异常处理中间件和页面

Question

我是中间件概念的新手，目前正在努力寻找在我的 MVC Core 项目中处理异常的正确方法。

我想要发生的是捕获、记录异常，然后将用户发送到带有消息的友好错误页面。起初，我试图在中间件中管理所有这些，但意识到我可能做得不对。

所以如果我希望这个流程发生，我是否应该同时使用我的异常记录中间件和 app.UseExceptionHandler("/Error") 以便中间件将异常重新抛出到页面？如果是这样，我如何在错误页面中获取异常详细信息？我想先拦截的异常处理机制应该是Configure中的最后一个是否正确？

我发现的所有示例都严格处理 HTTP 状态码错误，例如 404；我正在寻找处理实际异常（及其子类）。这样，在我的视图页面中，我可以在适用的情况下抛出我自己的异常（例如，如果视图为必填字段提供了 null。）

Startup.cs sn-p:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, 
                      ILoggerFactory loggerFactory, LoanDbContext context) {
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    app.UseStatusCodePages();
    if (env.IsDevelopment() || env.IsEnvironment("qa")) {
        app.UseDeveloperExceptionPage();
        app.UseBrowserLink();
    } else {
        app.UseExceptionHandler("/Error");
    }
    app.UseMiddleware<MyExceptionHandler>(loggerFactory);
    // ... rest of Configure is irrelevant to this issue

MyExceptionHandler.cs

using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using System;
using System.Data.SqlClient;
using System.Threading.Tasks;

namespace MyCompany.MyProject.Helpers
{
    /// <summary>
    /// A custom Exception Handler Middleware which can be re-used in other projects.
    /// </summary>
    public sealed class MyExceptionHandler
    {
        private readonly RequestDelegate _next;
        private readonly ILogger _logger;

        public MyExceptionHandler(RequestDelegate next, ILoggerFactory loggerFactory) {
            _next = next;
            _logger = loggerFactory.CreateLogger<MyExceptionHandler>();
        }

        public async Task Invoke(HttpContext context) {
            try {
                await _next(context);
            } catch (Exception ex) {
                HandleException(ex);
            }
        }

        // I realize this function looks pointless, but it will have more meat to it eventually.
        public void HandleException(Exception ex) {
            if (ex is ArgumentException argEx) {
                _logger.LogError(0, argEx, argEx.Message);
            } else if (ex is InvalidOperationException ioEx) {
                _logger.LogError(0, ioEx, "An Invalid Operation Exception occurred. This is usually caused by a database call that expects "
                    + "one result, but receives none or more than one.");
            } else if (ex is SqlException sqlEx) {
                _logger.LogError(0, sqlEx, $"A SQL database exception occurred. Error Number {sqlEx.Number}");
            } else if (ex is NullReferenceException nullEx) {
                _logger.LogError(0, nullEx, $"A Null Reference Exception occurred. Source: {nullEx.Source}.");
            } else if (ex is DbUpdateConcurrencyException dbEx) {
                _logger.LogError(0, dbEx, "A database error occurred while trying to update your item. This is usually due to someone else modifying the item since you loaded it.");
            } else {
                _logger.LogError(0, ex, "An unhandled exception has occurred.")
            }
        }
    }
}

Answer 1

我是否应该同时使用我的异常记录中间件和app.UseExceptionHandler("/Error")，以便中间件重新向页面抛出异常？

是的。

仅使用示例的 sn-p。

public async Task Invoke(HttpContext context) {
    try {
        await _next(context);
    } catch (Exception ex) {
        HandleException(ex);
         // re -throw the original exception
         // after logging the information
        throw;
    }
}

上面将在记录后重新抛出原始错误，以便管道中的其他处理程序将捕获它并进行开箱即用的处理。

来源Error Handling in ASP.NET Core

如何在错误页面获取异常详情？

使用IExceptionHandlerPathFeature获取异常和路径

public IActionResult Error()
{
    // Get the details of the exception that occurred
    var exceptionFeature = HttpContext.Features.Get<IExceptionHandlerPathFeature>();

    if (exceptionFeature != null)
    {
        // Get which route the exception occurred at
        string routeWhereExceptionOccurred = exceptionFeature.Path;

        // Get the exception that occurred
        Exception exceptionThatOccurred = exceptionFeature.Error;

        // TODO: Do something with the exception
        // Log it with Serilog?
        // Send an e-mail, text, fax, or carrier pidgeon?  Maybe all of the above?
        // Whatever you do, be careful to catch any exceptions, otherwise you'll end up with a blank page and throwing a 500
    }

    return View();
}

来源Adding Global Error Handling and Logging in ASP.NET Core with IExceptionHandlerPathFeature

在上面的示例中，他们提到在视图中进行日志记录，但您已经在自定义处理程序中完成了。

在呈现错误视图时要特别注意这个小注释。

无论你做什么，都要小心捕捉任何异常，否则你会得到一个空白页并抛出 500

通过插入管道，您可以避免重新发明框架已经提供的开箱即用的功能，并且还可以管理横切关注点。