package com.example; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import com.vaadin.server.VaadinRequest; import com.vaadin.spring.annotation.SpringUI; import com.vaadin.ui.Button; import com.vaadin.ui.Notification; import com.vaadin.ui.UI; @SpringBootApplication public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } } @SpringUI class MyUI extends UI { public static final String NOTIFICATION_TEXT = "Thank you for clicking."; @Override protected void init(VaadinRequest request) { setContent(new Button("Click Me!", e -> Notification.show(NOTIFICATION_TEXT))); } }