Learning AJAX
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This is a two-part article. In these two parts I'll try to describe what AJAX is, and how to use AJAX in PHP and JSP. Later we will use some advanced JSP tag libraries to make cool AJAX-based web applications.
Please remember, AJAX is not a new programming language, so you don't have to learn anything new. AJAX involves just using the existing standards (JavaScript and XML) in a different way. AJAX became popular because of Google in 2005. AJAX becomes a common ingredient in web 2.0-based web applications.
Why do we need AJAX? Often web-based applications are not as user-friendly as desktop applications. Using AJAX, we can create a feature-rich and easy-to-use graphical user interface for web applications. AJAX is supported by most of the web browsers available today.
Using AJAX technology we can get information from a server in the background without reloading the web page. AJAX uses HTTP requests for this. With AJAX, JavaScript communicates directly with the server, using an XMLHttpRequest object. This object makes XML requests over HTTP protocol. After getting the response from the server, new information can be placed in the current web page without reloading it. This XMLHttpRequest object is supported in Internet Explorer 5.0+, Safari 1.2, Mozilla 1.0 / Firefox, Opera 8+, and Netscape 7.
First we need to create an XMLHttpRequest object. Then using this object, we will request a web page from the server. JavaScript will then monitor the change of state of the request. If the request is complete and the response is successful, then the content from the web page requested will be returned as the response. This response can be in either of two formats, String or XML. Then we can use the response in your web pages. Next we will go into these steps in detail.
Next: The XMLHttpRequest Object >>
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