java Spring调度器示例（Spring boot和Vaadin 14项目）

Question

我创建了一个用于交流的聊天。对于我使用vaadin的界面，我想测试聊天，当聊天打开时，它需要每1秒启动一次（hello 1，hello 2，hello 3……）我写了一个时间表，但它怎么可能是正确的呢？我好像写错了

MainView

    public class MainView extends VerticalLayout {

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

    @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() {
    System.out.println("Hello");
    }
    }

Mainview中的调度程序

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

我的例子

@Scheduled (fixedDelay = 1000)
public void test() {
    count++; 

    System.out.println("Hello"+count);


}

Answer 1

启用调度

只需将@EnableScheduling注释添加到主应用程序类或任何配置类，即可启用调度

安排任务

安排任务就像用@Scheduled annotation注释方法一样简单

在下面的示例中，execute（）方法计划每秒运行一次。在本例中，execute（）方法应该调用所需的服务方法lke getAllMessages（）

@EnableScheduling
public class MainView extends ... {

    // Existing Code

    @Autowired
    private MessageServiceImpl messageService;

    @Scheduled(fixedRate = 1000)
    public void execute() {
        messageService.getAllMessages();
    }

}

日程安排类型

1. 固定费率调度

   execute() method can be scheduled to run with a fixed interval using fixedRate parameter.

   @Scheduled(fixedRate = 2000)
   

2. 固定延迟调度

   execute() method can be scheduled to run with a fixed delay between the completion of the last invocation and the start of the next, using fixedDelay parameter.

   @Scheduled(fixedDelay = 2000)
   

3. 具有初始延迟和固定速率/固定延迟的调度

   initialDelay parameter with fixedRate and fixedDelay to delay the first execution.

   @Scheduled(fixedRate = 2000, initialDelay = 5000)
   

   @Scheduled(fixedDelay= 2000, initialDelay = 5000)
   

4. 使用cron进行调度

   execute() method can be scheduled to run based on cron expression using cron parameter.

   @Scheduled(cron = "0 * * * * *")