It is generally accepted that you submit a request to a
servlet for
java code handling, and use JSPs only for rendering the view (MVC)
I would actually recommend using a web framework which has supporting code that does the heavy lifting for things such as:
- mapping/converting parameters to beans
- validation of the bean and redisplay of the page(with errors) if necessary
- encourages you to use an MVC approach
Common examples are
Struts, Stripes,
JSF.
Personally I prefer Stripes right now, but there are a bunch of other out there I don't know about.