反序列化可在相同属性名称下包含不同对象的JSON

VBobCat 发表于 Dev

VBobCat

我正在使用JSON.NET来反序列化来自HTTP查询的JSON响应，但是我遇到了一个问题。这是因为响应可以在相同属性下发送两种类型的对象，如下所示：

第一种情况样本（最常见）：

{
  "type": "myType",
  "tid": 4,
  "action": "myAction",
  "method": "myMethod",
  "result": {
    "success": true,
    "total": 4,
    "records": [
      {
        "id": 4,
        "nome": "PRIMEIRO NOME",
        "sigla": "PN"
      },
      {
        "id": 1974,
        "nome": "SEGUNDO NOME",
        "sigla": "SN"
      },
      {
        "id": 2584,
        "nome": "TERCEIRO NOME",
        "sigla": "TN"
      },
      {
        "id": 1170,
        "nome": "QUARTO NOME",
        "sigla": "QN"
      }
    ]
  }
}

第二例样品（稀有）：

{
  "type": "myType",
  "tid": 3,
  "action": "myAction",
  "method": "myMethod",
  "result": [
    {
      "id": 4,
      "nome": "PRIMEIRO NOME",
      "sigla": "PN"
    },
    {
      "id": 1974,
      "nome": "SEGUNDO NOME",
      "sigla": "SN"
    },
    {
      "id": 2584,
      "nome": "TERCEIRO NOME",
      "sigla": "TN"
    },
    {
      "id": 1170,
      "nome": "QUARTO NOME",
      "sigla": "QN"
    }
  ]
}

我一直在使用这些类来接收第一种情况的数据：

Public Class Record
    Public Property id As Integer
    Public Property nome As String
    Public Property sigla As String
End Class

Public Class Result
    Public Property success As Boolean
    Public Property total As Integer
    Public Property records As Record()
End Class

Public Class Response
    Public Property type As String
    Public Property tid As Integer
    Public Property action As String
    Public Property method As String
    Public Property result As Result
End Class

因此，在使用以下语句对第一种情况JSON反序列化时，它可以很好地工作：

Dim myResponse = JsonConvert.DeserializeObject(Of Response)(myJsonString)

但是，当接收第二种情况JSON时，它将创建类型为Response的对象，在其属性结果中存储类型为Result的对象，该对象的属性保持为空，并且我需要为其检索的数据也消失了。

我认为我应该修改Response类，以便通过以下方式为不同的数据集放置位置：

Public Class Response
    Public Property type As String
    Public Property tid As Integer
    Public Property action As String
    Public Property method As String
    Public Property result As Result
    Public Property resultRecords As Record()
End Class

那么，问题是：我该如何告诉JsonConvert是将数据存储在适合其类型的属性Response.result中（上面的第一个示例），还是将响应存储在Response.resultRecords中？

谢谢！

布莱恩·罗杰斯（Brian Rogers）

由于JSON的格式对于同一属性可能有所不同，因此您将需要一个自定义样式JsonConverter来处理它。转换器可以读取受影响属性的JSON，确定其格式，然后适当地填充您的对象。这是您需要的代码：

Public Class ResultConverter
    Inherits JsonConverter

    Public Overrides Function CanConvert(objectType As Type) As Boolean
        Return objectType = GetType(Result)
    End Function

    Public Overrides Function ReadJson(reader As JsonReader, objectType As Type, existingValue As Object, serializer As JsonSerializer) As Object
        Dim token As JToken = JToken.Load(reader)
        Dim result As Result = New Result
        If token.Type = JTokenType.Array Then
            result.records = token.ToObject(Of Record())(serializer)
            result.total = result.records.Length
            result.success = True
        Else
            serializer.Populate(token.CreateReader(), result)
        End If
        Return result
    End Function

    Public Overrides ReadOnly Property CanWrite As Boolean
        Get
            Return False
        End Get
    End Property

    Public Overrides Sub WriteJson(writer As JsonWriter, value As Object, serializer As JsonSerializer)
        Throw New NotImplementedException
    End Sub
End Class

要使用转换器，请在类<JsonConverter>的result属性中添加一个属性Response：

Public Class Response
    Public Property type As String
    Public Property tid As Integer
    Public Property action As String
    Public Property method As String
    <JsonConverter(GetType(ResultConverter))>
    Public Property result As Result
End Class

这是一个有用的小提琴，它表明此转换器将允许将两种JSON格式反序列化为相同的类：https : //dotnetfiddle.net/NFbQ2Q

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