问为什么不在multiThreads应用程序中显示通知

EN

public MainView() {
    Button ipButton = getIpButton();

    setMargin(true);
    setHorizontalComponentAlignment(Alignment.START, ipButton);

    add(ipButton);
}

private Button getIpButton() {
        final UI ui = UI.getCurrent();
        final VaadinSession session = VaadinSession.getCurrent();

        Button ipButton = new Button("My IP");

        AtomicInteger orderIndex = new AtomicInteger();

        ipButton.addClickListener(_e -> {
            int orderThread = orderIndex.getAndIncrement();
            openBeginNotification(orderThread);

            executor.submit(() -> {
                try {
                    UI.setCurrent(ui);
                    VaadinSession.setCurrent(session);

                    long sleepTime = (long) (Math.random() * (10 - 5) + 5);
                    System.out.printf("%d: %ds\n", orderThread, sleepTime);

                    Thread.sleep(sleepTime * 1000);

                    IpDTO ip = restTemplate.getForObject("http://ip.jsontest.com/", IpDTO.class);
                    System.out.printf("%d: %s\n", orderThread, ip);

                    try {
                        VaadinSession.getCurrent().lock();
                        getFinishNotification(orderThread).open(); // here not show notification
                        VaadinSession.getCurrent().unlock();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            });
        });

    return ipButton;
}

private void openBeginNotification(int orderThread) {
    Notification notification;
    if (executor.getActiveCount() == MAX_THREADS) {
        // thread is in front
        notification = getWaitNotification(orderThread);
    }  else {
        // thread run
        notification = getRunNotification(orderThread);
    }
    notification.open();
}

private Notification getRunNotification(int orderThread) {
    return getNotification("Task " + orderThread + ": run", NotificationVariant.LUMO_PRIMARY);
}

private Notification getWaitNotification(int orderThread) {
    return getNotification("Task " + orderThread + ": wait", NotificationVariant.LUMO_CONTRAST);
}

private Notification getFinishNotification(int orderThread) {
    return getNotification("Task " + orderThread + ": finish", NotificationVariant.LUMO_SUCCESS);
}

private Notification getNotification(String notificationText, NotificationVariant variant) {
    Notification notification = new Notification(notificationText, 1000);
    notification.addThemeVariants(variant);

    return notification;
}