JSON.NET反序列化为具有Type参数的对象 [英] JSON.NET deserialize to object with Type parameter

问题描述

我有以下问题，我无法解决：

我有不同的类，它们都实现一个名为 IProtocol 。现在，命名为 SimpleProtocol ， ParallelProtocol 。我想坚持那些对象，所以我使用JSON.NET和一切工作正常。除非我试图反序列化它们，当我知道它们应该是什么类型时，它工作完美，例如：

  SimpleProtocol p = JsonConvert.DeserializeObject< SimpleProtocol>（myJsonData）; 
  

然而，我现在处于一种情况，我想加载JSON数据，并获得 IProtocol 回来，但这是可以理解的，JSON不允许;例如，类似这样的东西不工作：

  IProtocol p1 = JsonConvert.DeserializeObject< IProtocol> myJsonData）; //不工作
 IProtocol p2 =（IProtocol）JsonConvert.DeserializeObject（myJsonData）; //也不工作
  

因此，查找 API 我发现此方法签名：

  public static Object DeserializeObject（
 string value，
 Type type 
）
  

看起来就像我需要的东西，所以尝试通过在字符串中持久化类型并检索它：

  // test 
类型protocolType = Type.GetType（MyApp.Protocols.SimpleProtocol）; 
 IProtocol p1 = JsonConvert.DeserializeObject（myJsonData，protocolType）; 
  

我得到一个错误，不能投射 Newtonsoft.Json。 Linq.JObject 到 IProtocol 。这是奇怪的，我不知道如何解决这个。

在一个通用的方法是不可能传递Type对象，所以我基本上被困在这里。有没有办法解决这个问题，最好不使用反射？它看起来对我来说是一个完全正常的用例。

我能做什么，但它似乎有点脏我是，创建一个简单的包装器类中包含一个IP协议实例，并序列化/反序列化？

解决方案

似乎我的初始方法是使用这种方法正确的：

  public static Object DeserializeObject（
字符串值，
类型类型
 ）
  

问题是，我坚持我的对象类型为 MyProtocol.GetType （PersistedTypeString）;

$ <$>

/ code>

为具有 null 值的类型。但是使用 MyProtocol.GetType（）。AssemblyQualifiedName 一切都很好（ps这也包括在Type.GetType（）的文档）

这是我的代码示例：

 类型ProtocolType = Type.GetType（MetaData [ProtocolType ]）; 
 var Protocol = JsonConvert.DeserializeObject（Data [Protocol]，ProtocolType，JsonProtocolPersister.DefaultSettings）; 
 return（IProtocol）Protocol; 
  

I have the following problem which I am unable to solve:

I have different classes which all implement an interface named IProtocol. The are named, for now, SimpleProtocol, ParallelProtocol. I wanted to persist those object so I used JSON.NET and everything works fine. Except when I am trying to deserialize them it works perfectly when I know the type they are supposed to be, for instance:

SimpleProtocol p = JsonConvert.DeserializeObject<SimpleProtocol>(myJsonData);

However, I am now in a situation where I want to load the JSON data and get an IProtocol back, but that is, understandably, not allowed by JSON; E.g., something like this does not work:

IProtocol p1 = JsonConvert.DeserializeObject<IProtocol>(myJsonData); // does not work
IProtocol p2 = (IProtocol)JsonConvert.DeserializeObject(myJsonData); // also, does not work

So, looking up the API I found this method signature:

public static Object DeserializeObject(
    string value,
    Type type
)

which looks just like the thing I needed, so trying out by also persisting the type in a string and retrieving it:

// test
Type protocolType = Type.GetType("MyApp.Protocols.SimpleProtocol");
IProtocol p1 = JsonConvert.DeserializeObject(myJsonData, protocolType);

I get an error that it is impossible to cast a Newtonsoft.Json.Linq.JObject to IProtocol. This is weird and I don't know how to solve this.

It is impossible to pass the Type object in a generic method, so I am basically stuck here. Is there a method to solve this, preferably without using Reflection? It looks to me that this is a perfectly normal use case.

What I can do, but it seems a bit 'dirty' to me, is to create a simple wrapper class which holds an IProtocol instance in it and serialize / deserialize that?

解决方案

It seemed that my initial approach by using this method was correct after all:

public static Object DeserializeObject(
    string value,
    Type type
)

The problem was that I persisted my object type as using MyProtocol.GetType().FullName which resulted in a value following from

Type protocolType = Type.GetType(PersistedTypeString);

to be a Type with null values. However by using MyProtocol.GetType().AssemblyQualifiedName everything works just fine (p.s. this is also included in the docs of Type.GetType())

Here is my code sample:

Type ProtocolType = Type.GetType(MetaData["ProtocolType"]);
var Protocol = JsonConvert.DeserializeObject(Data["Protocol"], ProtocolType, JsonProtocolPersister.DefaultSettings);
return (IProtocol)Protocol;

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