/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.classic.helpers;
  
  import java.io.IOException;
  
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  
  import org.slf4j.MDC;
  
  import ch.qos.logback.classic.ClassicConstants;
  
  /**
   * A servlet filter that inserts various values retrieved from the incoming http
   * request into the MDC.
   * <p/>
   * <p/>
   * The values are removed after the request is processed.
   *
   * @author Ceki G&uuml;lc&uuml;
   */
  public class MDCInsertingServletFilter implements Filter {
  
    public void destroy() {
      // do nothing
    }
  
    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain) throws IOException, ServletException {
  
  
      insertIntoMDC(request);
      try {
        chain.doFilter(request, response);
      } finally {
        clearMDC();
      }
    }
  
    void insertIntoMDC(ServletRequest request) {
  
      MDC.put(ClassicConstants.REQUEST_REMOTE_HOST_MDC_KEY, request
              .getRemoteHost());
  
      if (request instanceof HttpServletRequest) {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        MDC.put(ClassicConstants.REQUEST_REQUEST_URI, httpServletRequest
                .getRequestURI());
        StringBuffer requestURL = httpServletRequest.getRequestURL();
        if (requestURL != null) {
          MDC.put(ClassicConstants.REQUEST_REQUEST_URL, requestURL.toString());
        }
        MDC.put(ClassicConstants.REQUEST_QUERY_STRING, httpServletRequest.getQueryString());
        MDC.put(ClassicConstants.REQUEST_USER_AGENT_MDC_KEY, httpServletRequest
                .getHeader("User-Agent"));
        MDC.put(ClassicConstants.REQUEST_X_FORWARDED_FOR, httpServletRequest
                .getHeader("X-Forwarded-For"));
      }
  
    }
  
    void clearMDC() {
      MDC.remove(ClassicConstants.REQUEST_REMOTE_HOST_MDC_KEY);
      MDC.remove(ClassicConstants.REQUEST_REQUEST_URI);
      MDC.remove(ClassicConstants.REQUEST_QUERY_STRING);
      // removing possibly inexistent item is OK
      MDC.remove(ClassicConstants.REQUEST_REQUEST_URL);
      MDC.remove(ClassicConstants.REQUEST_USER_AGENT_MDC_KEY);
      MDC.remove(ClassicConstants.REQUEST_X_FORWARDED_FOR);
    }
  
    public void init(FilterConfig arg0) throws ServletException {
      // do nothing
    }
  }