在 vaadin 聊天对话框中输出 hello（Spring boot 和 spring scheduler + vaadin 14）

Question

I created a chat on the vaadine and spring boot. So I have a problem with the scheduler, I wanted to write a scheduler that displays "hello" every second, but how can I write so that it calls hello every second, only it was like this Example output -

hello 1 - (when 1 second has passed)
hello 2 - (after two seconds)
hello 3 - (after three seconds)
.
.
.
.
hello 45 - (after 45 seconds)
.
.
.
.
hello 100 - (after 100 seconds)

Image example

My code, How can I launch a sсheduler in a chat when I log in

public class MainView extends VerticalLayout {

    private final MessagesInfoManager messagesInfoManager;
    private final RestService restService;
    private String username;



     private int count=0;

    @Autowired
    public MainView(RestService restService) {
        this.messagesInfoManager = MessageConfigurator.getInstance().getChatMessagesInfoManager();
        addClassName("main-view");
        setSizeFull();
        setDefaultHorizontalComponentAlignment(Alignment.CENTER);

        H1 header = new H1("Vaadin Chat");
        header.getElement().getThemeList().add("dark");

        add(header);

        askUsername();
        this.restService = restService;
    }

    private void askUsername() {
        HorizontalLayout layout = new HorizontalLayout();
        TextField usernameField = new TextField();
        Button startButton = new Button("Start chat");

        layout.add(usernameField, startButton);

        startButton.addClickListener(click -> {
            username = usernameField.getValue();
            remove(layout);
            showChat(username);
        });

        add(layout);
    }

    private void showChat(String username) {
        MessageList messageList = new MessageList();

        List<Message> lasts = restService.getLast();
        for (Message message : lasts) {
            messageList.add(new Paragraph(message.getFrom() + ": " + message.getMessage()));
        }

        add(messageList, createInputLayout(username, messageList));
        expand(messageList);
    }

    private Component createInputLayout(String username, MessageList messageList) {
        HorizontalLayout layout = new HorizontalLayout();
        layout.setWidth("100%");

        TextField messageField = new TextField();
        messageField.addKeyDownListener(Key.ENTER, keyDownEvent -> sender(messageField, messageList));
        Button sendButton = new Button("Send");
        sendButton.addThemeVariants(ButtonVariant.LUMO_PRIMARY);

        layout.add(messageField, sendButton);
        layout.expand(messageField);

        messageField.addFocusListener(event -> {
            for (Message message : messagesInfoManager.getMessagesByUI(getUI())) {
                if (!message.getFrom().equals(username)) {
                    message.setUnread(false);
                    this.restService.updateMessage(message.getId(), message);
                }
            }
        });

        sendButton.addClickListener(click -> sender(messageField, messageList));
        messageField.focus();

        return layout;
    }

    private void sender(TextField textField, MessageList messageList) {
        Message message = new Message(username, textField.getValue());
        message = restService.saveMessage(message);
        messagesInfoManager.updateMessageUIInfo(new MessageInfo(messageList, message, this));
        textField.clear();
        textField.focus();
    }






@Scheduled (fixedDelay = 1000)
public void test() {
    count++; 
    System.out.println("Hello"+count);

}
}

In the compiler displays, now i need to chat

Answer 1

How you put up a scheduler in Java is not much related to Vaadin in itself. You can use a second thread that you run, or as you seem to have, a readymade tool for it. Looks like a Spring feature if I'm not mistaken.

After that, you update the Vaadin components to contain the new messages. You can for example make your messageList into a field and within test() add a new paragraph to it. Or use the backend service that you have to push messages in from there.

When you do update the UI from a secondary thread, remember that you might run into race conditions. For that reason, you should lock the user session for the time that you make UI changes .

Answer 2

@Scheduled(fixedDelay = 1000)
    public void test() {
        count++;
        System.out.println("Hello" + count);

        this.getUI().get().access(() -> {

            if (messageList != null) {
                messageList.add(new Paragraph("From me" + ": " + "Hello" + count));
            }

        });

    }
}