Customizing Startup Page

Hi all,

i’m trying to load custom js in my ui.

Following this
article
i need to create a custom servlet. It’s possible use this on my UI??

I’m trying with VaadinService.getCurrent() but does’nt work. With VaadinSession.getCurrent().addBootstrapListener(new BootstrapListener() js are loaded only if i refresh the page. And if i refresh again i can see 2 js.