Spring Initializr Vaadin demo app, https://start.spring.io/

DemoApplication.java

package demo;

import com.vaadin.annotations.Theme;
import com.vaadin.server.VaadinRequest;
import com.vaadin.spring.annotation.SpringUI;
import com.vaadin.ui.Label;
import com.vaadin.ui.UI;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Service;

@SpringBootApplication
public class DemoApplication {

    // This is a runnable Spring Boot application
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    /* Business Service Facade.
     * Annotate your business services with @Service and they
     * will be autodetected by the framework.
     */
    @Service
    public static class MyService {
        
        public String sayHi() {
            return "Hello Spring Initializr!";
        }

    }

    /* Vaadin UI class.
     * Specify the theme and URI path for the 
     * web application.
     */
    @Theme("valo")
    @SpringUI(path = "")
    public static class VaadinUI extends UI {

        // You can easily autowire the services to you 
        // Vaadin applications
        @Autowired
        MyService myService;

        @Override
        protected void init(VaadinRequest request) {
            setContent(new Label(myService.sayHi()));
        }

    }
}

Yes, this just a helloworld. For full-featured Spring-Vaadin sample you should check out this one: https://github.com/mstahv/spring-data-vaadin-crud

There is also an another example with Spring Data, REST and server push: https://github.com/samie/spring-vaadin-demo