MyUI.java

package com.example.myapplication;

import javax.servlet.annotation.WebServlet;

import org.osgi.service.component.annotations.Component;

import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Button;
import com.vaadin.ui.Label;
import com.vaadin.ui.TextField;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

public class MyUI extends UI {

	@Override
	protected void init(VaadinRequest vaadinRequest) {
		final VerticalLayout layout = new VerticalLayout();

		final TextField name = new TextField();
		name.setCaption("Type your name here:");

		Button button = new Button("Click Me");
		button.addClickListener(e -> {
			layout.addComponent(new Label("Thanks " + name.getValue() + ", it works!"));
		});

		layout.addComponents(name, button);

		setContent(layout);
	}

	@Component(service = VaadinServlet.class)
	@WebServlet(urlPatterns = "/myapp/*", name = "MyUIServlet", asyncSupported = true)
	@VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
	public static class MyUIServlet extends VaadinServlet {
	}
}