code not working properly

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub response.setContentType("text/html"); PrintWriter out=response.getWriter(); HttpSession session=request.getSession(); session.setAttribute("lErrorMsg",null); String target="jsp/hrms_default.jsp"; String action=request.getParameter("action_submit"); //String actionchngpswd=request.getParameter("actionchngpswd"); //String username=request.getParameter("username"); System.out.println("user_name");

/* If the details are submitted with the user name and other fields */
    System.out.println(action);
    if(action.equalsIgnoreCase("hrms_user_login_submit"))
    {
        /* Requesting all the details from the jsp page */

        System.out.println("inside action_submit");
        String userId=request.getParameter("user_id");
        String userName=request.getParameter("user_name");
        String password=request.getParameter("user_password");
        System.out.println(userId);

        /* Setting the details to the bean class */

        userLogin_bean obj=new userLogin_bean();
        obj.setUser_Id(userId);
        obj.setPassword(password);
        obj.setUserName(userName);

        userLogin_model modelObj=new userLogin_model();
        System.out.println("model obj created");
        try 
        {
            boolean valid=modelObj.checkLogin(obj);
            if(valid==true)
            {
                System.out.println("user valid");
                 target="jsp/hrms_default.jsp";

            }

            else
            {
                System.out.println("invalid user");
            //  String lErrorMsg="user does not exist";
                //session.setAttribute("lErrorMsg",lErrorMsg);
                target="jsp/Hrms_user_login.jsp";


            }
            //RequestDispatcher requestDispatcher=request.getRequestDispatcher(target);
            //requestDispatcher.forward(request, response);
        }
        catch (SQLException e) 
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    RequestDispatcher requestDispatcher=request.getRequestDispatcher(target);
    requestDispatcher.forward(request, response);

}

}

in the above code if i enter a valid username and password i am redirected to the correct page but if i enter an invalid details at the first attempt i am redirected to the correct page but after that if i again try to login using either the correct or incorrect details i am not directed to the proper page.. please help....