Click here to close now.

Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Maureen O'Gara, Nancy Y. Nee, Tad Anderson, Daniel Kaar

Related Topics: ColdFusion, Adobe Flex, AJAX & REA

ColdFusion: Article

ColdFusion and AJAX

All this is done without any screen refreshes. You have to admit that the interface is pretty sweet

One of the most annoying things about the Web page paradigm is that you have to reload the page whenever you want to do something on the server side. If you want to do a site search, it's sprinkled across two pages.

On the first page, the user will enter a search term, then clicks a submit button to get to the second page where the search results are returned. If the user wants to filter or sort the search results it's usually refreshed again and each result is redisplayed in its filtered state.

Lately there's been a movement to help improve the Web by eliminating these constant page refreshes. Macromedia's Rich Internet Application (RIA) push with Flash and Flex has been at the forefront of this effort, however Flex' entry price has made it prohibitive for many ColdFusion Developers. That's where AJAX comes in. It's an alternate way to create a RIA and relies on technologies built into most browsers, making it completely free.

Dissecting AJAX
AJAX stands for Asynchronous JavaScript and XML. It's not a single technology, but rather a combination of different technologies that are used to create a Rich Internet Application feel. You've probably seen examples of this kind of application. Google uses AJAX a lot on such services as maps.google.com. After bringing up a location, you can click and drag the map, zoom in or out, or even bring up directions to and from the location. All this is done without any screen refreshes. You have to admit that the interface is pretty sweet. (Note: Yahoo has a similar mapping application, built entirely in Flex at http://maps.yahoo.com/beta.)

Since AJAX is a combination of technologies you're going to want to know what you're getting into before going any farther, right? I thought so. Here's the list:

  • XHTML: To start with you need a display language. Most resources on AJAX say you have to use XHTML, but regular HTML will work too.
  • XMLHttpRequest: The XMLHttpRequest object lets you retrieve data from the server without refreshing the page. It's a JavaScript object implemented in most major browsers. As the XMLHttpRequest object is being called, the user can do other things on the page. This is where the "asynchronous" part of the acronym comes in.
  • iFrames: iFrames are in-line frames and are sometimes used as an alternative to the XMLHttpRequest object. A regular frame will divide the browser window into multiple separate pages, but an in-line frame embeds one page inside another. I won't get into any iFrames details in this article.
  • XML: You all know what XML is, right? As a refresher, it's a way to describe data. If you need more details, read the article in this column from August 05 at http://coldfusion.sys-con.com/read/117667.htm.
  • Document Object Model: The document object model defines your HTML page through a programmer API.
  • JavaScript: I'm sure you all know what JavaScript is too. It's the most common language used for providing client-side functionality to HTML pages.
How do all these different technologies work together using AJAX? Well, it generally works something like this:
  1. First, the user comes to your page and the page loads. Something (depending on what your page does) is loaded and displayed to the user.
  2. The user does something such as clicking a link. Instead of reloading the page (as would happen in a normal Web app), that link fires off a JavaScript function.
  3. The JavaScript function uses XMLHttpRequest object to retrieve XML data from the server.
  4. Then the JavaScript parses the XML Data and through the Document Object Model will change the page without a refresh.
So the user gets to see more data quicker without the annoying page refreshes. That's fantastic, right? Why isn't everyone using this? Well, as with all things, AJAX isn't perfect. There are drawbacks:
  • Development Time: Working with AJAX will bring you back to the old days of Web development, especially if you want any kind of cross-compatibility. There are different syntaxes for creating the XMLHttpRequest object in IE vs Netscape/Firefox, which can lead to extended development times.
  • User Experience: When used properly, an AJAX can enhance the user experience. However, when used improperly it can make it horrendous. Since the page isn't reloading, what happens when the user hits the back button? He'll leave the application altogether. I bet he expected to go to the app's "previous state." What happens when the user bookmarks a page? He'll go the "initial" state of the app. There are workarounds, of course, but they're not trivial to implement.
  • Searches: The single-page nature of the app makes indexing by search engines a tetchy proposition at best.
  • Response Times: The very thing that works for you (no page reloads) can also work against you. What happens if you're retrieving a lot of data from the server? And the user is given no indication that something is happening.
  • JavaScript: JavaScript must be enabled for an AJAX app to work. If JavaScript is disabled, your user isn't going to have a lot of fun with an AJAX app.
  • Accessibility: AJAX is, most likely, not going to meet accessibility guidelines. If this is a goal of your project you're going to have to provide a fallback option. That means developing two paths to the same goal.
There are a few real simple examples of AJAX that you've probably used or seen that existed long before the term AJAX was conceived. Have you ever rolled your mouse over a graphic navigation button only to have that graphic change? JavaScript rollovers can be considered a precursor to AJAX. They do use JavaScript and they do change the state of the page. Have you turned on or off a DHTML layer on a page based on some selection by the user? This is another example of AJAX. If an application has a select box with an "other" option in it I'll often use DHTML to display an input text box if "other" is selected. If other isn't selected the input box is hidden. Both of these are simple examples of changing the page without a screen refresh. They don't go out to the server to get data, but they still fit the RIA paradigm.

Putting This All Together
Let me show you how this all comes together, so you can actually do something useful. The first step in the process is to initialize the XMLHttpRequest object. Unfortunately, there's not consistent way to do this across browsers:

<script language="javascript" type="text/javascript">
var request = false;
try {
    request = new XMLHttpRequest();
}
catch (trymicrosoft) {
   try {
    request = new ActiveXObject("Msxml2.XMLHTTP");
   }
   catch (othermicrosoft) {
   try {
    request = new ActiveXObject("Microsoft.XMLHTTP");
   }
   catch (failed) {
    request = false;
    }
   }
}
</script>

The first line initializes the request variable, giving it a Boolean value of false. You can check against this later to make sure that your request object was properly initialized. The next code creates an instance of the XMLHttpRequest object using 'new XMLHttpRequest.' This works fine for most non-Microsoft browsers, but won't work in IE. If it doesn't initialize, then an error is thrown, which is where the first catch statement comes into play. It attempts to re-initialize using the method available in the current version of Internet Explorer: new ActiveXObject("Msxml2.XMLHTTP").

If that fails, it tries the version from older versions of Internet Explorer new ActiveXObject("Microsoft.XMLHTTP"). That's kind of complicated right? I borrowed this initialization code from the article www-128.ibm.com/developerworks/Web/library/wa-ajaxintro2/?ca=dgr-lnxw07AJAX-Request (which you should all read because it goes into a lot more details about error checking that are outside the scope of this article).

So, now the code has created the object, but what can you do with it? As you can probably see, it doesn't do much yet. You want to assign it a URL, load the data, and then process the data in some way. This function will do that:

function getRSS() {
    var url = "/htdocs/jeffhousercom/wwwroot/rss.cfm";
    request.open("GET", url, true);
    request.onreadystatechange = updatePage;
    request.send(null);
}

This is function to grab an RSS feed. The first line defines the URL. This is standard JavaScript for defining a variable. You should bear in mind that you can only request URLs from the current Web site. In this case, I'm grabbing a RSS feed from a local copy of my blog. The next line calls a method on the request object entitled open. Open prepares the request to be sent, but doesn't actual send it. There are five arguments to the open function (although we only use three in this example):

  • Request-type: This specifies the request type, either get or post, for the URL that you want to send.
  • url: The URL specifies the URL that you're getting (or posting) to.
  • Asynchronous: The async value is a Boolean value that specifies whether this request is asynchronous or not. For AJAX use, you'll want to specify true. If set to false, the application will hold until this request is finished, which defeats the purpose of an RIA in the first place.
  • username: The username specifies the username required for accessing the URL, if applicable.
  • password: The username specifies the username required for accessing the URL, if applicable.
Okay, you've set up the request to be ready to send. The next line specifies the onreadystatechange property. This property specifies what function to call once the request is complete. If you don't specify a method to be called then nothing will happen once the request is complete. The final line calls the send method. The send method is the one that will execute the request. Its parameter is the data that you need to send along with the request. In our example, we aren't sending parameters, so we pass a null value.

Once the request complete, the updatePage function will execute, so lets look at that next:

function updatePage() {
   if (request.readyState == 4){
     Form1.XMLValues.value = request.responseText;
   }
}

This function first checks the readyState of the XMLHttpRequest object. Exploring that is beyond the scope of this article, but there are a lot more details in some of the references provided at the end. For now, all you need to know is that if the readyState is 4, then the request is complete. This takes the resulting value from the server response and assigns it to a form textbox. The form is below:

<form name="Form1">
    <textarea name="XMLValues" rows="20" cols="50"></textarea>
</form>

The text box will contain the XML from the RSS feed. There's another property associated with the XMLHttpRequest object called responseXML. This will contain the results as an XML Document object, which JavaScript can access natively. Unfortunately specific details are beyond the scope of this article, but I found this good resource to get you started on that: http://www.peachpit.com/articles/article.asp?p=29307&seqNum=4&rl=1 .

Where to Go from Here
If you want to learn more about AJAX, there are some great resources you can read. The article by Jesse James Garrett that started it all is at www.adaptivepath.com/publications/essays/archives/000385.php. Garrett is credited with coining the term AJAX. You can follow an AJAX blog at www.ajax-powered.net, which talks about all things AJAX. Finally, there are a few people who are working on ways to integrate ColdFusion and AJAX together. One is the CFAJAX project www.indiankey.com/cfajax. Another is the AJAXCFC project at www.robgonda.com/blog/projects/ajaxcfc.

More Stories By Jeffry Houser

Jeffry is a technical entrepreneur with over 10 years of making the web work for you. Lately Jeffry has been cooped up in his cave building the first in a line of easy to use interface components for Flex Developers at www.flextras.com . He has a Computer Science degree from the days before business met the Internet and owns DotComIt, an Adobe Solutions Partner specializing in Rich Internet Applications. Jeffry is an Adobe Community Expert and produces The Flex Show, a podcast that includes expert interviews and screencast tutorials. Jeffry is also co-manager of the Hartford CT Adobe User Group, author of three ColdFusion books and over 30 articles, and has spoken at various events all over the US. In his spare time he is a musician, old school adventure game aficionado, and recording engineer. He also owns a Wii. You can read his blog at www.jeffryhouser.com, check out his podcast at www.theflexshow.com or check out his company at www.dot-com-it.com.

Comments (5) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
walweb 10/30/06 02:37:09 AM EST

Nice example of a web2.0 application using Googlemaps API is PICSFROMSPACE, LOOKUP YOUR PLACE BY ADDRESS. Showing satellitepictures at streetlevel by address or zipcode.
Check out http://www.walweb.nl/picsfromspace

SEO/SEM Journal News Desk 10/29/06 02:12:13 PM EST

AJAX stands for Asynchronous JavaScript and XML. It's not a single technology, but rather a combination of different technologies that are used to create a Rich Internet Application feel. You've probably seen examples of this kind of application. Google uses AJAX a lot on such services as maps.google.com. After bringing up a location, you can click and drag the map, zoom in or out, or even bring up directions to and from the location. All this is done without any screen refreshes. You have to admit that the interface is pretty sweet. (Note: Yahoo has a similar mapping application, built entirely in Flex at http://maps.yahoo.com/beta.)

CFDJ News Desk 10/29/06 01:58:22 PM EST

AJAX stands for Asynchronous JavaScript and XML. It's not a single technology, but rather a combination of different technologies that are used to create a Rich Internet Application feel. You've probably seen examples of this kind of application. Google uses AJAX a lot on such services as maps.google.com. After bringing up a location, you can click and drag the map, zoom in or out, or even bring up directions to and from the location. All this is done without any screen refreshes. You have to admit that the interface is pretty sweet. (Note: Yahoo has a similar mapping application, built entirely in Flex at http://maps.yahoo.com/beta.)

CFDJ News Desk 10/29/06 01:15:39 PM EST

AJAX stands for Asynchronous JavaScript and XML. It's not a single technology, but rather a combination of different technologies that are used to create a Rich Internet Application feel. You've probably seen examples of this kind of application. Google uses AJAX a lot on such services as maps.google.com. After bringing up a location, you can click and drag the map, zoom in or out, or even bring up directions to and from the location. All this is done without any screen refreshes. You have to admit that the interface is pretty sweet. (Note: Yahoo has a similar mapping application, built entirely in Flex at http://maps.yahoo.com/beta.)

Dan Novik 10/17/06 07:46:05 AM EDT

a lot of Ajax components are part of Coldtags suite: http://www.servletsuite.com/jsp.htm#ajax

@ThingsExpo Stories
The WebRTC Summit 2014 New York, to be held June 9-11, 2015, at the Javits Center in New York, NY, announces that its Call for Papers is open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 16th International Cloud Expo, @ThingsExpo, Big Data Expo, and DevOps Summit.
GENBAND has announced that SageNet is leveraging the Nuvia platform to deliver Unified Communications as a Service (UCaaS) to its large base of retail and enterprise customers. Nuvia’s cloud-based solution provides SageNet’s customers with a full suite of business communications and collaboration tools. Two large national SageNet retail customers have recently signed up to deploy the Nuvia platform and the company will continue to sell the service to new and existing customers. Nuvia’s capabilities include HD voice, video, multimedia messaging, mobility, conferencing, Web collaboration, deskt...
The Open Compute Project is a collective effort by Facebook and a number of players in the datacenter industry to bring lessons learned from the social media giant's giant IT deployment to the rest of the world. Datacenters account for 3% of global electricity consumption – about the same as all of Switzerland or the Czech Republic -- according to people I met at the recent Open Compute Summit in San Jose. With increasing mobility at the edge of the cloud and vast new dataflows being predicted with the growth of the Internet of Things (and The Coming Age of Many Zettabytes) in the near...
Wearable technology was dominant at this year’s International Consumer Electronics Show (CES) , and MWC was no exception to this trend. New versions of favorites, such as the Samsung Gear (three new products were released: the Gear 2, the Gear 2 Neo and the Gear Fit), shared the limelight with new wearables like Pebble Time Steel (the new premium version of the company’s previously released smartwatch) and the LG Watch Urbane. The most dramatic difference at MWC was an emphasis on presenting wearables as fashion accessories and moving away from the original clunky technology associated with t...
SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborate. Cisco and our partners are building the platform for the Internet of Everything by connecting the...
15th Cloud Expo, which took place Nov. 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA, expanded the conference content of @ThingsExpo, Big Data Expo, and DevOps Summit to include two developer events. IBM held a Bluemix Developer Playground on November 5 and ElasticBox held a Hackathon on November 6. Both events took place on the expo floor. The Bluemix Developer Playground, for developers of all levels, highlighted the ease of use of Bluemix, its services and functionality and provide short-term introductory projects that developers can complete between sessions.
Temasys has announced senior management additions to its team. Joining are David Holloway as Vice President of Commercial and Nadine Yap as Vice President of Product. Over the past 12 months Temasys has doubled in size as it adds new customers and expands the development of its Skylink platform. Skylink leads the charge to move WebRTC, traditionally seen as a desktop, browser based technology, to become a ubiquitous web communications technology on web and mobile, as well as Internet of Things compatible devices.
SYS-CON Events announced today that robomq.io will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. robomq.io is an interoperable and composable platform that connects any device to any application. It helps systems integrators and the solution providers build new and innovative products and service for industries requiring monitoring or intelligence from devices and sensors.
The list of ‘new paradigm’ technologies that now surrounds us appears to be at an all time high. From cloud computing and Big Data analytics to Bring Your Own Device (BYOD) and the Internet of Things (IoT), today we have to deal with what the industry likes to call ‘paradigm shifts’ at every level of IT. This is disruption; of course, we understand that – change is almost always disruptive.
WebRTC is an up-and-coming standard that enables real-time voice and video to be directly embedded into browsers making the browser a primary user interface for communications and collaboration. WebRTC runs in a number of browsers today and is currently supported in over a billion installed browsers globally, across a range of platform OS and devices. Today, organizations that choose to deploy WebRTC applications and use a host machine that supports audio through USB or Bluetooth can use Plantronics products to connect and transit or receive the audio associated with the WebRTC session.
Docker is an excellent platform for organizations interested in running microservices. It offers portability and consistency between development and production environments, quick provisioning times, and a simple way to isolate services. In his session at DevOps Summit at 16th Cloud Expo, Shannon Williams, co-founder of Rancher Labs, will walk through these and other benefits of using Docker to run microservices, and provide an overview of RancherOS, a minimalist distribution of Linux designed expressly to run Docker. He will also discuss Rancher, an orchestration and service discovery platf...
SYS-CON Events announced today that Aria Systems, the leading innovator in recurring revenue, has been named “Bronze Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Proven by the world’s most demanding enterprises, including AAA NCNU, Constant Contact, Falck, Hootsuite, Pitney Bowes, Telekom Denmark, and VMware, Aria helps enterprises grow their recurring revenue businesses. With Aria’s end-to-end active monetization platform, global brands can get to market faster with a wider variety of products and services, while maximizin...
SYS-CON Media announced today that @WebRTCSummit Blog, the largest WebRTC resource in the world, has been launched. @WebRTCSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. @WebRTCSummit Blog can be bookmarked ▸ Here @WebRTCSummit conference site can be bookmarked ▸ Here
SYS-CON Events announced today that Alert Logic, the leading provider of Security-as-a-Service solutions for the cloud, has been named “Bronze Sponsor” of SYS-CON's 16th International Cloud Expo® and DevOps Summit 2015 New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY, and the 17th International Cloud Expo® and DevOps Summit 2015 Silicon Valley, which will take place November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA.
Sonus Networks introduced the Sonus WebRTC Services Solution, a virtualized Web Real-Time Communications (WebRTC) offer, purpose-built for the Cloud. The WebRTC Services Solution provides signaling from WebRTC-to-WebRTC applications and interworking from WebRTC-to-Session Initiation Protocol (SIP), delivering advanced real-time communications capabilities on mobile applications and on websites, which are accessible via a browser.
SYS-CON Events announced today that Vitria Technology, Inc. will exhibit at SYS-CON’s @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Vitria will showcase the company’s new IoT Analytics Platform through live demonstrations at booth #330. Vitria’s IoT Analytics Platform, fully integrated and powered by an operational intelligence engine, enables customers to rapidly build and operationalize advanced analytics to deliver timely business outcomes for use cases across the industrial, enterprise, and consumer segments.
SYS-CON Events announced today that Liaison Technologies, a leading provider of data management and integration cloud services and solutions, has been named "Silver Sponsor" of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York, NY. Liaison Technologies is a recognized market leader in providing cloud-enabled data integration and data management solutions to break down complex information barriers, enabling enterprises to make smarter decisions, faster.
SYS-CON Events announced today that Solgenia will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Solgenia is the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions. Designed to “Bridge the Gap” between Personal and Professional Social, Mobile and Cloud user experiences, our solutions help large and medium-sized organizations dr...
Connected devices and the Internet of Things are getting significant momentum in 2014. In his session at Internet of @ThingsExpo, Jim Hunter, Chief Scientist & Technology Evangelist at Greenwave Systems, examined three key elements that together will drive mass adoption of the IoT before the end of 2015. The first element is the recent advent of robust open source protocols (like AllJoyn and WebRTC) that facilitate M2M communication. The second is broad availability of flexible, cost-effective storage designed to handle the massive surge in back-end data in a world where timely analytics is e...
SYS-CON Events announced today that Akana, formerly SOA Software, has been named “Bronze Sponsor” of SYS-CON's 16th International Cloud Expo® New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. Akana’s comprehensive suite of API Management, API Security, Integrated SOA Governance, and Cloud Integration solutions helps businesses accelerate digital transformation by securely extending their reach across multiple channels – mobile, cloud and Internet of Things. Akana enables enterprises to share data as APIs, connect and integrate applications, drive part...