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
019package org.apache.oozie.servlet;
020
021import org.apache.oozie.util.XLog;
022
023import javax.servlet.Filter;
024import javax.servlet.FilterChain;
025import javax.servlet.FilterConfig;
026import javax.servlet.ServletException;
027import javax.servlet.ServletRequest;
028import javax.servlet.ServletResponse;
029import java.io.IOException;
030import java.net.InetAddress;
031import java.net.UnknownHostException;
032
033/**
034 * Filter that resolves the requester hostname.
035 */
036public class HostnameFilter implements Filter {
037    private static final XLog LOG = XLog.getLog(HostnameFilter.class);
038
039    static final ThreadLocal<String> HOSTNAME_TL = new ThreadLocal<String>();
040
041    /**
042     * Initializes the filter.
043     * <p/>
044     * This implementation is a NOP.
045     *
046     * @param config filter configuration.
047     *
048     * @throws ServletException thrown if the filter could not be initialized.
049     */
050    @Override
051    public void init(FilterConfig config) throws ServletException {
052    }
053
054    /**
055     * Resolves the requester hostname and delegates the request to the chain.
056     * <p/>
057     * The requester hostname is available via the {@link #get} method.
058     *
059     * @param request servlet request.
060     * @param response servlet response.
061     * @param chain filter chain.
062     *
063     * @throws IOException thrown if an IO error occurrs.
064     * @throws ServletException thrown if a servet error occurrs.
065     */
066    @Override
067    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
068        throws IOException, ServletException {
069        try {
070            String hostname;
071            try {
072                String address = request.getRemoteAddr();
073                if (address != null) {
074                    hostname = InetAddress.getByName(address).getCanonicalHostName();
075                } else {
076                    LOG.warn("Request remote address is NULL");
077                    hostname = "???";
078                }
079            } catch (UnknownHostException ex) {
080                LOG.warn("Request remote address could not be resolved, {0}", ex.toString(), ex);
081                hostname = "???";
082            }
083            HOSTNAME_TL.set(hostname);
084            chain.doFilter(request, response);
085        }
086        finally {
087            HOSTNAME_TL.remove();
088        }
089    }
090
091    /**
092     * Returns the requester hostname.
093     *
094     * @return the requester hostname.
095     */
096    public static String get() {
097        return HOSTNAME_TL.get();
098    }
099
100    /**
101     * Destroys the filter.
102     * <p/>
103     * This implementation is a NOP.
104     */
105    @Override
106    public void destroy() {
107    }
108}