The book's focus is on AJAX as a technology and I'm confident that it can introduce you to the world of AJAX showing you some real world examples.
You can take a look at the free downloadable chapters from the book to make a first impression about what you can expect from this book
http://ajaxphp.packtpub.com/ The programming language chosen for this book is PHP but you can easily migrate the examples to
Java(Servlets/JSP).
After you understand AJAX, the language used for the server side is completely your choice. I recommand PHP as it is very easy to start AJAX with PHP.
Bogdan