vaadin-framework/test/servlet-containers/karaf/vaadin-karaf-bundle2/src/main/java/com/vaadin/test/osgi/myapplication/MyUI.java

package com.vaadin.test.osgi.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(event -> layout.addComponent(
                new Label("Thanks " + name.getValue() + ", it works!")));

        layout.addComponents(name, button);

        setContent(layout);
    }

    @Component(service = VaadinServlet.class)
    @WebServlet(urlPatterns = "/myapp2/*", name = "MyUIServlet", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
    public static class MyUIServlet extends VaadinServlet {
    }

}