request.getParameter后台取不到值

下边的是form代码

        下边是后台servelet代码
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    response.setCharacterEncoding("UTF-8");
    String action = request.getParameter("action");
    //这的action就能取到值
    if(action.equals("login")){
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //这的username和password就取不到值，为什么啊？
        User u = userservice.login(username, password);
        if(u!=null){
            if(u.getIsDelete()==0){
                request.getSession().setAttribute("user", u);
                response.sendRedirect("user?action=index");
            }else{
                request.getSession().setAttribute("userIsDeleMsg", "该用户已被禁用，无法登录！");
                request.getRequestDispatcher("login.jsp").forward(request, response);
            }
        }else {
            request.getSession().setAttribute("msg", "验证失败，请重新输入用户名或密码！");
            response.sendRedirect("Login.jsp");
        }
    }else if(action.equals("index")){
        //跳转到首页           
        request.getRequestDispatcher("/index.jsp").forward(request, response);
    }
}

form代码怎么显示不出来？

                <div class="form-group">
                    <label for="username">用户名</label> 
                    <input type="text"
                        class="form-control " name="username" id="username"
                        placeholder="Enter email">
                </div>
                <div class="form-group">
                    <label for="password">密码</label> <input type="password"
                        class="form-control" name="password" id="password"
                        placeholder="Password">
                </div>

                <div class="form-group">
                <button type="submit" class="btn btn-success">登录</button>
                </div>
            </fieldset>
        </form>
    </div>
</div>