Cannot access filter Servlet's session attribute from another normal Http Servlet
public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {
    HttpServletRequest httpReq = (HttpServletRequest) request;
    HttpServletResponse httpResp = (HttpServletResponse) response;
    HttpSession session = httpReq.getSession();

    httpReq.setCharacterEncoding("UTF-8");

    UserDTO dto = new UserDTO();
    session.setAttribute("system.userinfo", dto);

    chain.doFilter(request, response);

}


public class FileUpload extends HttpServlet {
    @SuppressWarnings("unchecked")
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        response.setCharacterEncoding("UTF-8");

        // cannot get anything here
        UserDTO userinfo = (UserDTO)request.getSession(false).getAttribute("system.userinfo");


        }
}