以不同于非 API 异常的方式处理 API 异常。将代码移动到外部 class 库时出错

Question

我正在尝试对我的网络 API 控制器和我的非网络 API 控制器进行不同的异常处理。换句话说，我想要这个声明

app.UseExceptionHandler("/Home/Error");

，这是在 Microsoft.AspNetCore.Diagnostics、

中找到的扩展

适用于除以 /api 开头的所有 URL。我已经编写了一些代码来执行此操作，并且在将其包含在 Web 项目中时可以正常工作。但是，如果我将此代码移至另一个程序集，则会出现错误。

我已经使用 ASP.NET Core 5 编写了一些代码来演示我的问题。

Program.cs


using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;

namespace ExceptionHandling
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

Startup.cs


using ExceptionHandlingUtils;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;

namespace ExceptionHandling
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        public void Configure(IApplicationBuilder app)
        {

            app.UseaNonApiExceptionHandler("/Home/Error");  // this is my custom middleware, for implementation see below
            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
}

下面是调用它的自定义中间件和扩展方法。 ExceptionHandlerExtensions 几乎是从 here. And the code for ExceptionHandlerMiddleware.cs is here

复制而来的

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;

namespace ExceptionHandling.Middleware
{
    public static class ExceptionHandlerExtensions
    {
        public static IApplicationBuilder UseaNonApiExceptionHandler(this IApplicationBuilder app, string errorHandlingPath)
        {
            return app.UseaNonApiExceptionHandler(new ExceptionHandlerOptions
            {
                ExceptionHandlingPath = new PathString(errorHandlingPath)
            });
        }

        public static IApplicationBuilder UseaNonApiExceptionHandler(this IApplicationBuilder app, ExceptionHandlerOptions options)
        {
            return app.UseMiddleware<NonApiExceptionHandler>(Options.Create(options));
        }
    }
}

NonApiExceptionHandler.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System.Diagnostics;
using System.Threading.Tasks;

namespace ExceptionHandling
{
        public class NonApiExceptionHandler
    {
        private readonly ExceptionHandlerMiddleware _exceptionHandlerMiddleware;
        private readonly RequestDelegate _next;

        public NonApiExceptionHandler(
            RequestDelegate next,
            ILoggerFactory loggerFactory,
            IOptions<ExceptionHandlerOptions> options,
            DiagnosticListener diagnosticListener)

        {
            _next = next;
            _exceptionHandlerMiddleware = new ExceptionHandlerMiddleware(next, loggerFactory, options, diagnosticListener);

        }

        public async Task Invoke(HttpContext context)
        {
            if (context.Request.Path.StartsWithSegments("/api"))
            {
                await _next(context);
                return;
            }

            await _exceptionHandlerMiddleware.Invoke(context);
        }
    }
}

这是我的控制器

using Microsoft.AspNetCore.Mvc;
using System;

namespace ExceptionHandling.Controllers
{
    public class HomeController: Controller
    {
        public IActionResult Index()
        {
            throw new Exception("an error");
        }

        public IActionResult Error()
        {
            return Content("an error has occured");
        }
    }
}

这是我的网站 API 控制器

using Microsoft.AspNetCore.Mvc;
using System;

namespace ExceptionHandling.Controllers.api
{
    [Route("api/[controller]")]
    [ApiController]
    public class MyApiController: ControllerBase
    {

        public IActionResult Get()
        {
            throw new Exception("an error");
        }
    }
}

以上代码按预期工作。 IE。如果您导航到 / 然后抛出异常，您将被重定向到 /home/error 并显示消息。如果您导航到 /api/myapi，则会抛出异常，但不会将您重定向到 /home/error。

因为这是我的许多网站都需要的功能，所以我试图将这段代码放入另一个程序集中。换句话说，我将我的启动文件更改为这个

using ExceptionHandlingUtils;  //note the namespace change, this is the same code but in a different 
                                //assembly
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;

namespace ExceptionHandling
{
    public class Startup
    {

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        public void Configure(IApplicationBuilder app)
        {

            app.UseaNonApiExceptionHandler("/Home/Error");          

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
}

并将 2 个自定义中间件文件移动到一个 class 库，目标为 .NET 5，命名空间为 ExceptionHandlingUtils。该库导入了 nuget 包 Microsoft.AspNetCore.Diagnostics。当我运行相同的代码但从单独的程序集调用我的自定义中间件时，我收到以下错误

An error occurred while starting the application.
MissingMethodException: Method not found: 'Void Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware..ctor(Microsoft.AspNetCore.Http.RequestDelegate, Microsoft.Extensions.Logging.ILoggerFactory, Microsoft.Extensions.Options.IOptions`1<Microsoft.AspNetCore.Builder.ExceptionHandlerOptions>, System.Diagnostics.DiagnosticSource)'.
ExceptionHandlingUtils.NonApiExceptionHandler..ctor(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<ExceptionHandlerOptions> options, DiagnosticListener diagnosticListener)

MissingMethodException: Method not found: 'Void Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware..ctor(Microsoft.AspNetCore.Http.RequestDelegate, Microsoft.Extensions.Logging.ILoggerFactory, Microsoft.Extensions.Options.IOptions`1<Microsoft.AspNetCore.Builder.ExceptionHandlerOptions>, System.Diagnostics.DiagnosticSource)'.
ExceptionHandlingUtils.NonApiExceptionHandler..ctor(RequestDelegate next, ILoggerFactory loggerFactory, IOptions<ExceptionHandlerOptions> options, DiagnosticListener diagnosticListener)
System.RuntimeMethodHandle.InvokeMethod(object target, object[] arguments, Signature sig, bool constructor, bool wrapExceptions)
System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, object[] parameters, CultureInfo culture)
Microsoft.Extensions.Internal.ActivatorUtilities+ConstructorMatcher.CreateInstance(IServiceProvider provider)
Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, object[] parameters)
Microsoft.AspNetCore.Builder.UseMiddlewareExtensions+<>c__DisplayClass5_0.<UseMiddleware>b__0(RequestDelegate next)
Microsoft.AspNetCore.Builder.ApplicationBuilder.Build()
Microsoft.AspNetCore.Hosting.GenericWebHostService.StartAsync(CancellationToken cancellationToken)
Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken)
Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run(IHost host)
ExceptionHandling.Program.Main(string[] args) in Program.cs
+
            CreateHostBuilder(args).Build().Run();

我想知道如何修复这个错误。或者还有另一种方法可以从 Microsoft.AspNetCore.Diagnostics 获取 ExceptionHandlerMiddleware 以忽略我的网络 API urls.

Answer 1

我建议使用 UseWhen，而不是创建自定义中间件 class、NonApiExceptionHandler，它会创建 ExceptionHandlerMiddleware 的实例：[=24] =]

Conditionally creates a branch in the request pipeline that is rejoined to the main pipeline.

这是一个使用 UseWhen 的最小示例：

app.UseWhen(
   context => !context.Request.Path.StartsWithSegments("/api"),
   nonApiApp => nonApiApp.UseExceptionHandler("/Home/Error"));

传递给UseWhen的第一个参数表示管道将被分支的条件。在这种情况下，UseExceptionHandler 将影响不以 /api 开头的请求。

您可以将其包装在扩展方法中，就像您在问题中所做的那样，以便它可以重复使用。这是一个简单的例子：

public static class ExceptionHandlerExtensions
{
    public static IApplicationBuilder UseaNonApiExceptionHandler(
        this IApplicationBuilder app, string errorHandlingPath)
    {
        return app.UseWhen(
            context => !context.Request.Path.StartsWithSegments("/api"),
            nonApiApp => nonApiApp.UseExceptionHandler(errorHandlingPath));
    }

    // ...
}

有关 UseWhen 的更多详细信息，包括它与 MapWhen 的比较，请参阅 Branch the middleware pipeline。

以不同于非 API 异常的方式处理 API 异常。将代码移动到外部 class 库时出错

Handle API exceptions differently to non API exceptions. Errors when moving code to an external class library

c#

middleware

asp.net-core-mvc

asp.net-core

asp.net-core-webapi