Echo2 is a reinvention of the Echo Web Framework built around an Ajax (Asynchronous JavaScript and XML) rendering engine. Distributed under the Mozilla Public License, Echo2 aims at providing a component-oriented/event-driven toolkit for developing web applications that approach the capabilities of rich clients.

For a sample demonstration application written using Echo2, please visit:
http://demo.nextapp.com/InteractiveTest/ia

Echo2 uses the array of Ajax technologies in the interest of providing a more rich-client-like user experience. All client/server interaction is accomplished over an XMLHttpRequest wire. An entire Echo application runs from within a single web page--with nary a reload nor full page update. User input is sent to the server by POSTing XML documents over XMLHttpRequests. The server reciprocates with XML messages containing synchronization instructions which are then processed by pluggable client-side JavaScript modules. The net result is a markedly more fluid and "desktop-like" user experience and a dramatic performance improvement when compared to traditional web application technologies.

Perhaps the best means of understanding how the rendering engine works is to watch an Echo2 application run in "Debug Mode", which causes all the XML synchronization messages to be displayed on screen. Debug Mode can be enabled by appending "?debug" to the URL of an Echo2 application. You can see this for yourself by visiting the "Interactive Test" application here: http://demo.nextapp.com/InteractiveTest/ia?debug (Please note that running in Debug Mode will cause a SUBSTANTIAL performance degradation.)

All web rendering is performed behind the scenes of Echo2's entirely Java-based user-interface toolkit. The end-developer need only be concerned with the server-side representation of the user-interface. Echo's "Web Application Container" monitors the state of the component hierarchy and takes care of all communication with the client browser. The Application Container is responsible for processing synchronization messages from the client, and notifying the server-side application of user actions via plain Java events. When modifications are made to the server-side hierarchy of components representing an instance of the user-interface, the Application Container translates these changes into an efficient synchronization message sent to the client to bring its state up to date with the server.

The current release of Echo2 is 2.0 Alpha 3. Please understand that Echo2 is currently in the alpha stage and is under heavy development. We welcome input and participation in the project. Please visit http://www.nextapp.com/products/echo2 for more information and downloads. Our Echo community developer forums are also available at http://forum.nextapp.com.