c# - 在 Newtonsoft.Json 中反序列化自定义异常

Question

我在反序列化 Newtonsoft.Json 版本 11.0.2 中的自定义异常时遇到了问题。它在 Newtonsoft.Json 版本 10.0.3 中运行良好。

我序列化和反序列化使用 -

result = JsonConvert.SerializeObject( <<object of type MyHttpException>> );
MyHttpException deserializedException = JsonConvert.DeserializeObject<MyHttpException>(result);

我在反序列化期间遇到的错误是 Newtonsoft.Json.JsonSerializationException:

Unable to find a constructor to use for type MyHttpException. A class should either have a default constructor, one constructor with arguments or a constructor marked with the JsonConstructor attribute. Path 'HttpStatusCode', line 2, position 19.

如果我向 MyHttpException 和 MyBaseException 添加一个无参数构造函数，我不会得到任何异常。但是 InnerException 没有被反序列化并且为 null。

有什么明显的我遗漏的东西吗？我不确定为什么这会在 10.0.3 中工作并在 11.0.2 中中断。

我的异常类——

public sealed class MyHttpException : MyBaseException
{
    public MyHttpException(HttpStatusCode httpStatusCode, int MyStatusCode)
        : base(MyStatusCode) => HttpStatusCode = httpStatusCode;

    public MyHttpException(HttpStatusCode httpStatusCode, int MyStatusCode, string message)
        : base(MyStatusCode, message) => HttpStatusCode = httpStatusCode;

    public MyHttpException(HttpStatusCode httpStatusCode, int MyStatusCode, Exception innerException)
        : base(MyStatusCode, innerException) => HttpStatusCode = httpStatusCode;

    public MyHttpException(HttpStatusCode httpStatusCode, int MyStatusCode, string message, Exception innerException)
        : base(MyStatusCode, message, innerException) => HttpStatusCode = httpStatusCode;

    [SecurityPermission(SecurityAction.Demand, SerializationFormatter = true)]
    private MyHttpException(SerializationInfo info, StreamingContext context)
        : base(info, context) => HttpStatusCode = (HttpStatusCode)info.GetValue("HttpStatusCode", typeof(HttpStatusCode));

    public HttpStatusCode HttpStatusCode { get; set; }

    [SecurityPermission(SecurityAction.Demand, SerializationFormatter = true)]
    public override void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (info == null)
        {
            throw new ArgumentNullException("info");
        }

        info.AddValue("HttpStatusCode", HttpStatusCode);

        // MUST call through to the base class to let it save its own state
        base.GetObjectData(info, context);
    }
}

public abstract class MyBaseException : Exception
{
    public MyBaseException(int MyStatusCode) => this.MyStatusCode = MyStatusCode;

    public MyBaseException(int MyStatusCode, string message)
        : base(message) => this.MyStatusCode = MyStatusCode;

    public MyBaseException(int MyStatusCode, Exception innerException)
        : base("MyErrorCode: " + MyStatusCode + ". " + MyStatusCodes.GetDescription(MyStatusCode) + ". " + innerException.Message, innerException) => this.MyStatusCode = MyStatusCode;

    public MyBaseException(int MyStatusCode, string message, Exception innerException)
        : base(message, innerException) => this.MyStatusCode = MyStatusCode;

    [SecurityPermission(SecurityAction.Demand, SerializationFormatter = true)]
    protected MyBaseException(SerializationInfo info, StreamingContext context)
        : base(info, context)
    {
        MyStatusCode = info.GetInt32("MyStatusCode");
    }

    public int MyStatusCode { get; set; }

    [SecurityPermission(SecurityAction.Demand, SerializationFormatter = true)]
    public override void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (info == null)
        {
            throw new ArgumentNullException("info");
        }

        info.AddValue("MyStatusCode", MyStatusCode);

        // MUST call through to the base class to let it save its own state
        base.GetObjectData(info, context);
    }
}

谢谢

Answer 1

在 Json.NET 11 中，ISerializable 类型的序列化方式发生了变化。根据release notes :

• Change - Types that implement ISerializable but don't have [SerializableAttribute] are not serialized using ISerializable

因此，您现在必须用 SerializableAttribute 标记您的异常类型:

[Serializable]
public sealed class MyHttpException : MyBaseException
{
}

[Serializable]
public abstract class MyBaseException : Exception
{
}

或者，您可以创建一个 custom contract resolver恢复旧行为:

public class PreferISerializableContractResolver : DefaultContractResolver
{
    protected override JsonContract CreateContract(Type objectType)
    {
        var contract = base.CreateContract(objectType);

        if (!IgnoreSerializableInterface
            && contract is JsonObjectContract
            && typeof(ISerializable).IsAssignableFrom(objectType)
            && !objectType.GetCustomAttributes(true).OfType<JsonContainerAttribute>().Any())
        {
            contract = CreateISerializableContract(objectType);
        }

        return contract;
    }
}

(您可能想要 cache the contract resolver for best performance 。)

为什么要进行此更改？根据Issue #1622: classes deriving from System.Exception do not serialize/deserialize properly :

Json.NET previous wasn't serializing ISerializable types correctly. The SerializableAttribute is required.

See here for more info dotnet/corefx#23415.

然后是链接问题 dotnet/corefx Issue #23415: PlatformNotSupportedException when attempting to serialize DirectoryInfo instance with Newtonsoft.Json表示更改是应 .NET Core 团队的要求进行的:

JamesNK commented on Aug 29, 2017

So the issue is Json.NET is checking that a type implements ISerializable but not also checking for the SerialiazableAttribute?

ViktorHofer commented on Aug 29, 2017

Correct :)

因此，如果您使用 PreferISerializableContractResolver 而不是使用 [Serializable] 标记您的 ISerializable 类型，您可能会在 .NET 中遇到这个问题核心。