[In a rush to get this posted I forgot to mention the URL for the project... it's the same as my ASP.NET stuff (check the releases you'll find it). The URL is http://www.codeplex.com/dtajax/]
In case you missed it (I think everyone either didn't notice it or didn't care... I'm not really sure which), I released my JSP Tag framework for using MS Ajax' Client Library with JSP. Actually It's a combined release. It has some of my stuff, some of the MS Ajax library stuff, and some of the Ajax Toolkit stuff (as well as a single control I like to test with which was originally written by Nikhil Kothari).
So Why Java?
Honestly, because I needed it. I have learned the MS Ajax platform at a really low level and I really didn't want to trade off that knowledge to have to start over again. So... I built my own JSP tag framework (well, framework is a stretch).
How does it work?
Take a look at the Sample pages and you'll start to get an idea. Basically you need a ScriptManagerJ tag on your page (there's also an early version of this called ScriptManagerB). ScriptManagerJ takes some attributes for where the scripts are and it also has some attributes where you tell it what you want to enable. Under the covers it goes out and figures which scripts are actually needed for the functionality you want. It's not complicated... just a simple set of ifs determine what files are need to take care of all the dependencies.
Then its a matter of using one of the other tags to wire up the functionality. They work just like the ASP.NET extenders, so for instance the ACTktAlwaysVisible tag is the equivalent of the Ajax Control Toolkit's (ACTkt) AlwaysVisible extender. You simple provide the targetControlID and any other pertinent info and the JavaScript code needed to activate the underlying behavior is wired up for you.
Right now all the easier stuff has been wired up. Stuff like the CascadingDropDown will require a little more effort as there are underlying Server-Side components at work (but never fear, I have a plan already).
What's coming?
I don't know... how about an UpdatePanel? I've got some good ideas on how to build one. If I can get it working and get it integrated with the MS Ajax client library then that will open up a whole new class of controls.
With what I am learning/have learned about the Client Library, I may (and I stress may) be able to make all this somewhat available in ASP.NET 1.1 or how about 1.0? ASP would also be doable... You see this is just the first step... there are more on the way.