UI file

package com.library.librarytest;

import com.ejt.vaadin.loginform.DefaultVerticalLoginForm;
import com.ejt.vaadin.loginform.LoginForm.LoginEvent;
import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.UI;

/**
 * This UI is the application entry point. A UI may either represent a browser window
 * (or tab) or some part of an HTML page where a Vaadin application is embedded.
 * <p>
 * The UI is initialized using {@link #init(VaadinRequest)}. This method is intended to be
 * overridden to add component to the user interface and initialize non-component functionality.
 */
@Theme("valo")
@SuppressWarnings("serial")
public class MyUI extends UI {

    @Override
    protected void init(VaadinRequest vaadinRequest) {

       DefaultVerticalLoginForm loginForm = new DefaultVerticalLoginForm();
loginForm.addLoginListener((LoginEvent event) -> {
    System.err.println(
            "Logged in with user name " + event.getUserName() +
                    " and password of length " + event.getPassword().length());
       });


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