Sonntag, August 21, 2005

Application Aspects

The examples on AJAX I’ve published up to now, had to point out special aspects of the technical design and the implementation. They correspond to the "Bottom UP" method and are about the base components Javascript, XMLHTTP, XML and the asynchronous processing - the aspects That giva AJAX its name.

However, it is not the goal to play some technological games but to realize, improved or modernized a complete application with the assistance of the AJAX engine. The use of AJAX technologies fortunately does not need any principle proceeding at the level of the application but starts at the level of components.

Integration of AJAX components

In some cases we can integrated a functionality which is based on AJAX into an existing web application to better solve the problem of a component.

The LookUp example can be used e.g. in conventional web form and the background validating of the content of a HTML form can be guide the user before a regular positing of the form data.

The amount of JavaScript code that has to be loaded on the client is only about 18 kByte for the AJAX engine and the additional code for handling the selection list not very large.

It helps however to save a multiple this size since the data portion does not have to be sent completely to the client and the multiple reloading of the pages saves several times. AJAX based components particularly develop their largest advantages and it is importantly to have easy integrable components.

AJAX controls

When building new pages it is again a big advantage if the realization does not have to be made on each individual page on a very much detailed level. Here we prefer pre-fabricated components side by side with regular HTML objects to build up the final page.

To reach a high percentage of reusability those components are realized outside of the individual pages and are parameterized for their concrete usage.

HTML is used for the description of the appearance of the controls and JavaScript for the implementation of the behaviour. The binding of Javascript methods to the HTML objects is offerend by the Internet Explorer (*.htc) and by the Mozilla/Firefox (*.xbl) however in very different implementations that would lead into a double implementation. I use therefore a simple but compatible binding.

ASP.NET and AJAX controls

My choice to realize a collection of AJAX capable control falls on ASP.NET and the built-in user controls. These components are easy to implement and adapt. They offer already enough possibilities compared with Web Controls that must be implemented as classes. In addition to ASP.NET 1.1 they can also be compiled completely with ASP.NET 2,0

Building a complete new framework is not my intention because there are already some very useful frameworks that permit building component-based web applications.

Because the controls to be implemented are substantially based in HTML and JavaScript they do not really use the ASP.NET functionalities available on the server. Only building up the HTML code of a page from components will needed and this can also to be done by other tag libraries of other environments.

The advantage of ASP.NET is beside that is the simple realization of Web services.

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