Application_Error和异常过滤器

Question

所以我最近在ExceptionFilter上构建了它，它可以处理除Api错误之外的所有错误。异常筛选器如下所示：

public class ExceptionAttribute : IExceptionFilter
{
    /// <summary>
    /// Handles any exception
    /// </summary>
    /// <param name="filterContext">The current context</param>
    public void OnException(ExceptionContext filterContext)
    {
        // If our exception has been handled, exit the function
        if (filterContext.ExceptionHandled)
            return;
        // If our exception is not an ApiException
        if (!(filterContext.Exception is ApiException))
        {
            // Set our base status code
            var statusCode = (int)HttpStatusCode.InternalServerError;
            // If our exception is an http exception
            if (filterContext.Exception is HttpException)
            {
                // Cast our exception as an HttpException
                var exception = (HttpException)filterContext.Exception;
                // Get our real status code
                statusCode = exception.GetHttpCode();
            }
            // Set our context result
            var result = CreateActionResult(filterContext, statusCode);
            // Set our handled property to true
            filterContext.ExceptionHandled = true;
        }
    }
    /// <summary>
    /// Creats an action result from the status code
    /// </summary>
    /// <param name="filterContext">The current context</param>
    /// <param name="statusCode">The status code of the error</param>
    /// <returns></returns>
    protected virtual ActionResult CreateActionResult(ExceptionContext filterContext, int statusCode)
    {
        // Create our context
        var context = new ControllerContext(filterContext.RequestContext, filterContext.Controller);
        var statusCodeName = ((HttpStatusCode)statusCode).ToString();
        // Create our route
        var controller = (string)filterContext.RouteData.Values["controller"];
        var action = (string)filterContext.RouteData.Values["action"];
        var model = new HandleErrorInfo(filterContext.Exception, controller, action);
        // Create our result
        var view = SelectFirstView(context, string.Format("~/Views/Error/{0}.cshtml", statusCodeName), "~/Views/Error/Index.cshtml", statusCodeName);
        var result = new ViewResult { ViewName = view, ViewData = new ViewDataDictionary<HandleErrorInfo>(model) };
        // Return our result
        return result;
    }
    /// <summary>
    /// Gets the first view name that matches the supplied names
    /// </summary>
    /// <param name="context">The current context</param>
    /// <param name="viewNames">A list of view names</param>
    /// <returns></returns>
    protected string SelectFirstView(ControllerContext context, params string[] viewNames)
    {
        return viewNames.First(view => ViewExists(context, view));
    }
    /// <summary>
    /// Checks to see if a view exists
    /// </summary>
    /// <param name="context">The current context</param>
    /// <param name="name">The name of the view to check</param>
    /// <returns></returns>
    protected bool ViewExists(ControllerContext context, string name)
    {
        var result = ViewEngines.Engines.FindView(context, name, null);
        return result.View != null;
    }
}

如您所见，如果错误不是ApiException，那么我将用户路由到错误控制器。ApiException 只是我从 MVC 中进行 API 调用时发生的错误。当这些错误发生时，我想将错误作为JSON返回给客户端，以便JavaScript可以处理它。

我以为不处理错误会这样做，但它会产生一个服务器错误(尽管其中有 JSON 错误(，如下所示：

"/"应用程序中的服务器错误。

{"消息"："验证移动验证失败：\r项目已发送，无法移动"}

说明：执行当前 Web 请求期间发生未经处理的异常。请查看堆栈跟踪，了解有关错误及其在代码中起源位置的详细信息。

异常详细信息： SapphirePlus.Web.ApiException： {"message"："validateMove 验证失败：\r项目已发送，无法移动"}

源错误：

第 181 行：如果(响应。StatusCode ！= HttpStatusCode.OK(

第 182 行：抛出新的 ApiException(结果(;

所以我的问题是，我能否获得Application_Error方法来获取 ApiException的错误并将错误作为 JSON 返回？

Answer 1

所以我的问题是，我能得到Application_Error方法吗？ 错误是 ApiExceptions 并将错误作为 JSON 返回？

答案是肯定的：

protected void Application_Error()
{
    var apiException = Server.GetLastError() as ApiException;
    if (apiException != null)
    {
        Response.Clear();
        Server.ClearError();
        Response.StatusCode = 400;
        Context.Response.ContentType = "application/json";
        Context.Response.Write("YOUR JSON HERE");
    }
}

Answer 2

最后我根本不需要使用 Global.asax，我能够在我的 ExceptionAttribute 类中像这样处理它：

public class ExceptionAttribute : IExceptionFilter
{
    /// <summary>
    /// Handles any exception
    /// </summary>
    /// <param name="filterContext">The current context</param>
    public void OnException(ExceptionContext filterContext)
    {
        // If our exception has been handled, exit the function
        if (filterContext.ExceptionHandled)
            return;
        // Set our base status code
        var statusCode = (int)HttpStatusCode.BadRequest;
        // If our exception is an http exception
        if (filterContext.Exception is HttpException)
        {
            // Cast our exception as an HttpException
            var exception = (HttpException)filterContext.Exception;
            // Get our real status code
            statusCode = exception.GetHttpCode();
        }
        // Set our context result
        var result = CreateActionResult(filterContext, statusCode);
        // Set our handled property to true
        filterContext.Result = result;
        filterContext.ExceptionHandled = true;
    }
    /// <summary>
    /// Creats an action result from the status code
    /// </summary>
    /// <param name="filterContext">The current context</param>
    /// <param name="statusCode">The status code of the error</param>
    /// <returns></returns>
    protected virtual ActionResult CreateActionResult(ExceptionContext filterContext, int statusCode)
    {
        // Create our context
        var context = new ControllerContext(filterContext.RequestContext, filterContext.Controller);
        var statusCodeName = ((HttpStatusCode)statusCode).ToString();
        // Create our route
        var controller = (string)filterContext.RouteData.Values["controller"];
        var action = (string)filterContext.RouteData.Values["action"];
        var model = new HandleErrorInfo(filterContext.Exception, controller, action);
        // Create our result
        var view = SelectFirstView(context, string.Format("~/Views/Error/{0}.cshtml", statusCodeName), "~/Views/Error/Index.cshtml", statusCodeName);
        var result = new ViewResult { ViewName = view, ViewData = new ViewDataDictionary<IError>(this.Factorize(model)) };
        // Return our result
        return result;
    }
    /// <summary>
    /// Factorizes the HandleErrorInfo
    /// </summary>
    /// <param name="error"></param>
    /// <returns></returns>
    protected virtual IError Factorize(HandleErrorInfo error)
    {
        // Get the error
        var model = new Error
        {
            Message = "There was an unhandled exception."
        };
        // If we have an error
        if (error != null)
        {
            // Get our exception
            var exception = error.Exception;
            // If we are dealing with an ApiException
            if (exception is ApiException || exception is HttpException)
            {
                // Get our JSON
                var json = JObject.Parse(exception.Message);
                var message = json["exceptionMessage"] != null ? json["exceptionMessage"] : json["message"];
                // If we have a message
                if (message != null)
                {
                    // Update our model message
                    model.Message = message.ToString();
                }
            }
            else
            {
                // Update our message
                model.Message = exception.Message;
            }
        }
        // Return our response
        return model;
    }
    /// <summary>
    /// Gets the first view name that matches the supplied names
    /// </summary>
    /// <param name="context">The current context</param>
    /// <param name="viewNames">A list of view names</param>
    /// <returns></returns>
    protected string SelectFirstView(ControllerContext context, params string[] viewNames)
    {
        return viewNames.First(view => ViewExists(context, view));
    }
    /// <summary>
    /// Checks to see if a view exists
    /// </summary>
    /// <param name="context">The current context</param>
    /// <param name="name">The name of the view to check</param>
    /// <returns></returns>
    protected bool ViewExists(ControllerContext context, string name)
    {
        var result = ViewEngines.Engines.FindView(context, name, null);
        return result.View != null;
    }
}

这处理了任何 Mvc 错误，对于我的 API 调用，我这样做了：

    /// <summary>
    /// Used to handle the api response
    /// </summary>
    /// <param name="response">The HttpResponseMessage</param>
    /// <returns>Returns a string</returns>
    private async Task<string> HandleResponse(HttpResponseMessage response)
    {
        // Read our response content
        var result = await response.Content.ReadAsStringAsync();
        // If there was an error, throw an HttpException
        if (response.StatusCode != HttpStatusCode.OK)
            throw new ApiException(result);
        // Return our result if there are no errors
        return result;
    }

这允许我捕获 ApiError 并以不同于任何其他异常的方式处理响应。