Servlet Jsp Login Problen

Question

Consider 4 pages
default.jsp          -          Default page     -     Provides link to update.jsp
Update.jsp          -          Update Page          -     User came through default page
login.jsp          -          Displays html      -     Two Input tags user & pass
check Servlet     -          Authentication     -     Validates userid & pwd from database
what I want to do ?
1     User clicks on update link on default page
2     update checks for session as
          String user = (String) session.getAttribute("user");
          if( user == null )                    
               response.sendRedirect("/login.jsp");
3     Now login.jsp displays the HTML form with action = /servlet/check          
4     check servlet revceives values user & pass from HTML response & validates through
     database
5     Now if validation succedes it must redirect to the actual page that user had
     requested for ultimately i.e update.jsp
6 HOW MANY WAYS I CAN DO THIS
7      Problem becomes more serious when along with login & check other intermediate
     servlets are also there.
8     The final problem is
     1     Update.jsp receives request data from some HTML form but checks for user
          from session object.
     2     If found null redirect to login page
     3     The above prob. now repeats but the point is after authentication
          the check servlet not only redirects to the actual requested page but
          also supplies the data that update.jsp has received
Please reply soon

Answer 1

Thanx Sir!
But i want to have a more generic solution
like using <jsp:fordward> & <jsp:param> etc
but i want it so generic that it can be done in ASP/ JSP
preferably without using queryString
And the main point is this problen
request.setAttribute() is not working
I am uploading the code
CODE:
default.jsp     Update
update.jsp     String user = (String) session.getAttribute("user");
          if( user == null )     {
               String look_for = request.getRequestURI();
               request.setAttribute("look_for",look_for);
               response.sendRedirect("/login.jsp");
login.jsp     String req = null;
          req = (String)request.getAttribute("req");
          //out.print(req); --> Error Printing null
          request.setAttribute("req", req);
          <form----
          >
          response.sendRidirect("/servlet/check");
check     
     String user = null;
String look_for = (String)request.getAttribute("req");
if(look_for == null)     {
          request.setAttribute("req", look_for);
     response.sendRedirect(request.getHeader("HTTP_REFERER"));
if(user != "Hemant") {
request.setAttribute("req",look_for);
response.sendRedirect("/login.jsp");
HttpSession session = request.getSession();
session.setAttribute("user","Hemant");
response.sendRedirect(look_for);
out.close();