Web 2.0 and AJAX
Abhishek Nagar
nagar.ksp@gmail.com

Agenda
• Definitions: Web 2.0 , AJAX
• AJAX : Real Life Examples
• Why AJAX?
• Technologies used in AJAX
– XMLHttpRequest
• Steps of AJAX Operation
• AJAX Security

A little Web History
• CGI / Perl & C
• Servlets
• JSP / ASP / PHP
• Java Based frameworks
– Struts, JSF & many others
• Other Scripting
– Python, Ruby
• But all these kept the same (1.0) UI

Web 2.0 by examples
Web 1.0 Web 2.0
• •
Double Click Google Adsense
• •
Ofoto Flickr
• •
Britannica Online Wikipedia
• •
Personal Websites Blogging
• •
Directories Social Web

Web 2.0 by definitions
• Not just a technology
• Web as a platform
• Collective Intelligence
• Data is key and should be shared
• Lightweight Programming Models
• The network is the computer
• Rich User Experience
• Largely driven by hobbyists

So what is WEB 2.0
• Technologies
– Blogging, Wikis
– AJAX, Rich Internet clients
• Attitudes
– Sharing, Connected, Participatory
– Services, Users Engaged
• Services
– Flickr, BitTorrent
– Maps, Wikipedia
– Google, Yahoo etc
• Drivers
– Faster Connectivity
– More available connectivity
– More powerful machines
– Customers More Comfortable with Technology
– Browser wars (almost) over

AJAX
Asynchronous Javascript + XML
• DHTML plus Asynchronous communication
capability through XMLHttpRequest
• Pros
– Most viable technology so far
– Tremendous industry momentum
– Several toolkits and frameworks are emerging
– No plug-in required
• Cons
– Still browser incompatibility
– JavaScript is hard to maintain and debug
neither new, nor a technology

AJAX : Real Life Examples
• Google Maps
– http://maps.google.com/
• Google Suggest
– http://www.google.com/webhp?complete=1&hl=en
• Gmail
– http://gmail.com/
• Yahoo Maps (New)
– http://maps.yahoo.com/
• Wikipedia
– http://en.wikipedia.com/
• Many many more

Why AJAX?
• Intuitive and natural user interaction
– No clicking required
– Mouse movement is a sufficient event trigger
• \"Partial screen update\" replaces the \"click, wait,
and refresh\" user interaction model
– Only user interface elements that contain new information
are updated (fast response)
– The rest of the user interface remains displayed without
interruption (no loss of operational context)
• Data-driven (as opposed to page-driven)
– UI is handled in the client while the server provides data

Why AJAX?
• Asynchronous communication replaces
synchronous request/response model.
– A user can continue to use the application while the client
program requests information from the server in the
background
– Separation of displaying from data fetching

Technologies Used in AJAX
• Javascript
• DOM
• CSS
• XMLHttpRequest

XMLHttpRequest
• Javascript
• Adopted from modern browsers
– Mozilla, Safari and Opera
• Communicates with a server via standard HTTP
GET/POST
• XMLHttpRequest object works in the background for
performing asynchronous communication with the
backend server
– Does not interrupt user operation

Browsers which support
XMLHttpRequest
•Mozilla Firefox 1.0 and above
•Netscape version 7.1 and above
•Apple Safari 1.2 and above.
•Microsoft Internet Exporer 5 and above
•Konqueror
•Opera 7.6 and above
and many more

Classic Vs. AJAX Model

Classic Model
Interrupted user operation
while the data is being fetched

The AJAX Model
Uninterrupted user operation
while the data is being fetched

Steps of AJAX operation
• A client event occurs
• An XMLHttpRequest object is created
• The XMLHttpRequest object is configured
• The XMLHttpRequest object makes an async. Request
• The Validate Servlet returns an XML document containing
the result
• The XMLHttpRequest object calls the callback() function and
processes the result
• The HTML DOM is updated

AJAX Security : Server Side
• AJAX-based Web applications use the
same server side security schemes of
regular Web applications
• AJAX-based Web applications are
subject to the same security threats as
regular Web applications

AJAX Security : Client Side
• JavaScript code is visible to a
user/hacker
• JavaScript code is downloaded from the
server and executed at the client

Thank You
Abhishek Nagar