使用嵌套对象和中间步骤反序列化

Question

我正在尝试 serialize/deserialze 使用 System.Text.Json JsonSerializer 的对象。我的容器对象是一个“LicenseFile”，它包含一个“License”对象和一个 byte[] 数字签名。

public class LicenseFile
{
    public License License { get; set; }
    public byte[] Signature { get; set; }
}

public class License
{
    public string ProductName { get; set; }
    public string ProductVersion { get; set; }
}

在序列化 LicenseFile 时，我还想先将 License 值转换为 JSON，然后再转换为 Base64。为此，我创建了一个自定义 JSON 转换器，例如

public class LicenseFileConverter : JsonConverter<LicenseFile>
{
    public override void Write(Utf8JsonWriter writer, LicenseFile licenseFile, JsonSerializerOptions options)
    {
        writer.WriteStartObject();
        var json = JsonSerializer.Serialize(licenseFile.License);
        byte[] jsonBytes = new UTF8Encoding().GetBytes(json);
        writer.WriteBase64String("License", jsonBytes);
        writer.WriteBase64String("Signature", licenseFile.Signature);
        writer.WriteEndObject();
        writer.Flush();
    }
}

我想以这样的 JSON 输出结束：

{
  "License": "BASE64_OF_LICENSE_OBJECT_JSON'D",
  "Signature": "BASE64_OF_SIGNATURE_BYTE[]"
}

我的问题：

这是一个好方法吗？我最好只使用辅助方法先序列化值，对它们进行 base64，然后将它们写到文件中吗？
如何将 JSON 对象再次反序列化为对象（同时对它们进行 de-base64 处理）

感谢您的任何建议！

Answer 1

我推荐：

一个专用的Dto；或
[JsonIgnore] License 和一个辅助字段；

例如：

public class LicenseFile
{
    [JsonIgnore]
    public License License { get; set; }

    public string LicenseJson => JsonSerializer.Serialize(License); // Add base64 encoding if you wish

    public byte[] Signature { get; set; }
}

或

public class LicenseFileDto
{
    public LicenseFileDto(LicenseFile license) {
        License = JsonSerializer.Serialize(license.License);
        Signature = license.Signature;
    }
    public string License { get; }
    public byte[] Signature { get; }
}

测试

var l = new LicenseFile
{
    License = new License(name: "X Y", validUntil: new DateTime(2021, 04, 22)),
    Signature = new byte[] { 1, 2, 3 }
};

var json = JsonSerializer.Serialize(l, 
    options: new JsonSerializerOptions { WriteIndented = true });
Console.WriteLine(json);

var dtoJson = JsonSerializer.Serialize(new LicenseFileDto(l), 
    options: new JsonSerializerOptions { WriteIndented = true });
Console.WriteLine(dtoJson);            

// Documentation at:
//   https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-character-encoding#serialize-all-characters
// says: 
//     Use the unsafe encoder only when it's known that the client will be interpreting the resulting payload as UTF-8 encoded JSON.
var prettyJson = JsonSerializer.Serialize(new LicenseFileDto(l), 
    options: new JsonSerializerOptions { WriteIndented = true, Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping });
Console.WriteLine(prettyJson);

{
  "LicenseJson": "{\u0022Name\u0022:\u0022X Y\u0022,\u0022ValidUntil\u0022:\u00222021-04-22T00:00:00\u0022}",
  "Signature": "AQID"
}
{
  "License": "{\u0022Name\u0022:\u0022X Y\u0022,\u0022ValidUntil\u0022:\u00222021-04-22T00:00:00\u0022}",
  "Signature": "AQID"
}
{
  "License": "{\"Name\":\"X Y\",\"ValidUntil\":\"2021-04-22T00:00:00\"}",
  "Signature": "AQID"
}

使用嵌套对象和中间步骤反序列化

Deserialization with nested object and in-between step

c#

base64

jsonserializer

system.text.json

测试