如何反序列化作为 System.Text.Json 中的字符串的嵌套 JSON 对象？答案

【问题标题】：How do I deserialize a nested JSON object which is a string in System.Text.Json?如何反序列化作为 System.Text.Json 中的字符串的嵌套 JSON 对象？
【发布时间】：2021-11-29 00:30:19
【问题描述】：

我在 ASP.NET 5 MVC 应用程序中反序列化 JSON，使用：

var tulemus = JsonSerializer.Deserialize<EstoJarelMaksTulemnus>(apiResponse, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

public class EstoJarelMaksTulemnus
{
   public string[] Errors { get; set; }
   public EstoData Data { get; set; }
   public string Mac { get; set; }
}

public class EstoData
{
   public string Id { get; set; }
   public string Status { get; set; }
   public string Purchase_url { get; set; }
   public string Merchant_reference { get; set; }
   public decimal Amount { get; set; }
   public string Currency { get; set; }
   public bool Is_test { get; set; }
   public string Return_url { get; set; }
   public string Notification_url { get; set; }
}

这会引发错误：

System.Text.Json.JsonException：无法转换 JSON 值到 Store.Controllers.CheckoutController+EstoData。路径：$.data | 行号：0 | BytePositionInLine: 497. 在 System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue（类型属性类型）...

apiResponse 是一个单行字符串，包含一个嵌入的EstoData：

{"errors":[],"data":"{\"id\":\"iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913\",\"status\":\"CREATED\",\"purchase_url\":\"https:\\\/\\\/user.esto.com\\\/application\\\/iUW3YiDIeO8hV7d3Cv7SVbZ913\",\"merchant_reference\":\"15502\",\"amount\":93.95,\"currency\":\"EUR\",\"is_test\":true,\"return_url\":\"http:\\\/\\\/localhost:54274\\\/CheckoutController\\\/EstoJarelmaksOK?tellimus=104742\",\"notification_url\":\"http:\\\/\\\/localhost:54274\\\/CheckoutController\\\/EstoJarelmaksTeade?tellimus=104742\"}","mac":"E9C3E61FC347D8043ABDCF464D537C37A609EC878F95B5F526271A2287F2D2E507B5A14FA3AF5F7A6D4CDECB6E8A1DBDF9A5633E0B3AD96DA35FA1C9"}

位置 497 似乎指向 Data 属性的末尾，位于 mac 之前。

考虑到 EstoData 在我的对象中是具体的嵌套类型，但在 JSON 中是 string，我如何将此 JSON 反序列化为 EstoJarelMaksTulemnus？

【问题讨论】：

在过去的一周里，我已经看到了十几个关于此的问题。为什么每个人都在编写或使用返回这种格式的 API？

标签： c# asp.net-core asp.net-core-mvc json-deserialization system.text.json

【解决方案1】：

您需要创建一个自定义JsonConverter<T>，在这种情况下T 是EstoData，以便能够正确反序列化嵌套的Data JSON 对象。

这应该可以再次用于反序列化和序列化对象：

StringToEstoDataConverter.cs

public class StringToEstoDataConverter : JsonConverter<EstoData>
{
  public override EstoData? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
  {
      using (var jsonDoc = JsonDocument.ParseValue(ref reader))
      {
          var infoData = jsonDoc.RootElement.GetString();
          if (infoData != null)
              return JsonSerializer.Deserialize<EstoData>(infoData, options);
      }

      return default;
  }

  public override void Write(Utf8JsonWriter writer, EstoData value, JsonSerializerOptions options)
  {
      JsonSerializer.Serialize(writer, value, value.GetType(), options);
  }
}

EstoJarelMaksTulemnus.cs

public class EstoJarelMaksTulemnus
{
  public string[] Errors { get; set; }

  [JsonConverter(typeof(StringToEstoDataConverter))]
  public EstoData Data { get; set; }

  public string Mac { get; set; }
}

用法：

var tulemus = JsonSerializer.Deserialize<EstoJarelMaksTulemnus>(apiResponse, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

这是一个工作演示：

public class Program
{
  public static void Main()
  {
      var data =
          "{\"errors\":[],\"data\":\"{\\\"id\\\":\\\"iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913\\\",\\\"status\\\":\\\"CREATED\\\",\\\"purchase_url\\\":\\\"https:\\\\\\/\\\\\\/user.esto.ee\\\\\\/application\\\\\\/iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913\\\",\\\"merchant_reference\\\":\\\"158502\\\",\\\"amount\\\":93.95,\\\"currency\\\":\\\"EUR\\\",\\\"is_test\\\":true,\\\"return_url\\\":\\\"http:\\\\\\/\\\\\\/localhost:54274\\\\\\/CheckoutController\\\\\\/EstoJarelmaksOK?tellimus=104742\\\",\\\"notification_url\\\":\\\"http:\\\\\\/\\\\\\/localhost:54274\\\\\\/CheckoutController\\\\\\/EstoJarelmaksTeade?tellimus=104742\\\"}\",\"mac\":\"E9C3E61FC347D80200F542C43ABDCF464D537C37A609EC878F95B5F526271A2287F2D2E507B5A14FA3AF5F7A6D4CDECB6E8A1DBDF9A5633E0B3AD96DA35FA1C9\"}";


      var tulemus = JsonSerializer.Deserialize<EstoJarelMaksTulemnus>(data, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

      Console.WriteLine(tulemus.Errors.Length);
      Console.WriteLine(tulemus.Data.Id);
      Console.WriteLine(tulemus.Data.Status);
      Console.WriteLine(tulemus.Data.Purchase_url);
      Console.WriteLine(tulemus.Data.Merchant_reference);
      Console.WriteLine(tulemus.Data.Amount);
      Console.WriteLine(tulemus.Data.Currency);
      Console.WriteLine(tulemus.Data.Is_test);
      Console.WriteLine(tulemus.Data.Return_url);
      Console.WriteLine(tulemus.Data.Notification_url);
      Console.WriteLine(tulemus.Mac);
  }
}

public class StringToEstoDataConverter : JsonConverter<EstoData>
{
  public override EstoData? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
  {
      using (var jsonDoc = JsonDocument.ParseValue(ref reader))
      {
          var infoData = jsonDoc.RootElement.GetString();
          if (infoData != null)
              return JsonSerializer.Deserialize<EstoData>(infoData, options);
      }

      return default;
  }

  public override void Write(Utf8JsonWriter writer, EstoData value, JsonSerializerOptions options)
  {
      JsonSerializer.Serialize(writer, value, value.GetType(), options);
  }
}


public class EstoJarelMaksTulemnus
{
  public string[] Errors { get; set; }

  [JsonConverter(typeof(StringToEstoDataConverter))]
  public EstoData Data { get; set; }

  public string Mac { get; set; }
}

public class EstoData
{
  public string Id { get; set; }
  public string Status { get; set; }
  public string Purchase_url { get; set; }
  public string Merchant_reference { get; set; }
  public decimal Amount { get; set; }
  public string Currency { get; set; }
  public bool Is_test { get; set; }
  public string Return_url { get; set; }
  public string Notification_url { get; set; }
}

输出：

0
iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913
CREATED
https://user.esto.ee/application/iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913
158502
93.95
EUR
True
http://localhost:54274/CheckoutController/EstoJarelmaksOK?tellimus=104742
http://localhost:54274/CheckoutController/EstoJarelmaksTeade?tellimus=104742
E9C3E61FC347D80200F542C43ABDCF464D537C37A609EC878F95B5F526271A2287F2D2E507B5A14FA3AF5F7A6D4CDECB6E8A1DBDF9A5633E0B3AD96DA35FA1C9

【讨论】：

【解决方案2】：

你的原始json中的“data”属性是双重序列化的，所以它应该第二次从json字符串反序列化为对象

所以试试这段代码

var json=...your json;

var jd = JsonSerializer.Deserialize<Root>(json, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

// the second deserialize data property from json string to instance
var jdd= JsonSerializer.Deserialize<Data>(jd.data);

JsonDeserialized result = new JsonDeserialized {errors=jd.errors, data=jdd, mac=jd.mac};

var jsonFixed=JsonSerializer.Serialize(result);

固定的json

{
  "errors": [],
  "data": {
    "id": "iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913",
    "status": "CREATED",
    "purchase_url": "https://user.esto.ee/application/iUW3YiDIz5Ahg5eO8hV7d3Cv7SVbZ913",
    "merchant_reference": "158502",
    "amount": 93.95,
    "currency": "EUR",
    "is_test": true,
    "return_url": "http://localhost:54274/CheckoutController/EstoJarelmaksOK?tellimus=104742",
    "notification_url": "http://localhost:54274/CheckoutController/EstoJarelmaksTeade?tellimus=104742"
  },
  "mac": "E9C3E61FC347D80200F542C43ABDCF464D537C37A609EC878F95B5F526271A2287F2D2E507B5A14FA3AF5F7A6D4CDECB6E8A1DBDF9A5633E0B3AD96DA35FA1C9"
}

测试

JsonDeserialized deserializedFixedJson = Deserialize<JsonDeserialized>(jsonFixed, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });

类

public class JsonDeserialized
{
    public List<object> errors { get; set; }
    public Data data { get; set; }
    public string mac { get; set; }
}
public class Data
{
    public string id { get; set; }
    public string status { get; set; }
    public string purchase_url { get; set; }
    public string merchant_reference { get; set; }
    public double amount { get; set; }
    public string currency { get; set; }
    public bool is_test { get; set; }
    public string return_url { get; set; }
    public string notification_url { get; set; }
}
public class Root
{
    public List<object> errors { get; set; }
    public string data { get; set; }
    public string mac { get; set; }
}

【讨论】：

【解决方案3】：

apiResponse 中的Data 不是对象，它是一个字符串，您可以使用Newtonsoft Json.Net 将字符串转换为模型，如本期所述：Deserializing stringified (quote enclosed) nested objects with Newtonsoft Json.Net

【讨论】：

应用程序当前仅使用 .NET5 JsonSerializer。在同一个应用程序中使用两个序列化器是否合理，或者可以使用 .NET 自己的 Deserializer 解决吗？
@Andrus 在两者之间使用临时对象或使用我在下面概述的 JsonConverter 是可行的 - 您可以使用 2 个序列化程序，但在这种情况下，这将是矫枉过正