Java

AjaxTags

Web site: http://ajaxtags.sourceforge.net/

License: Apache 2.0

AjaxTags is a set of JSP tags designed to make it easy to add AJAX to Java JSP sites. Each tag implements a specific widget. These tags include support for an auto-complete text box, pop-up balloons, multistep select boxes, tabbed panels, and area displays. Tags are also offered for making HTML content replacement. Prototype, scriptaculous, and OverLIB are used on the client side. XML is used for communication between the client and the server.

Direct Web Remoting (DWR)

Web site: http://getahead.ltd.uk/dwr/overview/dwr

License: Apache

DWR offers an easy way to export Java classes and make them accessible from JavaScript applications. DWR does this by generating JavaScript proxy classes that match the Java ones. This operation works much like HTML_AJAX's RPC mechanism (described in Chapter 9). The Java classes can be configured using XML or annotations. A number of utility JavaScript functions are also included to make standard DOM-manipulation tasks easier.

Google Web Toolkit

Web site: http://code.google.com/webtoolkit/

License: Mix of Apache 2.0 and free-to-use components

Google Web Toolkit allows Java developers to make AJAX applications without writing JavaScript. The heart of the toolkit is a special compiler that translates the Java application into JavaScript and HTML. The toolkit includes a user-interface library with a large number of widgets, including standard HTML form elements, menu bars, trees, tables, dialog boxes, and various panels for managing the layout of the application. A custom event model based on a listener pattern is provided, as is an API for managing style sheets. RPC support is provided using code generation to hide the hard work, and data serialization is provided for most basic Java types. The toolkit also includes back-button management and debugging tools.

ZK

Web site: http://zk1.sourceforge.net/

License: GPL and commercial

ZK is a component- and widget-based AJAX library. It allows you to build AJAX applications without writing JavaScript. Its widgets are geared toward building complete applications; thus, it would be hard from a style-and-usability perspective to integrate it into existing Web sites. (This isn't unique to ZK; many widget-based toolkits have a similar problem.) ZK has a large set of widgets, from standard HTML form elements to trees and modal dialog boxes. ZK applications are developed using a custom ZUML markup language (which is similar to Mozilla's XUL) with embedded Java.