AJAX

Hi Friends,



Today I will be talking about Ajax. Ajax (asynchronous JavaScript and XML), or AJAX, is a group of interrelated web development techniques used for creating interactive web applications or Rich Internet Applications.
With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. Data is retrieved using the XMLHttpRequest object or through the use of Remote Scripting in browsers that do not support it.

Technologies


The term Ajax has come to represent a broad group of web technologies that can be used to implement a web application that communicates with a server in the background, without interfering with the current state of the page. Ajax uses certain technologies like:

- XHTML and CSS for presentation
- the Document Object Model for dynamic display of and interaction with data
- XML and XSLT for the interchange and manipulation of data, respectively
- the XMLHttpRequest object for asynchronous communication
- JavaScript to bring these technologies together


There have been a number of developments in the technologies used in an Ajax enabled application, these are:


- JavaScript is not the only client-side scripting language that can be used for implementing an Ajax application. Other languages such as VBScript are also capable of the required functionality.


- The XMLHttpRequest object is not necessary for asynchronous communication. It has been noted that IFrames are capable of the same effect.


- XML is not required for data interchange and therefore XSLT is not required for the manipulation of data. JavaScript Object Notation (JSON) is often used as an alternative format for data interchange.


Ajax Framework


An Ajax framework is a framework that helps to develop web applications that use Ajax, a collection of technologies used to build dynamic web pages on the client side. Data is read from the server or sent to the server by JavaScript requests.


Ajax frameworks can be loosely grouped into categories according to the features they offer and the skills required of the user:


Direct Ajax frameworks


These frameworks require HTML, CSS and Ajax expertise: a developer is expected to author pages directly in HTML, and framework APIs deal directly with HTML elements. These frameworks are generally smaller. They are commonly used for a web site such as a shopping experience, but not for a web application such as web-based email, at least not without further frameworks layered on top.


Ajax component frameworks


These frameworks offer pre-built components, such as tabbed panes, which automatically create and manage their own HTML. Components are generally created via JavaScript or XML tags, or by adding special attributes to normal HTML elements. These frameworks are generally larger, and intended for web applications rather than web sites.


Server-driven Ajax frameworks


Several frameworks offer a server-side component-based development model with some degree of Ajax support. Components are created and manipulated on the server using a server-side programming language. Pages are then rendered by a combination of server-side and client-side HTML generation and manipulation. User actions are communicated to the server via Ajax techniques, server-side code manipulates a server-side component model, and changes to the server component model are reflected on the client automatically.


Advantages


- In many cases, the pages on a website consist of much content that is common between them. Using traditional methods, that content would have to be reloaded on every request. However, using Ajax, a web application can request only the content that needs to be updated, thus drastically reducing bandwidth usage.


- The use of asynchronous requests allows the client's Web browser UI to be more interactive and to respond quickly to inputs, and sections of pages can also be reloaded individually. Users may perceive the application to be faster or more responsive, even if the application has not changed on the server side.


- The use of Ajax can reduce connections to the server, since scripts and style sheets only have to be requested once.


Ajax is widely used in web applications developed in Java and .Net platform. Professionals working on these platforms/technologies can incorporate Ajax for better performance of their applications.


Happy Learning!!...


Cheers


Madhu S