我正在编辑一个使用MVC3的旧项目。 它有一个 Global.asax 文件，可以处理如下错误：
protected void Application_Error(object sender, EventArgs e)
{
var currentController = " ";
var currentAction = " ";
var currentRouteData = RouteTable.Routes.GetRouteData(new HttpContextWrapper(Context));
if (currentRouteData != null)
{
if (currentRouteData.Values["controller"] != null && !String.IsNullOrEmpty(currentRouteData.Values["controller"].ToString()))
currentController = currentRouteData.Values["controller"].ToString();
if (currentRouteData.Values["action"] != null && !String.IsNullOrEmpty(currentRouteData.Values["action"].ToString()))
currentAction = currentRouteData.Values["action"].ToString();
}
var ex = Server.GetLastError();
var controller = new ErrorController();
var routeData = new RouteData();
var action = "Index";
var code = (ex is HttpException) ? (ex as HttpException).GetHttpCode() : 500;
switch (code)
{
case 400:
action = "BadRequest";
break;
case 401:
action = "Unauthorized";
break;
case 403:
action = "Forbidden";
break;
case 404:
action = "NotFound";
break;
case 500:
action = "InternalServerError";
break;
default:
action = "Index";
break;
}
Server.ClearError();
Response.Clear();
Response.StatusCode = code;
Response.TrySkipIisCustomErrors = true;
routeData.Values["controller"] = "Error";
routeData.Values["action"] = action;
controller.ViewData.Model = new HandleErrorInfo(ex, currentController, currentAction);
((IController)controller).Execute(new RequestContext(new HttpContextWrapper(Context), routeData));
}
当我的MVC项目中存在错误时，这可以正常工作。 还有一个基类可以调用外部API，如下所示：
/// <summary>
/// Used to make a Get request to a specified url
/// </summary>
/// <param name="url">The target url</param>
/// <returns>Returns a string</returns>
public async Task<string> MakeApiCall(string url)
{
return await MakeApiCall(url, HttpMethod.GET, null);
}
/// <summary>
/// Used to make a Post request to a specified url
/// </summary>
/// <param name="url">The target url</param>
/// <param name="method">The Http method</param>
/// <param name="data">The object to send to the api</param>
/// <returns>Returns a string</returns>
public async Task<string> MakeApiCall(string url, HttpMethod method, object data)
{
// Create our local variables
var client = new HttpClient();
var user = Session["AccessToken"];
var authenticating = user == null;
// If we are not authenticating, set our auth token
if (!authenticating)
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", Session["AccessToken"].ToString());
// Check to see what HTTP method is being used
switch (method)
{
case HttpMethod.POST:
// If we are POSTing, then perform a post request
return await PostRequest(client, url, data, authenticating);
default:
// If we are GETing, then perform a get request
return await GetRequest(client, url);
}
}
#region Helper methods
/// <summary>
/// Posts data to a specifed url
/// </summary>
/// <param name="client">The HttpClient used to make the api call</param>
/// <param name="url">The target url</param>
/// <param name="data">The object to send to the api</param>
/// <param name="authenticating">Used to set the content type when authenticating</param>
/// <returns>Returns a string</returns>
private async Task<string> PostRequest(HttpClient client, string url, object data, bool authenticating)
{
// If the data is a string, then do a normal post, otherwise post as json
var response = (data is string) ? await client.PostAsync(this.apiUrl + url, new StringContent(data.ToString())) : await client.PostAsJsonAsync(this.apiUrl + url, data);
// If we are authenticating, set the content type header
if (authenticating == true)
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
// Handle our response
return await HandleResponse(response);
}
/// <summary>
/// Gets data from a specifed url
/// </summary>
/// <param name="client">The HttpClient used to make the api call</param>
/// <param name="url">The target url</param>
/// <returns>Returns a string</returns>
private async Task<string> GetRequest(HttpClient client, string url)
{
// Perform the get request
var response = await client.GetAsync(this.apiUrl + url);
// Handle our response
return await HandleResponse(response);
}
/// <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 HttpException((int)response.StatusCode, result);
// Return our result if there are no errors
return result;
}
#endregion
我采用这种方法的问题是 HandleResponse 方法。 当进行API调用时，如果调用失败，它就会落在这一行：
// If there was an error, throw an HttpException
if (response.StatusCode != HttpStatusCode.OK)
throw new HttpException((int)response.StatusCode, result);
反过来由 Global.asax 中的 Application_Error 方法捕获。这个问题是，因为这是一个API调用，控制器无法重定向到 ErrorController ......
所以我的问题是：
如果您有任何疑问，请询问。我试图确保帖子不仅仅是一面文字。
更新1
所以，我尝试使用AttributeFilter来帮助解决这个问题。 我使用了2个用户建议的2种方法。首先，我创建了一个自定义例外，如下所示：
/// <summary>
/// Custom Api Exception
/// </summary>
public class ApiException : Exception
{
/// <summary>
/// Default constructor
/// </summary>
public ApiException()
{
}
/// <summary>
/// Constructor with message
/// </summary>
/// <param name="message">The error message as a string</param>
public ApiException(string message)
: base(message)
{
}
/// <summary>
/// Constructor with message and inner exception
/// </summary>
/// <param name="message">The error message as a string</param>
/// <param name="inner">The inner exception</param>
public ApiException(string message, Exception inner)
: base(message, inner)
{
}
}
然后我在基本控制器中更新了我的 HandleResponse 方法，如下所示：
/// <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;
}
然后我创建了一个过滤器，我添加到 FilterConfig ，看起来像这样：
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;
}
}
最后我从 Global.asax 中的 Application_Error 方法中删除了逻辑，希望这可行。但事实并非如此。当ApiException时，我仍然会返回一个文档。
任何人都可以帮助我吗？
答案 0 :(得分：1)
我可以以某种方式忽略Global.asax错误处理并返回JSON，以便我的JavaScript可以决定如何处理错误
由于Global.asax是ASP.NET管道的一部分，因此没有本机方法可以忽略它。你可以尝试一些黑客攻击，但如果你使用MVC和WebApi框架解决问题而不是依赖过时的ASP.NET行为会更好。
有更好的方法吗？
答案 1 :(得分：0)
如果你想用最少量的代码完成你想要做的事情，那么你可以做的不是抛出HttpException而是可以以字符串的形式返回一个代表你的异常的序列化JSON（从那以后）你的方法返回字符串）如下：
if (response.StatusCode != HttpStatusCode.OK)
JsonConvert.SerializeObject("{ StatusCode : " + response.StatusCode.ToString() + "}");
显然，这是一个黑客攻击，不推荐练习，但它不会设置Application_Error，您也可以将JSON回复到您的客户端代码。
更好的选择是重构代码以返回HttpResponseMessage或使用过滤器属性等。