code: public function onException (ExceptionEvent $event)
  	{
  		$exception = $event->exception;
  		$craft = \Craft::$app;
  
  		if (!($exception instanceof HttpException) || $exception->statusCode !== 404)
  			return;
  
  		$path = $craft->request->getFullPath();
  		$query = $craft->request->getQueryStringWithoutPath();
  
  		if ($query)
  			$path .= '?' . $query;
  
  		if ($redirect = $this->findRedirectByPath($path))
  		{
  			$event->handled = true;
  			$craft->response->redirect($redirect['to'], $redirect['type'])
  			                ->send();
  			$craft->end();
  		}
  	}
docs: Handles 404 exceptions
  
  @param ExceptionEvent $event
  
  @return void
  @throws \yii\base\Exception
  @throws \yii\base\ExitException