Vaadin lets you build secure, UX-first PWAs entirely in Java.
Free ebook & tutorial.
I didn't quite understand sorry about that. Can you explain in more detail. Do you want to integrate some Vaadin app into an HTML page or do you want the HTML page to live inside a Vaadin app somehow?
If you have carefully evaluated the use case and are sure, that the core Vaadin components and add-ons from Directory don't suffice.