This chapter provides a brief overview of AJAX that introduces the technologies and concepts behind it. Because there are so many approaches to implementing AJAX techniques in Web applications, a comprehensive review of AJAX is outside the scope of this book. Instead this chapter will highlight a very basic approach for using AJAX by integrating AJAX into the Mini HR application. Although quite simple, this example provides insight into the foundation that all AJAX-based frameworks use, such as the popular DWR (http://getahead.ltd.uk/dwr/) and Dojo (http://dojotoolkit.org/) frameworks.
As a point of interest, there are two Struts AJAX extensions available on the http://struts.sf.net/ site, AjaxTags and AjaxChat, which are useful for developing Struts applications that leverage AJAX.