Ajax传输数据request.getParameter("key")获取为空

 var data = {
                sno:sno,
                password:password,
                verifyCode:verifyCode,
                status:status
            }
            $.ajax({
                type: 'Post',
                url: "/DormController/checkLogin",
                contentType:"application/json",
                data: JSON.stringify(data),
                dataType: "text", //返回数据类型
                success: function (msg) {
                    if ("success" == msg) {
                        window.location.href = "/DormController/index";
                    } else {
                        $.messager.alert("消息提醒", msg, "warning");
                        $("#vcodeImg").click();//切换验证码
                        $("input[name='vcode']").val("");//清空验证码输入框
                    }
                }
            });

@ResponseBody
@RequestMapping("/checkLogin")
public String checkLogin(@RequestBody Map<String, String> map, HttpSession session) {
　　if (!map.get("verifyCode").equals(session.getAttribute("verify"))) {
            return "验证码不正确";
    }
    List<User> users = userService.findUserByStatus(Integer.parseInt(map.get("status")));
    System.out.println("sno---->"+map.get("sno"));
    if (Integer.parseInt(map.get("status")) == 1) {
        //超级管理员用户
        for (User user1 : users) {
            if (user1.getSno().equals(map.get("sno")) && user1.getPassword().equals(map.get("password"))) {
                session.setAttribute("user", user1);
                return "success";
            }
        }
        return "用户名或密码不正确！";
    }
}