I'll jump in with the notorious "Do you really want to do that" answer.
It seems like your focus is on playing with Java and seeing what it can do. However, if you want to actually develop a web app, you should be aware that, although Java is used in web applications (and in serious ones), there are other technology options which might be more adequate.
Personally, I like (and use) Java for powerful, portable backend services on a server. I've never tried building websites with it, because it never seemed the most obvious ting to do. After growing tired of PHP (which I have been using for years), I lately fell in love with Django, a Python-based web framework.
The Ruby on Rails people have a number of very funny videos on youtube comparing different web technologies to RoR. Of course, these are obviously exaggerated and maybe slightly biased, but I'd say there's more than one grain of truth in each of them. The one about Java is here. ;-)
