Ok, two different questions, let me tackle each separately...
First, joko's question... AJAX isn't fundamentally complicated, it's in fact pretty simple in its most basic form. One suggest I would give is that if you aren't as comfortable in Javascript yet is to choose a good library because it will keep you away from some of the more complex details. Something like Prototype is a good choice. My own AjaxParts Taglib might be a good option since you are familiar with Java and JSP (
http://javawebparts.sourceforge.net ... hit the Javadocs link and look in the ajaxparts package). As for what to read, I'd suggest starting with a good beginning book on Javascript in general. One good choice might be "Beginning JavaScript with DOM Scripting and Ajax: From Novice to Professional" by Christian Heilmann (
http://apress.com/book/bookDisplay.html?bID=10134). My first book on AJAX might be good too, although it's billed as a medium-level book, so I'd be worried it might move a little fast at first.
Most importantly though, don't be scared of Javascript! There's really nothing to be scared about... your experience with Java means you already have a decent grasp of the basic syntax because they are pretty similar in that regard, and certainly there's a low barrier to entry (i.e., no compiler or anything, just pop open a text editor, drop some script in and load it up in your browser). As with all things, just spend a little time experimenting and it'll all come together pretty quickly.
Now, on to Purushotham... I'm not 100% sure I understand your question, but I'll try anyway... first, as for migrating Javascript to AJAX, rememebr that AJAX is just a way of using Javascript, so there's not really a migration per se. You may take a non-AJAX application and decide to throw some AJAX into it, I suppose you might consider that a migration. If that's what you mean, my book won't specifically show you how to do that. What it will do however is show you some examples of AJAX and how it can be used. However, AJAX is only one part of the Practical JavaScript Projects book... if you have a specific interest in AJAX, you may be better server by my first book, Practical Ajax Projects with Java Technologies. It's certainly more targeted.
As for embedding Java code in AJAX code, I'm not really sure what that means... certainly you can make an AJAX request to a server that uses a JSP, and thus Java, to render the response. And certainly a JSP could include AJAX code, if that's what you meant.
