 047 public void init(FilterConfig config) throws ServletException { 048 } 049 050 /** 051 * Resolves the requester hostname and delegates the request to the chain. 052 * <p/> 053 * The requester hostname is available via the {@link #get} method. 054 * 055 * @param request servlet request. 056 * @param response servlet response. 057 * @param chain filter chain. 058 * 059 * @throws IOException thrown if an IO error occurrs. 060 * @throws ServletException thrown if a servet error occurrs. 061 */ 062 @Override 063 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 064 throws IOException, ServletException { 065 try { 066 String hostname = InetAddress.getByName(request.getRemoteAddr()).getCanonicalHostName(); 067 HOSTNAME_TL.set(hostname); 068 chain.doFilter(request, response); 069 } finally { 070 HOSTNAME_TL.remove(); 071 } 072 } 073 074 /** 075 * Returns the requester hostname. 076 * 077 * @return the requester hostname. 078 */ 079 public static String get() { 080 return HOSTNAME_TL.get(); 081 } 082 083 /** 084 * Destroys the filter. 085 * <p/> 086 * This implementation is a NOP. 087 */ 088 @Override 089 public void destroy() { 090 } 091 }