Servlet session maintenance - to disable caching

                   // Set to expire far in the past.
  response.setHeader("Expires", "Sat, 6 May 1995 12:00:00 GMT");

  // Set standard HTTP/1.1 no-cache headers.
  response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");

  // Set IE extended HTTP/1.1 no-cache headers (use addHeader).
  response.addHeader("Cache-Control", "post-check=0, pre-check=0");

  // Set standard HTTP/1.0 no-cache header.
  response.setHeader("Pragma", "no-cache");