通过 Json $type 约定的 AspNet WebApi 多态参数未反序列化

Question

所以问题来了，我实际上是在 Sitecore 中这样做的，但我非常沮丧，我推出了一个新的样板 WebApi 项目，只是为了找到我的问题。

我的断言是，鉴于以下请求，

/api/Simple/AspNetJsonDeserializing?instance={%20"$type":%20"SimpleWebApi.Controllers.ConcreteTestInstance,%20SimpleWebApi",%20"hostName":%20"google.com"%20}

我应该在我的AspNetJsonDeserializing 操作方法中为ITestInstance 实例获取ConcreteTestInstance 的非空参数值。

但是，我收到以下异常：

无法创建接口的实例。

相反，如果我使用我的 NewtonsoftJsonDeserializing 操作方法，并传递一个 jsonString 并使用 Newtonsoft JsonConvert 显式反序列化它，它将很好地反序列化。

我做错了什么？

这是所有代码

Json

{  
    "$type": "SimpleWebApi.Controllers.ConcreteTestInstance, SimpleWebApi", 
    "hostName": "google.com"  
}

控制器/动作

[JsonInterfaceBindingAndNonDefaultConstructors]
public class SimpleController : ApiController
{
    [System.Web.Http.HttpGet]
    public JsonResult<string> NewtonsoftJsonDeserializing(string jsonString) // [FromUri] ITestInstance instance) //   
    {

        JsonSerializerSettings jsonSerializerSettingForTypeHandling = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.All, ConstructorHandling = ConstructorHandling.AllowNonPublicDefaultConstructor };
        ITestInstance instance = JsonConvert.DeserializeObject<ITestInstance>(jsonString, jsonSerializerSettingForTypeHandling);
        return Json("OK");
    }

    [System.Web.Http.HttpGet]
    public JsonResult<string> AspNetJsonDeserializing([FromUri] ITestInstance instance)
    {
        return Json($"Uri:{((ConcreteTestInstance)instance)._instanceUri}");
    }
}

用于修改 SerializerSettings 的属性

[AttributeUsage(AttributeTargets.Class)]
public class JsonInterfaceBindingAndNonDefaultConstructors : Attribute, IControllerConfiguration
{
    public void Initialize(HttpControllerSettings controllerSettings, HttpControllerDescriptor controllerDescriptor)
    {
        IEnumerable<JsonMediaTypeFormatter> jsonFormatters = controllerSettings.Formatters.OfType<JsonMediaTypeFormatter>();
        foreach (var jsonFormatter in jsonFormatters)
        {
            jsonFormatter.SerializerSettings.ContractResolver = new DefaultContractResolver();  //new JsonContractResolver(new JsonMediaTypeFormatter() {});
            jsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.All;
            jsonFormatter.SerializerSettings.ConstructorHandling = ConstructorHandling.AllowNonPublicDefaultConstructor;
        }
    }
}

界面

public interface ITestInstance
{
}

具体子类

public class ConcreteTestInstance : ITestInstance
{
    private const string SCHEME = "http://";
    private const int PORT = 80;
    private const string API_PATH = "/";
    private const string QUERYSTRING = "";


    public readonly Uri _instanceUri;

    public ConcreteTestInstance(string hostName)
    {
        _instanceUri = new UriBuilder(SCHEME, hostName, PORT, API_PATH, QUERYSTRING).Uri;
    }
}

异常：无法创建接口实例。

<Error>
<Message>An error has occurred.</Message>
<ExceptionMessage>Cannot create an instance of an interface.</ExceptionMessage>
<ExceptionType>System.MissingMethodException</ExceptionType>
<StackTrace>
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) at System.Activator.CreateInstance(Type type, Boolean nonPublic) at System.Activator.CreateInstance(Type type) at System.Web.Http.ModelBinding.Binders.MutableObjectModelBinder.CreateModel(HttpActionContext actionContext, ModelBindingContext bindingContext) at System.Web.Http.ModelBinding.Binders.MutableObjectModelBinder.EnsureModel(HttpActionContext actionContext, ModelBindingContext bindingContext) at System.Web.Http.ModelBinding.Binders.MutableObjectModelBinder.BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext) at System.Web.Http.Controllers.HttpActionContextExtensions.Bind(HttpActionContext actionContext, ModelBindingContext bindingContext, IEnumerable`1 binders) at System.Web.Http.ModelBinding.Binders.CompositeModelBinder.BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext) at System.Web.Http.ModelBinding.ModelBinderParameterBinding.ExecuteBindingAsync(ModelMetadataProvider metadataProvider, HttpActionContext actionContext, CancellationToken cancellationToken) at System.Web.Http.Controllers.HttpActionBinding.<ExecuteBindingAsyncCore>d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()
</StackTrace>
</Error>

Answer 1

只是一个快速更新。

我改变了一些东西，带来了一些新的结果。

首先我将AspNetJsonDeserializing 属性切换为HttpPost。

我也将AspNetJsonDeserializing参数ITestInstance instance属性切换为[FromBody]

现在显然，这迫使我通过 PostMan 调用它。

现在所有这些都删除了异常，但实例为空。在 ConcreteTestInstance 构造函数上没有遇到断点（我添加了另一个零参数构造函数以双向验证它）。

以下是所有变化。

[System.Web.Http.HttpPost]
public JsonResult<string> AspNetJsonDeserializing([FromBody] ITestInstance instance)
{
    ConcreteTestInstance myConcreteTestInstance = ((ConcreteTestInstance) instance);
    return Json($"Uri:{myConcreteTestInstance._instanceUri}");
}

这么短的故事，我还在寻找，为什么instance 为空

Answer 2

另一个更新。

我的代码现在可以与 HttpPost 一起使用。问题是 json 格式：FACEPALM:

在 PostMan 中我使用的格式是

{instance: {  
    "$type": "SimpleWebApi.Controllers.ConcreteTestInstance, SimpleWebApi", 
    "hostName": "google.com"  
}}

当我删除实例变量时，它纠正了问题。

另外，我测试过，ITestInstance 参数上的[FromBody] 属性是不相关的。

所以问题仍然存在，如何将这个功能作为 HttpGet 启用。

目前，当我将属性从 HttpPost 切换到 HttpGet 时，我开始收到第一篇文章中提到的异常。