class AccessDeniedSubscriber

class AccessDeniedSubscriber implements EventSubscriberInterface {
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $account;
    
    /**
     * Constructs a new redirect subscriber.
     *
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The current user.
     */
    public function __construct(AccountInterface $account) {
        $this->account = $account;
    }
    
    /**
     * Redirects users when access is denied.
     *
     * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
     *   The event to process.
     */
    public function onException(ExceptionEvent $event) {
        $exception = $event->getThrowable();
        if ($exception instanceof AccessDeniedHttpException) {
            $route_name = RouteMatch::createFromRequest($event->getRequest())
                ->getRouteName();
            $redirect_url = NULL;
            if ($this->account
                ->isAuthenticated()) {
                switch ($route_name) {
                    case 'user.login':
                        // Redirect an authenticated user to the profile page.
                        $redirect_url = Url::fromRoute('entity.user.canonical', [
                            'user' => $this->account
                                ->id(),
                        ], [
                            'absolute' => TRUE,
                        ]);
                        break;
                    case 'user.register':
                        // Redirect an authenticated user to the profile form.
                        $redirect_url = Url::fromRoute('entity.user.edit_form', [
                            'user' => $this->account
                                ->id(),
                        ], [
                            'absolute' => TRUE,
                        ]);
                        break;
                }
            }
            elseif ($route_name === 'user.page') {
                $redirect_url = Url::fromRoute('user.login', [], [
                    'absolute' => TRUE,
                ]);
            }
            elseif (in_array($route_name, [
                'user.logout',
                'user.logout.confirm',
            ], TRUE)) {
                $redirect_url = Url::fromRoute('<front>', [], [
                    'absolute' => TRUE,
                ]);
            }
            if ($redirect_url) {
                $event->setResponse(new RedirectResponse($redirect_url->toString()));
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        // Use a higher priority than
        // \Drupal\Core\EventSubscriber\ExceptionLoggingSubscriber, because there's
        // no need to log the exception if we can redirect.
        $events[KernelEvents::EXCEPTION][] = [
            'onException',
            75,
        ];
        return $events;
    }

}