Can a person build a professional desktop-style interactive ‘single-page’ web app without learning the alphabet soup of HTTP, HTML, CSS, JavaScript, DOM, AJAX, XML, JSON, Comet, WebSocket, and Push?

Yes! Vaadin is the open-source framework for building a web app user interface using only Java on the backend. You layout a form with buttons, fields, labels, and other widgets either programmatically or by using a visual drag-and-drop form editor. Then let Vaadin automagically render that app in the user’s browser using web-standard technologies. Vaadin generates and delivers the HTML, CSS, and JavaScript on your behalf.

You get rich, flexible, and fast user-interface instantly deployed to most any browser client-side while enjoying the speed, security, reliability, and vast libraries of Java on the server-side. 

Over a decade-old, Vaadin is mature and proven, used by over 150,000 programmers world-wide, and is rapidly growing in popularity.  See online demos here and here. See Wikipedia article.