This document provides an introduction to AJAX (Asynchronous JavaScript and XML) web technology. It defines AJAX as a technique for creating interactive web applications using small asynchronous data exchanges in the background without reloading the entire web page. The document outlines AJAX and provides examples of its real-world uses. It then explains how AJAX works by making HTTP requests in the background using the XMLHttpRequest object and JavaScript handlers. Code samples are included to demonstrate implementing AJAX.

1. Web Technology Introduction
Collin Smith (Dec. 16, 2006)
AJAXAJAX

2. AJAX OutlineAJAX Outline
 What is AJAX?
 Benefits
 Real world examples
 How it works
 Code review
 Samples

3. What is AJAX?What is AJAX?
 Asynchronous JavaScript and XML(AJAX)
 Web development technique for creating web applications
 Makes web pages more responsive by exchanging small
amounts of data
 Allows the web page to change its content without
refreshing the whole page
 A web browser technology independent of web server
software

4. BenefitsBenefits
 Improves the user experience
 Analyzing information typed into browser in real time
 Provide a richer experience
 Increases responsiveness of web pages
 Improve bandwidth utilization
 Only data which is required is retrieved from the server

5. Real World ExamplesReal World Examples
 Google Maps (http://maps.google.com/) (slidable maps)
 My Yahoo! (http://my.yahoo.com/) (shuffling windows)

6. How it worksHow it works
 AJAX runs in your browser
 Works with asynchronous data transfers(HTTP requests)
between the browser and the web server
 Http requests are sent by javascript calls without having to
submit a form
 XML is commonly used as the format for receiving server
data but plain text may be used as well

7. 1 – XMLHttpRequest object1 – XMLHttpRequest object
 A page element must make a javascript call
 The javascript function must create an XMLHttpRequest
object which is used to contact the server
 Javascript must determine whether the client is IE or
Firefox
 http = new ActiveXObject("Microsoft.XMLHTTP"); (IE)
 http = new XMLHttpRequest(); (Mozilla)

8. 2 - Sending the request2 - Sending the request
 Once the XMLHttpRequest object has been created it must
be set up to call the server
 http.open("GET", serverurl, true);
 http.onreadystatechange = jsMethodToHandleResponse;
 http.send(null);
 The code above utilizes the XMLHttpRequest object to
contact the server and retrieve server data
 When the response returns the javascript method
jsMethodToHandleResponse can update the page

9. 3 - Handling the Response3 - Handling the Response
 Implementation of the javascript method which will be used
to handle the response (Event Handler)
 function jsMethodToHandleResponse(str)
 {
 //simply take the response returned an update an html
element with the returned value from the server
 document.getElementById("result").innerHTML = str;
 }
 Now the page has communicated with the server without
having to refresh the entire page

10. readyState propertyreadyState property
 The XMLHttpRequest readyState property defines the
current state of the XMLHttpRequest object
 Possible values for the readyState
 Usually we are usually only concerned with state 4
State Description
0 The request is not initialized
1 The request has been setup
2 The request has been submitted
3 The request is in process
4 The request is completed

11. Sample CodeSample Code
 Simply unzip the sample code into a JSP Location and go
to index.jsp
 There are various examples that show some AJAX
functionality
 It is all JSP to make it easy to setup and easy to see the
code.
 The JSPs are generic enough to be easily to converted to
other technologies (.NET or PHP)

12. ReferencesReferences
 http://en.wikipedia.org/wiki/Ajax_%28programming%29
 http://www.w3schools.com/ajax/default.asp