Thursday, June 7, 2007

Ajax good interms of UI and Response

As J2EE developers, it seems we are constantly focused on "backend mechanics." Often, we forget that the main success of J2EE has been around the Web application; people love developing applications that utilize the Web for many reasons, but mainly because the ease of deployment allows a site to have millions of users with minimal cost. Unfortunately, over the years we have invested too much time in the back end and not enough time in making our Web user interfaces natural and responsive to our users.

The key lies in the combination of browser-side JavaScript, DHTML, and asynchronous communication with the server. This article also demonstrates just how easy it is to start using this approach, by leveraging an Ajax framework (DWR) to construct an application that communicates with backend services directly from the browser. If used properly, this tremendous power allows your application to be more natural and responsive to your users, thereby providing an improved browsing experience.

Introduction

The term Ajax is used to describe a set of technologies that allow browsers to provide users with a more natural browsing experience. Before Ajax, Web sites forced their users into the submit/wait/redisplay paradigm, where the users' actions were always synchronized with the server's "think time." Ajax provides the ability to communicate with the server asynchronously, thereby freeing the user experience from the request/response cycle. With Ajax, when a user clicks a button, you can use JavaScript and DHTML to immediately update the UI, and spawn an asynchronous request to the server to perform an update or query a database. When the request returns, you can then use JavaScript and CSS to update your UI accordingly without refreshing the entire page. Most importantly, users don't even know your code is communicating with the server: the Web site feels like it's instantly responding.

While the infrastructure needed by Ajax has been available for a while, it is only recently that the true power of asynchronous requests has been leveraged. The ability to have an extremely responsive Web site is exciting as it finally allows developers and designers to create "desktop-like" usability with the standard HTML/CSS/JavaScript stack.

Traditionally in J2EE, developers have been so focused on developing the service and persistence layers that the usability of the user interface has lagged behind. It is common to hear phases such as, "we don't have time to invest in the UI" or "you can't do that with HTML" during a typical J2EE development cycle. The following Web sites prove that these excuses don't hold water any longer:

* BackPack
* Google Suggest
* Google Maps
* PalmSphere

AJAX stands for...

Ajax isn't a technology. It's really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:

  1. Standards-based presentation using XHTML and CSS
  2. Dynamic display and interaction using the Document Object Model
  3. Asynchronous server communication using XMLHttpRequest
  4. JavaScript binding everything together

This is all fine and dandy, but why the name Ajax? Well, the term Ajax was coined by Jesse James Garrett, and as he puts it, it is "short-hand for Asynchronous JavaScript + XML."


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