asp.net-web-api – OWIN中间件中的全局异常处理

我正在ASP.NET Web API 2.1项目中创建一个统一的错误处理/报告，该项目构建在OWIN中间件(IIS HOST使用Owin.Host.SystemWeb)之上。
目前，我使用了一个自定义的异常记录器，它继承自System.Web.Http.ExceptionHandling.ExceptionLogger，并使用NLog将所有异常作为下面的代码记录：

public class NLogExceptionLogger : ExceptionLogger
{

    private static readonly Logger Nlog = LogManager.GetCurrentClassLogger();
    public override void Log(ExceptionLoggerContext context)
    {
       //Log using NLog
    } 
}

我想将所有API异常的响应体更改为友好的统一响应，它将使用System.Web.Http.ExceptionHandling.ExceptionHandler隐藏所有异常详细信息作为以下代码：

public class ContentNegotiatedExceptionHandler : ExceptionHandler
{
    public override void Handle(ExceptionHandlerContext context)
    {
        var errorDataModel = new ErrorDataModel
        {
            Message = "Internal server error occurred,error has been reported!",Details = context.Exception.Message,ErrorReference = context.Exception.Data["ErrorReference"] != null ? context.Exception.Data["ErrorReference"].ToString() : string.Empty,DateTime = DateTime.UtcNow
        };

        var response = context.Request.CreateResponse(HttpStatusCode.InternalServerError,errorDataModel);
        context.Result = new ResponseMessageResult(response);
    }
}

当异常发生时，这将返回以下客户端的响应：

{
  "Message": "Internal server error occurred,"Details": "Ooops!","ErrorReference": "56627a45d23732d2","DateTime": "2015-12-27T09:42:40.2982314Z"
}

现在，如果在Api Controller请求管道中发生任何异常，这一切都会很好。

但是在我的情况下，我正在使用中间件Microsoft.Owin.Security.OAuth来生成承载令牌，而这个中间件并不知道有关Web API异常处理的任何内容，所以例如如果异常已经被抛出在ValidateClientAuthentication方法中NLogExceptionLogger没有ContentNegotiatedExceptionHandler将知道有关此异常的任何操作，也不会尝试处理它，AuthorizationServerProvider中使用的示例代码如下所示：

public class AuthorizationServerProvider : OAuthAuthorizationServerProvider
{
    public override Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
    {
        //Expcetion occurred here
        int x = int.Parse("");

        context.Validated();
        return Task.FromResult<object>(null);
    }

    public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
    {
        if (context.UserName != context.Password)
        {
            context.SetError("invalid_credentials","The user name or password is incorrect.");
            return;
        }

        var identity = new ClaimsIdentity(context.Options.AuthenticationType);

        identity.AddClaim(new Claim(ClaimTypes.Name,context.UserName));

        context.Validated(identity);
    }
}

所以我会感谢执行下面2个问题的任何指导：

1 – 创建一个全局异常处理程序，仅处理由OWIN中间商产生的异常？我跟着this answer，创建了一个异常处理目的的中间件，并将其注册为第一个，并且我能够执行源自“OAuthAuthorizationServerProvider”的日志异常，但是我不知道这是否是最佳的方法。

2 – 现在当我在上一步中实现日志记录时，我真的不知道如何更改异常的响应，因为在“OAuthAuthorizationServerProvider”中发生异常时，我需要向客户端返回一个标准的JSON模型。有一个相关的answer here我试图依赖，但它没有工作。

这是我的启动类和我为异常捕获/记录创建的自定义GlobalExceptionMiddleware。失踪的和平正在为任何异常返回统一的JSON响应。任何想法将不胜感激。

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var httpConfig = new HttpConfiguration();

        httpConfig.MapHttpAttributeRoutes();

        httpConfig.Services.Replace(typeof(IExceptionHandler),new ContentNegotiatedExceptionHandler());

        httpConfig.Services.Add(typeof(IExceptionLogger),new NLogExceptionLogger());

        OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
        {
            AllowInsecureHttp = true,TokenEndpointPath = new PathString("/token"),AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),Provider = new AuthorizationServerProvider()
        };

        app.Use<GlobalExceptionMiddleware>();

        app.USEOAuthAuthorizationServer(OAuthServerOptions);
        app.USEOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

        app.UseWebApi(httpConfig);
    }
}

public class GlobalExceptionMiddleware : OwinMiddleware
{
    public GlobalExceptionMiddleware(OwinMiddleware next)
        : base(next)
    { }

    public override async Task Invoke(IOwinContext context)
    {
        try
        {
            await Next.Invoke(context);
        }
        catch (Exception ex)
        {
            NLogLogger.LogError(ex,context);
        }
    }
}

解决方法

您需要将这个中间件注册为Startup类中的第一个，如下所示：

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var httpConfig = new HttpConfiguration();

        httpConfig.MapHttpAttributeRoutes();

        httpConfig.Services.Replace(typeof(IExceptionHandler),Provider = new AuthorizationServerProvider()
        };

        //Should be the first handler to handle any exception happening in OWIN middlewares
        app.USEOwinExceptionHandler();

        // Token Generation
        app.USEOAuthAuthorizationServer(OAuthServerOptions);

        app.USEOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

        app.UseWebApi(httpConfig);
    }
}

而在OwinExceptionHandlerMiddleware中使用的代码如下所示：

using AppFunc = Func<IDictionary<string,object>,Task>;

public class OwinExceptionHandlerMiddleware
{
    private readonly AppFunc _next;

    public OwinExceptionHandlerMiddleware(AppFunc next)
    {
        if (next == null)
        {
            throw new ArgumentNullException("next");
        }

        _next = next;
    }

    public async Task Invoke(IDictionary<string,object> environment)
    {
        try
        {
            await _next(environment);
        }
        catch (Exception ex)
        {
            try
            {

                var owinContext = new OwinContext(environment);

                NLogLogger.LogError(ex,owinContext);

                HandleException(ex,owinContext);

                return;
            }
            catch (Exception)
            {
                // If there's a Exception while generating the error page,re-throw the original exception.
            }
            throw;
        }
    }
    private void HandleException(Exception ex,IOwinContext context)
    {
        var request = context.Request;

        //Build a model to represet the error for the client
        var errorDataModel = NLogLogger.BuildErrorDataModel(ex);

        context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
        context.Response.ReasonPhrase = "Internal Server Error";
        context.Response.ContentType = "application/json";
        context.Response.Write(JsonConvert.SerializeObject(errorDataModel));

    }

}

public static class OwinExceptionHandlerMiddlewareAppBuilderExtensions
{
    public static void USEOwinExceptionHandler(this IAppBuilder app)
    {
        app.Use<OwinExceptionHandlerMiddleware>();
    }
}

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