Question

我正在努力观察任务延续时发生的异常。方案是我在任务中进行api调用，并在ContinueWith上检查响应是否未经授权，如果是，那么我尝试更新auth令牌。如果更新auth令牌成功，那么我重试原始任务（api调用），如果失败则我抛出自定义AuthorizationFailedException以使任务失败。 ContinueWith有一个ObserveFailures扩展方法标记到它的末尾，它应该处理异常，但是我仍然得到异常未观察到的错误，这会导致应用程序崩溃。

代码很复杂，所以我试图在这里缩小代码：

拨打api电话：

protected virtual void ExecuteResults<TResponse> (TaskCompletionSource<QueryResponse<TResponse>> tcs, Func<Task<QueryResponse<TResponse>>> queryTask, CancellationToken token) {
            QueryResponse<TResponse> result = null;
            RenewTokensIfRequired (() => queryTask ())
                .ContinueWith (t => {
                    try {
                        result = t.Result;
                    } catch (Exception ex) {
                        ServiceLocator.Current.Resolve<ILoggingService> ().Log (CommonEnums.LogLevel.Info, "BaseDataService ExecuteAndCacheResults, ex: " + ex.ToString ());
                        if (!tcs.Task.IsCompleted)
                            tcs.SetException (ex);
                        return;
                    }
                    tcs.SetResult (result);
                }).ObserveFailures (tcs);
        }

如果api调用未经授权则处理更新auth令牌的包装器任务，如果更新auth令牌失败则抛出AuthenticationFailedException：

    public static Task<QueryResponse<TResult>> RenewTokensIfRequired<TResult> (Func<Task<QueryResponse<TResult>>> taskProvider, Func<AuthorizationContext, bool> shouldRetry = null) {
                if (shouldRetry == null)
                    shouldRetry = (context) => context.AuthorizationLevel != AuthEnums.AuthorizationLevel.None;
                return taskProvider ()
                    .ContinueWith (t => RenewTokenContinuation (t, taskProvider, shouldRetry, 1)).ObserveFailures ();
            }

    static QueryResponse<TResult> RenewTokenContinuation<TResult> (Task<QueryResponse<TResult>> task, Func<Task<QueryResponse<TResult>>> taskProvider, Func<AuthorizationContext, bool> shouldRetry, int attemptsRemaining) {
                var response = task.Result;
                if (response == null || response.HasAuthenticationFailure) {
                    if (attemptsRemaining > 0 && shouldRetry (AuthorizationContext.Current)) {
                        var context = AuthorizationContext.Current;
                        if (context.AuthorizationLevel == AuthEnums.AuthorizationLevel.Session) {
                            DataService.Auth.RenewSessionTokenAsync ().ObserveFailures ().Wait (10.Seconds ());
                            return taskProvider ()
                                .ContinueWith (retryTask => RenewTokenContinuation (retryTask, taskProvider, shouldRetry, --attemptsRemaining)).ObserveFailures ()
                                .Result;
                        }
                        if (context.AuthorizationLevel == AuthEnums.AuthorizationLevel.Device) {
                            DataService.Auth.RenewDeviceTokenAsync ().ObserveFailures ().Wait (10.Seconds ());
                            return taskProvider ()
                                .ContinueWith (retryTask => RenewTokenContinuation (retryTask, taskProvider, shouldRetry, --attemptsRemaining)).ObserveFailures ()
                                .Result;
                        }
                    }
                    ResetAuthentication ();
                }
                return response;
            }

private static void ResetAuthentication () {
            // If we make it this far, then we need to throw an AuthenticationException because we couldn't refresh a token
            AuthorizationContext.Current.SessionToken = null;
            AuthorizationContext.Current.DeviceToken = null;
            throw new AuthenticationFailedException ();
        }

然后，最后，这是ObserveFailures扩展方法，它应该处理异常，但似乎不是......

public static Task<T> ObserveFailures<T> (this Task<T> task, TaskCompletionSource<T> tcs = null) {
            task.ContinueWith (t => {
                TaskActions.LogException (t.Exception);
                if (tcs != null)
                    tcs.TrySetException (t.Exception);
            }, TaskContinuationOptions.OnlyOnFaulted);
            task.ContinueWith (t => {
                ServiceLocator.Current.Resolve<ILoggingService> ().Log (CommonEnums.LogLevel.Info, "The task was canceled");
                if (tcs != null)
                    tcs.TrySetCanceled ();
            }, TaskContinuationOptions.OnlyOnCanceled);
            return task;
        }

这是崩溃堆栈跟踪：

Xamarin引起的：android.runtime.JavaProxyThrowable： System.AggregateException：未观察到任务的异常通过等待任务或访问其Exception属性。如结果，终结器重新抛出了未观察到的异常线。 ---＆GT; System.AggregateException：发生一个或多个错误。 ---＆GT; RPR.Mobile.Shared.Exceptions.AuthenticationFailedException：Exception 类型'RPR.Mobile.Shared.Exceptions.AuthenticationFailedException' 被扔了。在 System.Threading.Tasks.TaskAuthorization.ResetAuthentication（） [0x00017] in /Users/justintoth/Documents/rpr-mobile/shared/Utility/Extensions/TaskExtensions.cs:310 在 System.Threading.Tasks.TaskAuthorization.RenewTokenContinuation [TResult] （System.Threading.Tasks.Task 1[TResult] task, System.Func 1 [TResult] taskProvider，System.Func 2[T,TResult] shouldRetry, System.Int32 attemptsRemaining) [0x0016b] in /Users/justintoth/Documents/rpr-mobile/shared/Utility/Extensions/TaskExtensions.cs:272 at System.Threading.Tasks.TaskAuthorization+<RenewTokenContinuation>c__AnonStorey2 1 [TResult]。＆lt;＆gt; m__0 （System.Threading.Tasks.Task 1[TResult] retryTask) [0x0001e] in /Users/justintoth/Documents/rpr-mobile/shared/Utility/Extensions/TaskExtensions.cs:261 at System.Threading.Tasks.ContinuationResultTaskFromResultTask 2 [TAntecedentResult，TResult] .InnerInvoke （）[0x00027] in /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/TaskContinuation.cs:207 在System.Threading.Tasks.Task.Execute（）[0x00016]中 /Users/builder/data/lanes/4468/f913a78a/source/mono/mcs/class/referencesource/mscorlib/system/threading/Tasks/Task.cs:2502

有什么想法吗？

通过等待任务或在继续时访问其异常属性，未观察到任务的异常

0 个答案: