这是返回报错信息：

"status":400

,"error":"Bad Request"

,"message":"Required String parameter

'userName' is not present"

,"path":"/login"

我的代码：

User_info login=new User_info("17375121795","a4721874");
gson=new Gson();
String user_info=gson.toJson(login);
MediaType login_type=MediaType.parse("application/json; charset=utf-8");
body=RequestBody.create(user_info,login_type);
request=new Request.Builder()
        .url(BASE_URL+"/login")
        .post(body)
        .build();
task=client.newCall(request);
task.enqueue(new Callback() {
    @Override
    public void onFailure(@NotNull Call call, @NotNull IOException e) {
        Log.d("result",e.toString());
    }

    @Override
    public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
        Log.d("Success",response.body().string());
    }
});