Unity中嵌套类无法反序列化AWS Cognito Auth JSON请求

问题背景 #

在Unity中使用嵌套类反序列化AWS Cognito登录响应JSON时失败，尝试多种方法未解决，以下是相关响应内容、请求代码及解析类结构。

AWS Cognito登录响应JSON #

{
    "timestamp": "2024-05-17T02:14:10.331Z",
    "level": "INFO",
    "requestId": "2dc7b590-1827-4554-9821-908eb1d3ee3f",
    "message": {
        "$metadata": {
            "httpStatusCode": 200,
            "requestId": "0c684225-7a1b-469f-89e3-15d29da36f49",
            "attempts": 1,
            "totalRetryDelay": 0
        },
        "ChallengeName": "NEW_PASSWORD_REQUIRED",
        "ChallengeParameters": {
            "USER_ID_FOR_SRP": "348844c8-e001-7030-93c4-3c5a5a754fa2",
            "requiredAttributes": "[]",
            "userAttributes": "{\"email_verified\":\"true\",\"preferred_username\":\"RobloxHero\",\"email\":\"robloxhero@compassoftruth.org\"}"
        },
        "Session": "AYABeHuZceyPXQVTVA1OPXwrdZIAHQABAAdTZXJ2aWNlABBDb2duaXRvVXNlclBvb2xzAAEAB2F3cy1rbXMAS2Fybjphd3M6a21zOnVzLWVhc3QtMTo3NDU2MjM0Njc1NTU6a2V5L2IxNTVhZmNhLWJmMjktNGVlZC1hZmQ4LWE5ZTA5MzY1M2RiZQC4AQIBAHjHL4WD3WpekpFe85nxP9Nwg99u3bPN6BTSaB-uHZcTLAF1FxlVsAaSp8ntnWxXieO7AAAAfjB8BgkqhkiG9w0BBwagbzBtAgEAMGgGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMjuV5Bhw0j4lWg6JxAgEQgDusJsldE8RrnX72vgmOQkw9KkrzbARBsxGkfjRqS5A6T7T71F6umtOTz7XnjEqdeAfhfyQ2vT_Hmx2-nAIAAAAADAAAEAAAAAAAAAAAAAAAAABejP7rYrS09IQqwZHglO_k_____wAAAAEAAAAAAAAAAAAAAAEAAADVlPZSlzCXntBx_E8TEbzxbn4ZTZBEr5nMSXRinXYnmVRrlKjtLX7yv8giRh1z1_rYNSKGAY2b3cz1PyWadtwifpldG6_d3NdgthTaMpQNeIhJ_jmjfz0U_4hrYWVyz5OspPbR38Rlelj5r9DIQaGWGFMVVDuzeeouxbBTl83O3w5Rx2gYYZ3AmyIBrMiVxDscytZj8oJ4fit76lVlFlFNmwMywy6MjhDb80RGcYoUpkbUZn86X1Ycy5KZstb7tm4dFp7IN1ej69IcLmYZbvcJ4xBCZeEJCrfccFbdhVG0zGcPUB1lzw"
    }
}

Unity登录请求代码 #

public void LoginRequest()
{
    AWSUserLoginRequest request = new AWSUserLoginRequest();
    request.username = username;
    request.password = password;

    using (UnityWebRequest www = UnityWebRequest.Post("https://game-api.compassoftruth.org/prod/Login", JsonUtility.ToJson(request), "application/json") )
    {
        www.SendWebRequest();
        while (www.isDone == false) {
        //do something, or nothing while blocking
        }
        if (www.result != UnityWebRequest.Result.Success) {
            Debug.Log(www.error);
        }
        else {
            LoginResult = JsonUtility.FromJson<AWSLoginResult>(www.downloadHandler.text.Replace('$'.ToString(), ""));
            // Show results as text
            Debug.Log(www.downloadHandler.text.Replace('$'.ToString(), ""));
            Debug.Log(LoginResult.level);
        }
    }
    
}

调试得到的响应字符串 #

{"metadata":{"httpStatusCode":200,"requestId":"731de9a0-a3b3-4a75-a565-f19c49f19a50","attempts":1,"totalRetryDelay":0},"ChallengeName":"NEW_PASSWORD_REQUIRED","ChallengeParameters":{"USER_ID_FOR_SRP":"348844c8-e001-7030-93c4-3c5a5a754fa2","requiredAttributes":"[]","userAttributes":"{\"email_verified\":\"true\",\"preferred_username\":\"RobloxHero\",\"email\":\"robloxhero@compassoftruth.org\"}"},"Session":"AYABeJlFAr90U2rURQa1RoyPy-AAHQABAAdTZXJ2aWNlABBDb2duaXRvVXNlclBvb2xzAAEAB2F3cy1rbXMAS2Fybjphd3M6a21zOnVzLWVhc3QtMTo3NDU2MjM0Njc1NTU6a2V5L2IxNTVhZmNhLWJmMjktNGVlZC1hZmQ4LWE5ZTA5MzY1M2RiZQC4AQIBAHjHL4WD3WpekpFe85nxP9Nwg99u3bPN6BTSaB-uHZcTLAH4F1Ox2jph9NZcOwFtL6m-AAAAfjB8BgkqhkiG9w0BBwagbzBtAgEAMGgGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQM7FLUPDofg4S5f67nAgEQgDsIOeZuVErT75jsNRBJz63Pat7GgObkPeKx7Li_z5tvnDG4FvrbLoLjVcgJpVin-rz9Cp_bcfmxyjX0owIAAAAADAAAEAAAAAAAAAAAAAAAAAAtqnLZ5SIekFGUo3n6YKYi_____wAAAAEAAAAAAAAAAAAAAAEAAADV0iUMK4jkW4ioIy8AGcb5bLTQ3jW90JXuaucWAlImLuT55a3TaWyStOL_O6uJb-2NDqz7ejkQ3eUDlMn02AYwvj75cI4bB6nuaOSomjBZ4-tkT8AtpbykIYTgc451wjg5U9CrnbbTViMR-s3Fdx6P_rABop_INWkf1lAUs1xrlY5AMX3VGc2bjlHX9Ejips9irlVpnuUXic-AJXQUcZeHbi9DmcfSFe0VDTQGWMJmLFUZFWfJAQeo-dvQadfvkm2r1Lwwn42WGVkPykxbVqdkTUxIUcpFajlRAZp5B4PRxoJCBp-CVA"}

用于解析的嵌套类结构 #

using System;
using UnityEngine;
using UnityEngine.Tilemaps;
using UnityEngine.Networking;
using System.Collections;
using System.Collections.Generic;
using UnityEditor.VersionControl;

[Serializable]
public class AWSLoginResult
{
    public string timestamp;
    public string level;
    public string requestId;
    public message message; 

}

[Serializable]
public class message
{
    public string ChallangeName;
    public ChallangeParameters ChallangeParameters;
    public string Session;
}

[Serializable]
public class ChallangeParameters
{
    public string USER_ID_FOR_SRP;
    public string userAttributes;
    public string requiredAttributes;

}

问题定位 #

1. 结构不匹配：调试得到的响应是原JSON中message字段的内容（无外层timestamp/level/requestId），但代码中仍用包含外层结构的AWSLoginResult反序列化，导致字段无法映射。
2. 拼写错误：类中ChallangeName/ChallangeParameters与JSON中的ChallengeName/ChallengeParameters拼写不一致（少一个字母e），导致字段无法绑定。
3. 缺失字段定义：调试响应中的metadata字段未在message类中定义，会丢失该部分数据（虽不影响核心字段，但不符合完整解析要求）。

解决方案 #

1. 修正类结构拼写与字段定义 #

using System;
using UnityEngine;

[Serializable]
public class AWSLoginResult
{
    public string timestamp;
    public string level;
    public string requestId;
    public Message message; 
}

[Serializable]
public class Message
{
    public Metadata metadata;
    public string ChallengeName;
    public ChallengeParameters ChallengeParameters;
    public string Session;
}

[Serializable]
public class Metadata
{
    public int httpStatusCode;
    public string requestId;
    public int attempts;
    public int totalRetryDelay;
}

[Serializable]
public class ChallengeParameters
{
    public string USER_ID_FOR_SRP;
    public string userAttributes;
    public string requiredAttributes;
}

2. 调整反序列化目标类 #

根据调试得到的响应结构，实际后端返回的是Message类对应的JSON，因此修改登录代码中的反序列化逻辑：

else {
    // 移除$字符，匹配类中的metadata字段
    string cleanedJson = www.downloadHandler.text.Replace("$", "");
    // 反序列化为Message类而非AWSLoginResult
    Message loginMessage = JsonUtility.FromJson<Message>(cleanedJson);
    Debug.Log(cleanedJson);
    // 打印正确的字段
    Debug.Log(loginMessage.ChallengeName);
}

3. 优化UnityWebRequest调用方式（可选） #

避免用while循环阻塞主线程，改用协程实现异步请求：

public IEnumerator LoginRequest()
{
    AWSUserLoginRequest request = new AWSUserLoginRequest();
    request.username = username;
    request.password = password;

    using (UnityWebRequest www = UnityWebRequest.Post("https://game-api.compassoftruth.org/prod/Login", JsonUtility.ToJson(request), "application/json"))
    {
        yield return www.SendWebRequest();
        
        if (www.result != UnityWebRequest.Result.Success)
        {
            Debug.Log(www.error);
        }
        else
        {
            string cleanedJson = www.downloadHandler.text.Replace("$", "");
            Message loginMessage = JsonUtility.FromJson<Message>(cleanedJson);
            Debug.Log(cleanedJson);
            Debug.Log(loginMessage.ChallengeName);
        }
    }
}

内容的提问来源于stack exchange，提问作者RobloxHero