在Blazor中使用JsonPatchDocument发生意外错误

如何解决在Blazor中使用JsonPatchDocument发生意外错误

我正在使用Blazor WebAssembly（WASM）客户端通过.NET Core REST API执行更新。为此，我通过HTTP PATCH请求发送了JsonPatchDocument<T>，其中T是我应用程序的数据传输对象（DTO）之一。

它不起作用。我在Blazor应用程序中返回了500个内部服务器错误状态代码。我在Postman中了解了更多细节，但不足以让我理解问题。

这是我的Blazor WASM应用程序中的调用代码：

@code
{
[Parameter]
public int BookId { get; set; } = 101;

private async Task HandleClickAsync()
{
    string newTitle = "How to make JsonPatchDocument work with Blazor - Second Edition";

    var patchDocument = new JsonPatchDocument<Book>()
        .Replace(c => c.Title,newTitle);

    var json = JsonSerializer.Serialize(patchDocument);
    var content = new StringContent(json,Encoding.UTF8,"application/json-patch+json");
    var response = await HttpClient.PatchAsync($"https://localhost:44367/api/books/{BookId}",content);


    if (response.IsSuccessStatusCode)
    {
        // Handle success
    }
    else if (response.StatusCode == HttpStatusCode.NotFound)
    {
        // Handle not found
    }
    else
    {
        // Handle unexpected failures
    }
}
}

这是我的控制器方法：

[ApiController]
[Route("api/[controller]")]
public class BooksController : ControllerBase
{
    [HttpPatch("{id:int}")]
    public async Task<ActionResult> PatchAsync(
        int id,[FromBody] JsonPatchDocument<Book> patch)
    {
        // We're just going to fake an asynchronous database call and return a 200 status code to the client
        await Task.FromResult(true);
        return Ok();
    }
}

这是我的DTO：

public class Book
{
    public int Id { get; set; }

    public string Title { get; set; }
}

我发送的补丁文档序列化为JSON时，如下所示：

{"Operations":[{"value":"How to make JsonPatchDocument work with Blazor - Second Edition","OperationType":2,"path":"/Title","op":"replace","from":null}],"ContractResolver":{}}

我在邮递员中看到的错误详细信息是：

System.NotSupportedException: Deserialization of interface types is not supported. Type 'Newtonsoft.Json.Serialization.IContractResolver'
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException_DeserializeCreateObjectDelegateIsNull(Type invalidType)
   at System.Text.Json.JsonSerializer.HandleStartObject(JsonSerializerOptions options,ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadCore(JsonSerializerOptions options,Utf8JsonReader& reader,ReadStack& readStack)
   at System.Text.Json.JsonSerializer.ReadCore(JsonReaderState& readerState,Boolean isFinalBlock,ReadOnlySpan`1 buffer,JsonSerializerOptions options,ReadStack& readStack)
   at System.Text.Json.JsonSerializer.ReadAsync[TValue](Stream utf8Json,Type returnType,CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context,Encoding encoding)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context,Encoding encoding)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Binders.BodyModelBinder.BindModelAsync(ModelBindingContext bindingContext)
   at Microsoft.AspNetCore.Mvc.ModelBinding.ParameterBinder.BindModelAsync(ActionContext actionContext,IModelBinder modelBinder,IValueProvider valueProvider,ParameterDescriptor parameter,ModelMetadata metadata,Object value)
   at Microsoft.AspNetCore.Mvc.Controllers.ControllerBinderDelegateProvider.<>c__DisplayClass0_0.<<CreateBinderDelegate>g__Bind|0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker,Task lastTask,State next,Scope scope,Object state,Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker,Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next,Scope& scope,Object& state,Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker,Task task,IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint,Task requestTask,ILogger logger)
   at Microsoft.AspNetCore.Builder.Extensions.MapWhenMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Builder.Extensions.MapMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

HEADERS
=======
Accept: */*
Accept-Encoding: gzip,deflate,br
Cache-Control: no-cache
Connection: keep-alive
Content-Length: 175
Content-Type: application/json
Host: localhost:44367
User-Agent: PostmanRuntime/7.26.3
Postman-Token: b4444f41-b80f-4ef5-92d5-2416d68d471e

我的项目中没有一个直接依赖Newtonsoft。我不知道我引用的Microsoft库是否依赖于Newtonsoft。该错误表明也许他们这样做。

该行为可以在GitHub上的这个小存储库中观察到： https://github.com/BenjaminCharlton/JsonPatchDocumentWithBlazor

请问有人知道为什么它不起作用和/或会解决什么问题吗？

谢谢

解决方法

我设法解决了这一难题，Pavel和Enet的输入都很有用，谢谢。

对于其他遇到相同问题的人，这是您需要解决的问题：

1. 截至目前（2020年末），将.NET Core从Newtonsoft.Json移至System.Text.Json的努力还没有完成。软件包Microsoft.AspNetCore.JsonPatch仍然取决于Newtonsoft.Json。

2. .NET Core开发团队意识到GitHub在报告此问题方面存在很多问题。但是他们都没有采取任何行动而被关闭。显然，将Microsoft.AspNetCore.JsonPatch切换到System.Text.Json涉及很多工作。

3. 要将Newtonsoft用于JsonPatch，而不能将其他there is a nice little hack described here用于Web API /服务器项目的Startup类中。特别注意在GetJsonPatchInputFormatter

   内部调用的Startup.ConfigureServices辅助方法的使用

4. 但是，单独使用它可能无法解决Blazor WASM /客户端项目将收到的50X和40X HTTP错误，因为如果使用JsonPatch序列化System.Text.Json，它将添加一个空的ContractResolver对象到JSON字符串的末尾（看起来像,"ContractResolver":{} ），它在服务器端中断。由于某种原因，该请求与您所执行的任何控制器路由都不匹配。

5. 要解决此问题，您还必须在Blazor客户端上使用Newtonsoft.Json。您不必将其用于所有内容；您只需要使用它来序列化所有JsonPatch。与Newtonsoft.Json相比，System.Text.Json的代码行多了几行，但是我做了一个扩展方法，因此不会在各处重复。扩展方法如下：

    public static class HttpClientExtensions
    {
        public static async Task<HttpResponseMessage> PatchAsync<T>(this HttpClient client,string requestUri,JsonPatchDocument<T> patchDocument)
        where T : class
    {
        var writer = new StringWriter();
        var serializer = new JsonSerializer();
        serializer.Serialize(writer,patchDocument);
        var json = writer.ToString();
   
        var content = new StringContent(json,Encoding.UTF8,"application/json-patch+json");
        return await client.PatchAsync(requestUri,content);
    }
   

   }

就是这样。此解决方法对我有用，我希望对您也有用。