我使用ASP。NET核心为我的新的REST API项目后使用常规的ASP。NET Web API很多年了。我看不出在ASP中有什么处理异常的好方法。NET核心Web API。我尝试实现一个异常处理过滤器/属性:

public class ErrorHandlingFilter : ExceptionFilterAttribute
{
    public override void OnException(ExceptionContext context)
    {
        HandleExceptionAsync(context);
        context.ExceptionHandled = true;
    }

    private static void HandleExceptionAsync(ExceptionContext context)
    {
        var exception = context.Exception;

        if (exception is MyNotFoundException)
            SetExceptionResult(context, exception, HttpStatusCode.NotFound);
        else if (exception is MyUnauthorizedException)
            SetExceptionResult(context, exception, HttpStatusCode.Unauthorized);
        else if (exception is MyException)
            SetExceptionResult(context, exception, HttpStatusCode.BadRequest);
        else
            SetExceptionResult(context, exception, HttpStatusCode.InternalServerError);
    }

    private static void SetExceptionResult(
        ExceptionContext context, 
        Exception exception, 
        HttpStatusCode code)
    {
        context.Result = new JsonResult(new ApiResponse(exception))
        {
            StatusCode = (int)code
        };
    }
}

这是我的启动过滤器注册:

services.AddMvc(options =>
{
    options.Filters.Add(new AuthorizationFilter());
    options.Filters.Add(new ErrorHandlingFilter());
});

我遇到的问题是,当我的AuthorizationFilter发生异常时,它没有被ErrorHandlingFilter处理。我希望它能像以前的ASP一样被捕获。NET Web API。

那么我如何捕捉所有应用程序异常以及任何异常从动作过滤器?


当前回答

在任何特定方法上处理异常的简单方法是:

using Microsoft.AspNetCore.Http;
...

public ActionResult MyAPIMethod()
{
    try
    {
       var myObject = ... something;

       return Json(myObject);
    }
    catch (Exception ex)
    {
        Log.Error($"Error: {ex.Message}");
        return StatusCode(StatusCodes.Status500InternalServerError);
    }         
}

其他回答

首先,感谢Andrei,因为我的解决方案是基于他的例子。

我把我的样本包括在内,因为它是一个更完整的样本,可能会为读者节省一些时间。

Andrei的方法的局限性是不能处理日志记录,捕获潜在有用的请求变量和内容协商(无论客户端请求什么——XML /纯文本等等,它总是返回JSON)。

我的方法是使用一个ObjectResult,它允许我们使用烘焙到MVC中的功能。

这段代码还可以防止缓存响应。

错误响应已被修饰成可以由XML序列化器序列化的方式。

public class ExceptionHandlerMiddleware
{
    private readonly RequestDelegate next;
    private readonly IActionResultExecutor<ObjectResult> executor;
    private readonly ILogger logger;
    private static readonly ActionDescriptor EmptyActionDescriptor = new ActionDescriptor();

    public ExceptionHandlerMiddleware(RequestDelegate next, IActionResultExecutor<ObjectResult> executor, ILoggerFactory loggerFactory)
    {
        this.next = next;
        this.executor = executor;
        logger = loggerFactory.CreateLogger<ExceptionHandlerMiddleware>();
    }

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await next(context);
        }
        catch (Exception ex)
        {
            logger.LogError(ex, $"An unhandled exception has occurred while executing the request. Url: {context.Request.GetDisplayUrl()}. Request Data: " + GetRequestData(context));

            if (context.Response.HasStarted)
            {
                throw;
            }

            var routeData = context.GetRouteData() ?? new RouteData();

            ClearCacheHeaders(context.Response);

            var actionContext = new ActionContext(context, routeData, EmptyActionDescriptor);

            var result = new ObjectResult(new ErrorResponse("Error processing request. Server error."))
            {
                StatusCode = (int) HttpStatusCode.InternalServerError,
            };

            await executor.ExecuteAsync(actionContext, result);
        }
    }

    private static string GetRequestData(HttpContext context)
    {
        var sb = new StringBuilder();

        if (context.Request.HasFormContentType && context.Request.Form.Any())
        {
            sb.Append("Form variables:");
            foreach (var x in context.Request.Form)
            {
                sb.AppendFormat("Key={0}, Value={1}<br/>", x.Key, x.Value);
            }
        }

        sb.AppendLine("Method: " + context.Request.Method);

        return sb.ToString();
    }

    private static void ClearCacheHeaders(HttpResponse response)
    {
        response.Headers[HeaderNames.CacheControl] = "no-cache";
        response.Headers[HeaderNames.Pragma] = "no-cache";
        response.Headers[HeaderNames.Expires] = "-1";
        response.Headers.Remove(HeaderNames.ETag);
    }

    [DataContract(Name= "ErrorResponse")]
    public class ErrorResponse
    {
        [DataMember(Name = "Message")]
        public string Message { get; set; }

        public ErrorResponse(string message)
        {
            Message = message;
        }
    }
}

下面是微软的官方指南,涵盖了所有版本的。net的WebAPI和MVC案例。

对于Web API,它建议重定向到专用控制器端点以返回ProblemDetails。因为这可能会导致OpenAPI规范中不打算直接调用的端点的潜在暴露,我建议一个更简单的解决方案:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    ...

    app.UseExceptionHandler(a => a.Run(async context =>
    {
        var error = context.Features.Get<IExceptionHandlerFeature>().Error;
        var problem = new ProblemDetails { Title = "Critical Error"};
        if (error != null)
        {
            if (env.IsDevelopment())
            {
                problem.Title = error.Message;
                problem.Detail = error.StackTrace;
            }
            else
                problem.Detail = error.Message;
        }
        await context.Response.WriteAsJsonAsync(problem);
    }));
    ...
}

在这种情况下,我们利用一个标准的中间件来返回定制的详细信息(用于开发模式的堆栈跟踪),并避免创建“内部”端点。

注:官方指南依赖于。net v3之前的IExceptionHandlerPathFeature,此后(到目前为止v5)依赖于IExceptionHandlerFeature。

p.s.如果你从域层抛出异常,将它们转换为4xx代码,我建议使用khellang的ProblemDetailsMiddleware或返回DomainResult,可以稍后转换为IActionResult或IResult。后一个选项可以帮助您实现相同的结果,而不需要异常的开销。

在任何特定方法上处理异常的简单方法是:

using Microsoft.AspNetCore.Http;
...

public ActionResult MyAPIMethod()
{
    try
    {
       var myObject = ... something;

       return Json(myObject);
    }
    catch (Exception ex)
    {
        Log.Error($"Error: {ex.Message}");
        return StatusCode(StatusCodes.Status500InternalServerError);
    }         
}

这个被广泛接受的答案对我帮助很大,但是我想在中间件中传递HttpStatusCode,以便在运行时管理错误状态代码。

根据这个链接,我有一些想法去做同样的事情。所以我把安德烈的答案和这个合并了。所以我的最终代码如下:

1. 基类

public class ErrorDetails
{
    public int StatusCode { get; set; }
    public string Message { get; set; }

    public override string ToString()
    {
        return JsonConvert.SerializeObject(this);
    }
}

2. 自定义异常类类型

public class HttpStatusCodeException : Exception
{
    public HttpStatusCode StatusCode { get; set; }
    public string ContentType { get; set; } = @"text/plain";

    public HttpStatusCodeException(HttpStatusCode statusCode)
    {
        this.StatusCode = statusCode;
    }

    public HttpStatusCodeException(HttpStatusCode statusCode, string message) 
        : base(message)
    {
        this.StatusCode = statusCode;
    }

    public HttpStatusCodeException(HttpStatusCode statusCode, Exception inner) 
        : this(statusCode, inner.ToString()) { }

    public HttpStatusCodeException(HttpStatusCode statusCode, JObject errorObject) 
        : this(statusCode, errorObject.ToString())
    {
        this.ContentType = @"application/json";
    }

}

3.自定义异常中间件

public class CustomExceptionMiddleware
{
    private readonly RequestDelegate next;

    public CustomExceptionMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context /* other dependencies */)
    {
        try
        {
            await next(context);
        }
        catch (HttpStatusCodeException ex)
        {
            await HandleExceptionAsync(context, ex);
        }
        catch (Exception exceptionObj)
        {
            await HandleExceptionAsync(context, exceptionObj);
        }
    }

    private Task HandleExceptionAsync(HttpContext context, HttpStatusCodeException exception)
    {
        string result = null;
        context.Response.ContentType = "application/json";
        if (exception is HttpStatusCodeException)
        {
            result = new ErrorDetails() 
            {
                Message = exception.Message,
                StatusCode = (int)exception.StatusCode 
            }.ToString();
            context.Response.StatusCode = (int)exception.StatusCode;
        }
        else
        {
            result = new ErrorDetails() 
            { 
                Message = "Runtime Error",
                StatusCode = (int)HttpStatusCode.BadRequest
            }.ToString();
            context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
        }
        return context.Response.WriteAsync(result);
    }

    private Task HandleExceptionAsync(HttpContext context, Exception exception)
    {
        string result = new ErrorDetails() 
        { 
            Message = exception.Message,
            StatusCode = (int)HttpStatusCode.InternalServerError 
        }.ToString();
        context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
        return context.Response.WriteAsync(result);
    }
}

4. 扩展方法

public static void ConfigureCustomExceptionMiddleware(this IApplicationBuilder app)
{
    app.UseMiddleware<CustomExceptionMiddleware>();
}

5. 在startup.cs中配置Method

app.ConfigureCustomExceptionMiddleware();
app.UseMvc();

现在我在帐户控制器中的登录方法:

try
{
    IRepository<UserMaster> obj 
        = new Repository<UserMaster>(_objHeaderCapture, Constants.Tables.UserMaster);
    var result = obj.Get()
        .AsQueryable()
        .Where(sb => sb.EmailId.ToLower() == objData.UserName.ToLower() 
            && sb.Password == objData.Password.ToEncrypt() 
            && sb.Status == (int)StatusType.Active)
        .FirstOrDefault();
    if (result != null)//User Found
        return result;
    else // Not Found
        throw new HttpStatusCodeException(HttpStatusCode.NotFound,
            "Please check username or password");
}
catch (Exception ex)
{
    throw ex;
}

上面你可以看到,如果我没有找到用户,然后引发HttpStatusCodeException,其中我已经传递了HttpStatusCode。中间件中的NotFound状态和自定义消息

catch (HttpStatusCodeException ex)

block将被调用,它将把控制传递给

private Task HandleExceptionAsync HttpStatusCodeException异常)方法

但如果我得到运行时错误之前?为此,我使用了try catch块抛出异常,并将在catch (exception exceptionObj)块中捕获,并将控制传递给

任务HandleExceptionAsync(HttpContext上下文,异常异常)

方法。为了保持一致性,我使用了一个ErrorDetails类。

要配置每种异常类型的异常处理行为,您可以使用NuGet包中的中间件:

Community.AspNetCore.ExceptionHandling.NewtonsoftJson ASP。NET Core 2.0 ASP. aspnetcore . exceptionhandling . mvcNET Core 2.1+。

代码示例:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddExceptionHandlingPolicies(options =>
    {
        options.For<InitializationException>().Rethrow();

        options.For<SomeTransientException>().Retry(ro => ro.MaxRetryCount = 2).NextPolicy();

        options.For<SomeBadRequestException>()
        .Response(e => 400)
            .Headers((h, e) => h["X-MyCustomHeader"] = e.Message)
            .WithBody((req,sw, exception) =>
                {
                    byte[] array = Encoding.UTF8.GetBytes(exception.ToString());
                    return sw.WriteAsync(array, 0, array.Length);
                })
        .NextPolicy();

        // Ensure that all exception types are handled by adding handler for generic exception at the end.
        options.For<Exception>()
        .Log(lo =>
            {
                lo.EventIdFactory = (c, e) => new EventId(123, "UnhandlerException");
                lo.Category = (context, exception) => "MyCategory";
            })
        .Response(null, ResponseAlreadyStartedBehaviour.GoToNextHandler)
            .ClearCacheHeaders()
            .WithObjectResult((r, e) => new { msg = e.Message, path = r.Path })
        .Handled();
    });
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseExceptionHandlingPolicies();
    app.UseMvc();
}