public class LoginServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;
    private static final UserServiceInterface userService=UserService
            .getInstance();
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("user");
        String password = request.getParameter("password");
        User user = new User(username,password);
        try {
            if (userService.isValid(user)) {
                HttpSession session = request.getSession();
                session.setAttribute("user", username);
                session.setMaxInactiveInterval(30 * 60);
                Cookie userName = new Cookie("user", username);
                userName.setMaxAge(30 * 60);
                response.sendRedirect("customers.jsp");
            } else {
            }
        } catch (DaoException ex) {
            response.sendRedirect("error.jsp");
        }

    }
}