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.slf4j.MDC;
022    
023    import javax.servlet.Filter;
024    import javax.servlet.FilterChain;
025    import javax.servlet.FilterConfig;
026    import javax.servlet.ServletException;
027    import javax.servlet.ServletRequest;
028    import javax.servlet.ServletResponse;
029    import javax.servlet.http.HttpServletRequest;
030    import java.io.IOException;
031    import java.security.Principal;
032    
033    /**
034     * Filter that sets request contextual information for the slf4j MDC.
035     * <p/>
036     * It sets the following values:
037     * <ul>
038     * <li>hostname: if the {@link HostnameFilter} is present and configured
039     * before this filter</li>
040     * <li>user: the <code>HttpServletRequest.getUserPrincipal().getName()</code></li>
041     * <li>method: the HTTP method fo the request (GET, POST, ...)</li>
042     * <li>path: the path of the request URL</li>
043     * </ul>
044     */
045    public class MDCFilter implements Filter {
046    
047      /**
048       * Initializes the filter.
049       * <p/>
050       * This implementation is a NOP.
051       *
052       * @param config filter configuration.
053       *
054       * @throws ServletException thrown if the filter could not be initialized.
055       */
056      @Override
057      public void init(FilterConfig config) throws ServletException {
058      }
059    
060      /**
061       * Sets the slf4j <code>MDC</code> and delegates the request to the chain.
062       *
063       * @param request servlet request.
064       * @param response servlet response.
065       * @param chain filter chain.
066       *
067       * @throws IOException thrown if an IO error occurrs.
068       * @throws ServletException thrown if a servet error occurrs.
069       */
070      @Override
071      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
072        throws IOException, ServletException {
073        try {
074          MDC.clear();
075          String hostname = HostnameFilter.get();
076          if (hostname != null) {
077            MDC.put("hostname", HostnameFilter.get());
078          }
079          Principal principal = ((HttpServletRequest) request).getUserPrincipal();
080          String user = (principal != null) ? principal.getName() : null;
081          if (user != null) {
082            MDC.put("user", user);
083          }
084          MDC.put("method", ((HttpServletRequest) request).getMethod());
085          MDC.put("path", ((HttpServletRequest) request).getPathInfo());
086          chain.doFilter(request, response);
087        } finally {
088          MDC.clear();
089        }
090      }
091    
092      /**
093       * Destroys the filter.
094       * <p/>
095       * This implementation is a NOP.
096       */
097      @Override
098      public void destroy() {
099      }
100    }
101