VaadinUI Keeps Loading when I add ComboBox

Hi All,

I am facing strange issue. My vaading page is keeps loading when I add combobox component in to it. I was using Vaadin legacy now I have upgraded to Vaadin7. Could some please help me to come out of this issue :-(

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.ComboBox;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

/**
 * This UI is the application entry point. A UI may either represent a browser window 
 * (or tab) or some part of a 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("mytheme")
public class MyUI extends UI {

    @Override
    protected void init(VaadinRequest vaadinRequest) {
        final VerticalLayout layout = new VerticalLayout();      
        ComboBox select = new ComboBox("Select");
        
        select.addItem("1");
        select.addItem("2");
        
        layout.addComponents(select);
        layout.setMargin(true);
        layout.setSpacing(true);
        
        setContent(layout);
    }

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

Issue resolved its due to wrong dependancy configuration in Gradle:

Bellow the right one
    compile "com.vaadin:vaadin-bom:7.7.7"
    compile "javax.servlet:javax.servlet-api:3.0.1"
    compile "com.vaadin:vaadin-server:7.7.7"
    compile "com.vaadin:vaadin-push:7.7.7"
    compile "com.vaadin:vaadin-client-compiled:7.7.7"
    compile "com.vaadin:vaadin-themes:7.7.7"