【文章推荐】ASP.NET Core 中的正确的异常处理

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https://www.youtube.com/watch?v=-TGZypSinpw&ab_channel=NickChapsas

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在 RFC 7807 中，规定了可读的响应来避免更多的错误的内容规范。在 ASP.NET Core 的应用程序中可以优雅的方式完成这个要求。

1. 定义异常

对应不用的业务，可以定制不同的异常类型

[Serializable]
public class ProblemException : Exception
{
    public string Error { get;}
    public string Message { get; }
    public ProblemException(string error, string message) : base(message)
    {
        Error = error;
        Message = message;
    }
}

2. 定义 ExceptionHandler

public class ProblemExceptionHandler : IExceptionHandler
{

    private readonly IProblemDetailsService _problemDetailsService;

    public ProblemExceptionHandler(IProblemDetailsService problemDetailsService)
    {
        _problemDetailsService = problemDetailsService;
    }

    public async ValueTask<bool> TryHandleAsync(
        HttpContext httpContext,
        Exception exception,
        CancellationToken cancellationToken)
    {
        if (exception is not ProblemException problemException)
        {
            return true;
        }

        var problemDetails = new ProblemDetails();
        problemDetails.Status = StatusCodes.Status400BadRequest;
        problemDetails.Title = problemException.Error;
        problemDetails.Detail = problemException.Message;
        problemDetails.Type = "Bad Request";

        httpContext.Response.StatusCode = StatusCodes.Status400BadRequest;
        return await _problemDetailsService.TryWriteAsync(
            new ProblemDetailsContext()
            {
                HttpContext = httpContext,
                ProblemDetails = problemDetails,
            });
    }
}

3. 注册服务并且注册中间件

builder.Services.AddExceptionHandler<ProblemExceptionHandler>();
app.UseExceptionHandler();

4. 添加额外信息

builder.Services.AddProblemDetails(options =>
{
    options.CustomizeProblemDetails = context =>
    {
        context.ProblemDetails.Instance = $"{context.HttpContext.Request.Method} {context.HttpContext.Request.Path}";
        context.ProblemDetails.Extensions.TryAdd("requestId", context.HttpContext.TraceIdentifier);
        var activity = context.HttpContext.Features.Get<IHttpActivityFeature>()?.Activity;
        context.ProblemDetails.Extensions.TryAdd("traceId", activity?.Id);
    };
});

这样在任何需要错误的地方，只需要抛出 ProblemException 即可。