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Machine Learning : Article

What Is AJAX?

AJAX isn't a technology, or a language, and there's no recipe to implement it

(October 7, 2005) - AJAX isn't a technology, or a language, and there's no recipe to implement it; it's just a combination of various components to achieve something you otherwise couldn't: asynchronous http requests. However, since early 2005, when Google and Flickr popularized the concept, its use has grown rapidly.

The name AJAX is short for Asynchronous JavaScript and XML. It uses the JavaScript XMLHttpRequest function to create a tunnel from the client's browser to the server and transmit information back and forth without having to refresh the page. The data travels in XML format because it transmits complex data types over clear text.

AJAX uses XHTML for the data presentation of the view layer, DOM, short for Document Object Model, which dynamically manipulates the presentation, XML for data exchange, and XMLHttpRequest as the exchange engine that ties everything together.

Because of these requirements, AJAX works on I.E. 5.0+, Mozilla 1.0+, Firefox 1.0+, Netscape 7.0+, and Apple added it to Safari 1.2+.

Traditional HTML sends a request to the server, which processes it and either returns a static HTML page or dispatches the request to some scripting language such as ColdFusion, which creates and returns an HTML page for the browser to render. When this method has to retrieve new data from the server it has to repost and reload another HTML file. In many cases perhaps only a small portion of the returned HTML code varies and the shell itself remains the same resulting in huge overhead because the data has to be downloaded every time.

Some classic examples of applications that would benefit from AJAX are searching for information and displaying it back in a table, related select dropdowns, or checking if a user exists before submitting an entire form.

As we can see, AJAX offers many advantages over traditional HTML applications, but we shouldn't overestimate it. Because the data is JavaScript-driven, one of the main drawbacks is that search engines won't index any of the dynamically generated content. It's definitely not SEO-friendly.

People familiar with MVC will have a better grasp of the concept. Though details of MVC are outside of the scope of this article, the three defined components are Model, View, and Controller. The controller mediates between the data model and the view. It responds to events, which are usually actions by users, and changes the view or model as appropriate. The view consists of the HTML. JavaScript reacts to events triggered by the user and alters the existing rendered content with DOM. ColdFusion will be our model layer and can consist of one or more files.

Building an AJAX platform or engine from scratch can be a difficult and lengthy procedure. There are many AJAX engines available for download and you're welcome to use any of them. The only difference between implementations will be the data encoding, transmission, and decoding methods. The views and models of the MVC will be the same. My examples will be based on CFAJAX, a community-driven Open Source project. One of the problems with CFAJAX is its poor documentation. There is no manual or even a complete FAQ. So I will explain how to set it up step-by-step and work around its downside.

To use AJAX you'll need to really know JavaScript and DOM. But by the end of this article you'll be able to set up AJAX, a ColdFusion model, make basic calls, and exchange simple data. As the applications grow and become more complex, the AJAX engine will remain the same, and the CF model will have more functions, but your JavaScript will have to manipulate more and more objects and that's where it's really at.

Enough chatter, let me show you how it works.

First, go to www.indiankey.com/cfajax/project.asp and download cfajax.1.2.zip (see AjaxCFC for an improved framework). This file contains the core engine, some utilities, and some examples. Let's set up a folder in your Web root or whatever accessible folder you like called 'ajax.' Put the 'core' folder located in the cfajax zip file inside your 'ajax' folder. There are only two important files in this folder: 'engine.js' and 'cfajax.cfm.'

The engine.js contains the whole AJAX object that we'll use as our tunnel and cfajax.cfm has some basic functions that your ColdFusion model will have to include to decode the AJAX packet. Other files, not so core anymore, are 'util.js.' which contains a series of DOM functions to facilitate HTML manipulation when the server response is received, 'rico.js,' used for a built-in accordion example, and 'settings.js,' which aren't really settings, only the location of your ColdFusion model and an error-handler function. The only reason why this file exists is to hide the location of your ColdFusion file should someone open and view the source of your HTML file, which in my opinion is counter-productive because you have to edit this file and add a location variable every time you want to use AJAX with different models. The security should be built into the ColdFusion file.

Some people will claim that they can provide you with AJAX functionality without writing a single line of JavaScript; I disagree. Although you could use ColdFusion libraries to generate JavaScript, the results will be limited to the functionality provided. AJAX means asynchronous JavaScript and XML, not ColdFusion. So if you want to use AJAX effectively and provide solutions to new problems, you should learn JavaScript.

Now that we have our CFAJAX in place, let's create an index.cfm file and a model.cfm file in your ajax folder. For larger applications I would store the views in a 'views' folder and models in a 'models' folder, but I digress. Shall we concentrate on the basic example?

Open index.cfm and include the 'core/engine.js' file. Then create a 'getGreetings' and 'getGreetings_result' function. We'll call getGreetings onLoad for now, and the results function will just alert the response.

The 'engine.js' file creates an object called DWREngine; it means Direct Web Remoting. We will mainly be using a method called '_execute.' Execute takes four or more arguments. The first argument is the ColdFusion model location, then a queryString, a methodName, and a callback function, which is the JavaScript function that will be called when we get a response from the server. Execute also takes some optional arguments. It's not documented, but Execute will take any number of arguments, which will be parameters to be passed to the called method, and they have to be put between the third and fourth argument. I'll show you an example later.

Right now the file looks like this:

Our model.cfm will be extremely simple. All we need to do is include the 'core/cfajax.cfm' file and a getGreetings function:

model.cfm
<cfinclude template="core/cfajax.cfm">
<cffunction name="getGreetings" returntype="string">
  <cfreturn "Today is " & DateFormat(now(),'MMMM DD') & ", Greetings." />
</cffunction>

Well, that was easy; we just finished our first AJAX application.

More Stories By Rob Gonda

Rob Gonda is an industry visionary and thought leader, speaks on emerging technologies conferences nationwide, and combines unique approaches to technology and marketing strategies. As a head of Creative Technologies at Sapient, Gonda is an interactive technical “guru,” who provides the knowledge and experience required to run high-level, multi-channel interactive campaigns that reach millions of consumers. Gonda has more than 15 years of experience in web development and 360 marketing campaigns for clients such as Coca-Cola, Adobe, Guinness, Toyota, Taco Bell, NBC, and others. His areas of specialty include emerging technologies, marketing strategy, social media, digital out-of-home, mobile, behavioral targeting, and multi-channel synergy. Before joining the strategy and technology leadership teams at Sapient, Gonda was co-founder and chief technical officer at iChameleon, a Hollywood FL-based agency renown for its emerging experiences and creative technology. In addition to his agency work, Gonda the chair for the digital media council at the Advertising Research Foundation, is the former editor-in-chief of the AJAX Developer’s Journal, co-author of “Real-World AJAX: Secrets of the Masters”, a passionate blogger who authors www.takemetoyourleader.com, and contributors to various publications such as Ad Age and Ad Week. He is a frequent figure on the speaker circuit, having presented at conferences from the senate’s CIO emerging technology to SXSW and Omma. Rob’s mission is to develop forward-thinking expertise that will ensure clients are always on par with rapidly changing technologies and maintain its ethos of evolving. You can reach him at rob[at]robgonda[dot]com and read his blog is at http://takemetoyourleader.com

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Most Recent Comments
Swamy 04/21/08 03:57:36 PM EDT

Hi, I need a basic clarification. will Ajax can be implemented in ColdFusion 5 version(on IIS/oracle 9i). If yes, please help me by providing some information like How to setup engine files and how to get it worked in CF5.

karthikeyan Palani 01/20/08 03:21:17 AM EST

Hi Rob,
Thank you for the introduction for ajax with coldfusion .It is very easy to get started.

Hello Ajaxer 09/10/07 10:07:01 PM EDT

did u recognize the Ajax interface as you posted your feedback, or you have no clue what Ajax means?

ajaxer 09/10/07 09:36:31 PM EDT

too bad you didnt use AJAX on this site...

SYS-CON Brazil News Desk 04/06/06 10:25:25 AM EDT

It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999. Enjoy Rob Gonda's highly popular ColdFusion Developer's Journal article on AJAX, the hottest software development of 2005, with plenty more heat promised for 2006.

news desk 02/13/06 08:41:32 PM EST

It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999. Enjoy Rob Gonda's highly popular ColdFusion Developer's Journal article on AJAX, the hottest software development of 2005, with plenty more heat promised for 2006.

Rob Gonda 01/23/06 01:35:58 AM EST

Neither FF or IE will allow cross-domain scripting.

This is a securiry risk, read more here:
http://getahead.ltd.uk/ajax/cross-domain-xhr

There are ways around it like a Server Side proxy, or third party JavaScripts like Ajax Extend (http://ajaxextended.com/)

-Rob

Morgan 01/23/06 01:21:16 AM EST

Ok had a little time to kill and decided I'd give Ajax a try and see what all the hype was about. Downloaded and installed cfAjax folowed install directions step by step. all seemed fine untill I tried to run one of the sample applications. Then I got the following error.

Permission denied to call method xmlhttpRequest.open

I decided to load a full version of ajax and still got same error In looking for an answer I keep seeing the following as the culprit with no real solution.

This error occurs when you try to make requests off-domain.

which in pouring over the code I cant find anywher that the examples are making calls to off-domain. So lets cover the basics..

yes error is same in both ie and moxilla

no I'm not using a local file (ie //file/ajax/example)

no I dont have a firewall running between my work station and my development server

yes both machines are windows running IIS

yes the url has http (ie http://myDevelopmentServer/ajax/examples/text.htm

yes I created a virtual host for ajax in both IIS and my CF Administrator

So I guess that covers it Any help would be great

Robert Blackburn - DevBlog 01/17/06 09:52:59 PM EST

Trackback Added: What Is AJAX?; While I am on the topic of CFDJ articles, there is another one titled What Is AJAX?. This one begins a lot like my earlier p...

Baz Web Development: Ajax, FastCGI, Joomla 12/31/05 05:34:46 AM EST

Trackback Added: Another “What Is Ajax” Introduction; What Is Ajax?
— It’s become very popular lately, even though it’s not exactly new. It’s been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999. Enjoy Rob Gonda’s highly popu...

Rob Gonda 12/24/05 01:51:46 AM EST

Mohan, I am glad I could help; I definitely tried to make the article so easy and straight forward so everyone can get AJAX started. This will be one of the major topics for 2006.

To stay up to date with AJAX, please check my blog (www.robgonda.com) http://www.robgonda.com

Best,

-Rob

mohan 12/23/05 08:20:53 PM EST

i am new to AJAX this is a wonderful article. After seeing this article i am going to implement CFAJAX in our (production) search form.

thank you veryyyyyyyyyy much

regards mohan

Rob Gonda 12/15/05 11:56:06 PM EST

Perhaps, nothing really prevented anyone from using it; Jesse James Garrett just had to come up with the idea/concept. By the way, don't miss Jesse at the Ajax Seminar (www.ajaxseminar.com/)

Rob Gonda 12/14/05 09:25:12 PM EST

It is indeed; AJAX involves combining any server scripting language with client side, hence, JavaScript. I can see how you could probably automate a two related select boxes without writing JavaScript, but certainly not an RIA or Web 2.0 application.

Editor 12/14/05 06:53:44 PM EST

SYS-CON will soon launch a dedicated online AJAX section but it will not be called "AJAX Developer's Journal" or "AJAX Magazine." Thanks and best regards.

P.S. Please stay tuned for SYS-CON's complete educational offerings to be announced soon.

Rob Gonda 12/13/05 10:54:35 PM EST

I just looked at the source code attached to the article, and you're right, it's missing model.cfm.
You may download the complete source code at
http://www.robgonda.com/blog/index.cfm/2005/11/17/CFJD-Article-2

no comment 12/13/05 04:50:31 PM EST

I have cfajax working, but your example model.cfm doesn't do anything. What am I doing wrong?

news desk 12/11/05 08:17:11 PM EST

So What's AJAX? (Part One of Two) It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999.

ajax 12/11/05 05:09:45 PM EST

So What's AJAX? (Part One of Two)
It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999.

So What's AJAX? 12/11/05 05:01:05 PM EST

So What's AJAX? (Part One of Two)
It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999.

CFDJ News Desk 12/11/05 04:41:45 PM EST

So What's AJAX? (Part One of Two) It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999.

Rob Gonda 12/09/05 12:34:48 AM EST

by the way, check out my latest alternative to cfajax. I developed an ajax CFC framework.

check it out at http://www.robgonda.com/blog/projects/ajaxcfc/

Rob 11/26/05 07:06:09 PM EST

For more information please visit http://www.robgonda.com/blog

Rob 11/22/05 11:46:03 PM EST

Just testing this feedback again... Trying to find out exactly what's happening.

ColdFusion Developer's Journal News Desk 10/27/05 09:13:41 PM EDT

So What's AJAX? It's become very popular lately, even though it's not exactly new. It's been possible to use the concept behind AJAX since browsers introduced the XMLHttpRequest function in 1999.

Rob 10/27/05 08:40:25 PM EDT

I already wrote and submitted the second part of the article. It gets more in depth and provides lots of code examples.

Cheers

Rob 10/27/05 08:38:08 PM EDT

Adam, I cannot help you with FB as I really dont use it much. I built my own MVC framework, but I was an active model-glue user. I can help you with MG or MII frameworks if it works for you.

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