also recommended
For an introduction to Ajax i would recommend the "Head Rush Ajax" book. Part of the HeadFirst series.
Publisher: O’Reilly
Everybody loves Ajax. Javaists, Rubyists, Pythonistas; even Microsofties get to play with Ajax in the form of Atlas. Book publishers love Ajax too, judging by the stack of new titles coming hot off the presses. O'Reilly has added to the pile with a new title in their long-running "Hacks" series. The aim of the series is to …
Ajax book covers the Ruby on Rails with Ajax, but does not cover some other Ajax topics such:
1. AjaxTags- are used in a JSP page to send an Ajax request.
http://ajaxtags.sourceforge.net/
2. Ajax4JSF-integrates Ajax with JSF.
https://ajax4jsf.dev.java.net/nonav/ajax/ajax-jsf/