C# 在JSON.NET中强制转换反序列化接口

我正在尝试建立一个阅读器，它将从各种网站（比如信息抓取）接收JSON对象，并将它们转换为C#对象。我目前正在使用JSON.NET进行反序列化过程。我遇到的问题是，它不知道如何处理类中的接口级属性。这是自然现象：

public IThingy Thing

将产生以下错误：

无法创建I类型的实例。类型是接口或抽象类，无法实例化

它是一个相对重要的东西，而不是一个东西，因为我正在工作的代码被认为是敏感的，单元测试是非常重要的。对于像Thingy这样成熟的对象，不可能为原子测试脚本模拟对象。它们必须是一个接口

我已经仔细阅读了JSON.NET的文档一段时间了，我在这个网站上找到的与此相关的问题都是一年前提出的。有什么帮助吗

---

另外，如果有必要的话，我的应用程序是用.NET 4.0编写的。

任何对象都不会成为i，因为接口都是抽象的

首先序列化的对象是某种具体类型的对象，实现了抽象接口。您需要使用相同的具体类来恢复序列化数据

然后，生成的对象将是实现您正在寻找的抽象接口的某种类型

从中可以看出，您可以使用

(Thingy)JsonConvert.DeserializeObject(jsonString, typeof(Thingy));

---

当反序列化以通知JSON.NET具体类型时。

没有对象将成为一个IThingy，因为接口根据定义都是抽象的

首先序列化的对象是某种具体类型的对象，实现了抽象接口。您需要使用相同的具体类来恢复序列化数据

然后，生成的对象将是实现您正在寻找的抽象接口的某种类型

从中可以看出，您可以使用

(Thingy)JsonConvert.DeserializeObject(jsonString, typeof(Thingy));

---

当反序列化以通知JSON.NET具体类型时。

您可以尝试两件事：

实现一个try/parse模型：

public class Organisation {
  public string Name { get; set; }

  [JsonConverter(typeof(RichDudeConverter))]
  public IPerson Owner { get; set; }
}

public interface IPerson {
  string Name { get; set; }
}

public class Tycoon : IPerson {
  public string Name { get; set; }
}

public class Magnate : IPerson {
  public string Name { get; set; }
  public string IndustryName { get; set; }
}

public class Heir: IPerson {
  public string Name { get; set; }
  public IPerson Benefactor { get; set; }
}

public class RichDudeConverter : JsonConverter
{
  public override bool CanConvert(Type objectType)
  {
    return (objectType == typeof(IPerson));
  }

  public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
  {
    // pseudo-code
    object richDude = serializer.Deserialize<Heir>(reader);

    if (richDude == null)
    {
        richDude = serializer.Deserialize<Magnate>(reader);
    }

    if (richDude == null)
    {
        richDude = serializer.Deserialize<Tycoon>(reader);
    }

    return richDude;
  }

  public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
  {
    // Left as an exercise to the reader :)
    throw new NotImplementedException();
  }
}

公共类组织{
公共字符串名称{get；set；}
[JsonConverter（类型（RichDudeConverter））]
公共IPerson所有者{get；set；}
}
公共接口IPerson{
字符串名称{get；set；}
}
公共阶层大亨：伊佩森{
公共字符串名称{get；set；}
}
公共阶层巨头：伊佩森{
公共字符串名称{get；set；}
公共字符串IndustryName{get；set；}
}
公共类继承人：IPerson{
公共字符串名称{get；set；}
公共IPerson施主{get；set；}
}
公共类转换器：JsonConverter
{
公共覆盖布尔CanConvert（类型objectType）
{
返回（objectType==typeof（IPerson））；
}
公共重写对象ReadJson（JsonReader阅读器，类型objectType，对象existingValue，JsonSerializer序列化程序）
{
//伪码
object richDude=序列化程序。反序列化（读取器）；
if（richDude==null）
{
richDude=序列化程序。反序列化（读取器）；
}
if（richDude==null）
{
richDude=序列化程序。反序列化（读取器）；
}
返回里奇杜德；
}
公共重写void WriteJson（JsonWriter编写器、对象值、JsonSerializer序列化器）
{
//留给读者作为练习：）
抛出新的NotImplementedException（）；
}
}

或者，如果可以在对象模型中这样做，则在IPerson和叶对象之间实现一个具体的基类，并反序列化到它

---

第一种方法可能在运行时失败，第二种方法需要更改对象模型，并将输出均匀化为最低公分母。

您可以尝试以下两种方法：

实现一个try/parse模型：

public class Organisation {
  public string Name { get; set; }

  [JsonConverter(typeof(RichDudeConverter))]
  public IPerson Owner { get; set; }
}

public interface IPerson {
  string Name { get; set; }
}

public class Tycoon : IPerson {
  public string Name { get; set; }
}

public class Magnate : IPerson {
  public string Name { get; set; }
  public string IndustryName { get; set; }
}

public class Heir: IPerson {
  public string Name { get; set; }
  public IPerson Benefactor { get; set; }
}

public class RichDudeConverter : JsonConverter
{
  public override bool CanConvert(Type objectType)
  {
    return (objectType == typeof(IPerson));
  }

  public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
  {
    // pseudo-code
    object richDude = serializer.Deserialize<Heir>(reader);

    if (richDude == null)
    {
        richDude = serializer.Deserialize<Magnate>(reader);
    }

    if (richDude == null)
    {
        richDude = serializer.Deserialize<Tycoon>(reader);
    }

    return richDude;
  }

  public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
  {
    // Left as an exercise to the reader :)
    throw new NotImplementedException();
  }
}

公共类组织{
公共字符串名称{get；set；}
[JsonConverter（类型（RichDudeConverter））]
公共IPerson所有者{get；set；}
}
公共接口IPerson{
字符串名称{get；set；}
}
公共阶层大亨：伊佩森{
公共字符串名称{get；set；}
}
公共阶层巨头：伊佩森{
公共字符串名称{get；set；}
公共字符串IndustryName{get；set；}
}
公共类继承人：IPerson{
公共字符串名称{get；set；}
公共IPerson施主{get；set；}
}
公共类转换器：JsonConverter
{
公共覆盖布尔CanConvert（类型objectType）
{
返回（objectType==typeof（IPerson））；
}
公共重写对象ReadJson（JsonReader阅读器，类型objectType，对象existingValue，JsonSerializer序列化程序）
{
//伪码
object richDude=序列化程序。反序列化（读取器）；
if（richDude==null）
{
richDude=序列化程序。反序列化（读取器）；
}
if（richDude==null）
{
richDude=序列化程序。反序列化（读取器）；
}
返回里奇杜德；
}
公共重写void WriteJson（JsonWriter编写器、对象值、JsonSerializer序列化器）
{
//留给读者作为练习：）
抛出新的NotImplementedException（）；
}
}

或者，如果可以在对象模型中这样做，则在IPerson和叶对象之间实现一个具体的基类，并反序列化到它

---

第一种可能在运行时失败，第二种可能需要更改对象模型并将输出均匀化为最低公分母。

无论如何，我最终不得不自己处理这一问题。每个对象都有一个反序列化（stringjsonstream）方法。其中的几个片段：

JObject parsedJson = this.ParseJson(jsonStream);
object thingyObjectJson = (object)parsedJson["thing"];
this.Thing = new Thingy(Convert.ToString(thingyObjectJson));

在本例中，newthingy（string）是一个构造函数，它将调用相应具体类型的反序列化（stringjsonstream）方法。此方案将继续向下，直到您到达json.NET可以处理的基点为止

this.Name = (string)parsedJson["name"];
this.CreatedTime = DateTime.Parse((string)parsedJson["created_time"]);

诸如此类。这个设置允许我提供它可以处理的json.NET设置，而无需重构库本身的很大一部分，也无需使用笨拙的try/parse模型

Newtonsoft.Json.JsonSerializer serializer = new Newtonsoft.Json.JsonSerializer();
serializer.Converters.Add(new DTOJsonConverter());
Interfaces.IEntity entity = serializer.Deserialize(jsonReader);

class DTOJsonConverter : Newtonsoft.Json.JsonConverter
{
    private static readonly string ISCALAR_FULLNAME = typeof(Interfaces.IScalar).FullName;
    private static readonly string IENTITY_FULLNAME = typeof(Interfaces.IEntity).FullName;


    public override bool CanConvert(Type objectType)
    {
        if (objectType.FullName == ISCALAR_FULLNAME
            || objectType.FullName == IENTITY_FULLNAME)
        {
            return true;
        }
        return false;
    }

    public override object ReadJson(Newtonsoft.Json.JsonReader reader, Type objectType, object existingValue, Newtonsoft.Json.JsonSerializer serializer)
    {
        if (objectType.FullName == ISCALAR_FULLNAME)
            return serializer.Deserialize(reader, typeof(DTO.ClientScalar));
        else if (objectType.FullName == IENTITY_FULLNAME)
            return serializer.Deserialize(reader, typeof(DTO.ClientEntity));

        throw new NotSupportedException(string.Format("Type {0} unexpected.", objectType));
    }

    public override void WriteJson(Newtonsoft.Json.JsonWriter writer, object value, Newtonsoft.Json.JsonSerializer serializer)
    {
        serializer.Serialize(writer, value);
    }
}

public class Visit : IVisit
{
    /// <summary>
    /// This constructor is required for the JSON deserializer to be able
    /// to identify concrete classes to use when deserializing the interface properties.
    /// </summary>
    public Visit(MyLocation location, Guest guest)
    {
        Location = location;
        Guest = guest;
    }
    public long VisitId { get; set; }
    public ILocation Location { get;  set; }
    public DateTime VisitDate { get; set; }
    public IGuest Guest { get; set; }
}

public class ConcreteListTypeConverter<TInterface, TImplementation> : JsonConverter where TImplementation : TInterface 
{
    public override bool CanConvert(Type objectType)
    {
        return true;
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var res = serializer.Deserialize<List<TImplementation>>(reader);
        return res.ConvertAll(x => (TInterface) x);
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        serializer.Serialize(writer, value);
    }
}

/// <summary>
/// Automagically convert known interfaces to (specific) concrete classes on deserialisation
/// </summary>
public class WithMocksJsonConverter : JsonConverter
{
    /// <summary>
    /// The interfaces I know how to instantiate mapped to the classes with which I shall instantiate them, as a Dictionary.
    /// </summary>
    private readonly Dictionary<Type,Type> conversions = new Dictionary<Type,Type>() { 
        { typeof(IOne), typeof(MockOne) },
        { typeof(ITwo), typeof(MockTwo) },
        { typeof(IThree), typeof(MockThree) },
        { typeof(IFour), typeof(MockFour) }
    };

    /// <summary>
    /// Can I convert an object of this type?
    /// </summary>
    /// <param name="objectType">The type under consideration</param>
    /// <returns>True if I can convert the type under consideration, else false.</returns>
    public override bool CanConvert(Type objectType)
    {
        return conversions.Keys.Contains(objectType);
    }

    /// <summary>
    /// Attempt to read an object of the specified type from this reader.
    /// </summary>
    /// <param name="reader">The reader from which I read.</param>
    /// <param name="objectType">The type of object I'm trying to read, anticipated to be one I can convert.</param>
    /// <param name="existingValue">The existing value of the object being read.</param>
    /// <param name="serializer">The serializer invoking this request.</param>
    /// <returns>An object of the type into which I convert the specified objectType.</returns>
    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        try
        {
            return serializer.Deserialize(reader, this.conversions[objectType]);
        }
        catch (Exception)
        {
            throw new NotSupportedException(string.Format("Type {0} unexpected.", objectType));
        }
    }

    /// <summary>
    /// Not yet implemented.
    /// </summary>
    /// <param name="writer">The writer to which I would write.</param>
    /// <param name="value">The value I am attempting to write.</param>
    /// <param name="serializer">the serializer invoking this request.</param>
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

public class Parent
{
    [JsonConverter(typeof(InterfaceConverter<IChildModel, ChildModel>))]
    IChildModel Child { get; set; }
}

public class InterfaceConverter<TInterface, TConcrete> : CustomCreationConverter<TInterface>
    where TConcrete : TInterface, new()
{
    public override TInterface Create(Type objectType)
    {
        return new TConcrete();
    }
}

JsonConvert.SerializeObject(
  toSerialize,
  new JsonSerializerSettings()
  {
    TypeNameHandling = TypeNameHandling.Auto
  });

public class AutofacContractResolver : DefaultContractResolver
{
    private readonly IContainer _container;

    public AutofacContractResolver(IContainer container)
    {
        _container = container;
    }

    protected override JsonObjectContract CreateObjectContract(Type objectType)
    {
        JsonObjectContract contract = base.CreateObjectContract(objectType);

        // use Autofac to create types that have been registered with it
        if (_container.IsRegistered(objectType))
        {
           contract.DefaultCreator = () => _container.Resolve(objectType);
        }  

        return contract;
    }
}

public class TaskController
{
    private readonly ITaskRepository _repository;
    private readonly ILogger _logger;

    public TaskController(ITaskRepository repository, ILogger logger)
    {
        _repository = repository;
        _logger = logger;
    }

    public ITaskRepository Repository
    {
        get { return _repository; }
    }

    public ILogger Logger
    {
        get { return _logger; }
    }
}

ContainerBuilder builder = new ContainerBuilder();
builder.RegisterType<TaskRepository>().As<ITaskRepository>();
builder.RegisterType<TaskController>();
builder.Register(c => new LogService(new DateTime(2000, 12, 12))).As<ILogger>();

IContainer container = builder.Build();

AutofacContractResolver contractResolver = new AutofacContractResolver(container);

string json = @"{
      'Logger': {
        'Level':'Debug'
      }
}";

// ITaskRespository and ILogger constructor parameters are injected by Autofac 
TaskController controller = JsonConvert.DeserializeObject<TaskController>(json, new JsonSerializerSettings
{
    ContractResolver = contractResolver
});

Console.WriteLine(controller.Repository.GetType().Name);

using Castle.DynamicProxy;
using Newtonsoft.Json.Linq;
using System;
using System.Reflection;

namespace LL.Utilities.Std.Json
{
    public static class JObjectExtension
    {
        private static ProxyGenerator _generator = new ProxyGenerator();

        public static dynamic toProxy(this JObject targetObject, Type interfaceType) 
        {
            return _generator.CreateInterfaceProxyWithoutTarget(interfaceType, new JObjectInterceptor(targetObject));
        }

        public static InterfaceType toProxy<InterfaceType>(this JObject targetObject)
        {

            return toProxy(targetObject, typeof(InterfaceType));
        }
    }

    [Serializable]
    public class JObjectInterceptor : IInterceptor
    {
        private JObject _target;

        public JObjectInterceptor(JObject target)
        {
            _target = target;
        }
        public void Intercept(IInvocation invocation)
        {

            var methodName = invocation.Method.Name;
            if(invocation.Method.IsSpecialName && methodName.StartsWith("get_"))
            {
                var returnType = invocation.Method.ReturnType;
                methodName = methodName.Substring(4);

                if (_target == null || _target[methodName] == null)
                {
                    if (returnType.GetTypeInfo().IsPrimitive || returnType.Equals(typeof(string)))
                    {

                        invocation.ReturnValue = null;
                        return;
                    }

                }

                if (returnType.GetTypeInfo().IsPrimitive || returnType.Equals(typeof(string)))
                {
                    invocation.ReturnValue = _target[methodName].ToObject(returnType);
                }
                else
                {
                    invocation.ReturnValue = ((JObject)_target[methodName]).toProxy(returnType);
                }
            }
            else
            {
                throw new NotImplementedException("Only get accessors are implemented in proxy");
            }

        }
    }



}

var jObj = JObject.Parse(input);
InterfaceType proxyObject = jObj.toProxy<InterfaceType>();

public class Customer: ICustomer{
     public Customer(Details details){
          Details = details;
     }

     [JsonProperty("Details",NullValueHnadling = NullValueHandling.Ignore)]
     public IDetails Details {get; set;}
}

public class Person
{
    public IProfession Profession { get; set; }
}

public interface IProfession
{
    string JobTitle { get; }
}

public class Programming : IProfession
{
    public string JobTitle => "Software Developer";
    public string FavoriteLanguage { get; set; }
}

public class Writing : IProfession
{
    public string JobTitle => "Copywriter";
    public string FavoriteWord { get; set; }
}

public class Samples
{
    public static Person GetProgrammer()
    {
        return new Person()
        {
            Profession = new Programming()
            {
                FavoriteLanguage = "C#"
            }
        };
    }
}

public class ProfessionConverter : JsonConverter
{
    public override bool CanWrite => false;
    public override bool CanRead => true;
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(IProfession);
    }
    public override void WriteJson(JsonWriter writer,
        object value, JsonSerializer serializer)
    {
        throw new InvalidOperationException("Use default serialization.");
    }

    public override object ReadJson(JsonReader reader,
        Type objectType, object existingValue,
        JsonSerializer serializer)
    {
        var jsonObject = JObject.Load(reader);
        var profession = default(IProfession);
        switch (jsonObject["JobTitle"].Value())
        {
            case "Software Developer":
                profession = new Programming();
                break;
            case "Copywriter":
                profession = new Writing();
                break;
        }
        serializer.Populate(jsonObject.CreateReader(), profession);
        return profession;
    }
}

    public class Person
    {
        [JsonConverter(typeof(ProfessionConverter))]
        public IProfession Profession { get; set; }
    }

Person person = JsonConvert.DeserializeObject<Person>(jsonString);

[JsonConverter(typeof(JsonKnownTypeConverter<Interface1>))]
[JsonKnownType(typeof(MyClass), "myClass")]
public interface Interface1
{  }
public class MyClass : Interface1
{
    public string Something;
}

{"Something":"something", "$type":"derived"}