Welcome!

Machine Learning Authors: Ed Featherston, Elizabeth White, Dan Blacharski, Liz McMillan, William Schmarzo

Related Topics: Machine Learning

Machine Learning : Article

Intelligent Web Applications with AJAX

A peek into modern technologies for browser-based applications

Browser-based applications are widely used and we like the fact that we can access them from anywhere. But from the users' perspective, the productivity level of Web applications still doesn't approximate the productivity of desktop programs. The good news is the gap is closing: the accumulated potential of multiple technologies has boosted a whole new breed of HTML-based apps that are as powerful as the desktop ones. Meet AJAX.

What Is AJAX?
The name stands for Asynchronous JavaScript + XMLHTTPRequest and means you can establish socket communication between browser-based JavaScript and the server. AJAX isn't a new technology. It's a successful branding of possibilities implanted in several technologies available in modern browsers. All AJAX applications deliver a rich UI via extensive JavaScript manipulation of the HTML Document Object Model based on the precision-pointed data retrieval via XMLHttpRequest. Typical examples of AJAX applications are Google Maps and Google Suggest from Google Labs (http://labs.google.com). These applications actively monitor user input and provide real-time page updates. Most importantly, this happens without a page refresh while the user navigates through the map or types a search string.

In fact, the technologies behind these wonders have been around for a while, although they require sophisticated skills in using browser-specific tricks. Proprietary offerings with similar capabilities - Macromedia Flash plug-in, Java Applets or .NET runtime - have been available for quite some time too. The idea of integrating a scriptable transport component talking to the server into the browser was pioneered by IE 5.0. Then Firefox and other popular browsers joined the club of browsers in supporting XMLHTTPRequest as a built-in object. With cross-browser availability, these technologies gained visibility and in March of 2004 a company called Adaptive Path introduced AJAX.

In short, backing from Google and having the right browser technologies available out-of-the-box tipped the scale: these days everyone is adding client-side technologies to Web applications for a "better user experience."

AJAX vs. Classical Applications
A classic Web application model is literally a triumph of form over substance: users are forced to submit forms in exchange for pages. That said, the form submission and page delivery aren't guaranteed: worse case the user clicks again though some pages specifically warn against that. It's quite different with AJAX, where the data travels across the wire instead of entire HTML pages. This data exchange is scripted via a specific browser object - XMLHttpRequest; the appropriate logic handles the outcome of each data request, the specifc region of the page is updated instead of the entire page. The results are more speed, less traffic, and better control of information delivery.

Traditional "click-refresh" Web applications force users to interrupt the work process while waiting for the page to reload. With AJAX, a client-side script can asynchronously talk to the server while the user keeps entering data. Besides being transparent to the user, such asynchrony means more time for the server to process the request.

Classic Web applications delegate all processing to the server and force the server to manage the state. AJAX allows flexible partitioning of the application logic and state management between the client and the server. This eliminates a "click-refresh" dependancy and provides better server scalability. When the state is stored on the client-side you don't have to maintain sessions across the servers or save/expire state: the lifespan is defined by client.

AJAX: Distributed MVC
Although AJAX applications rely on JavaScript for the presentation layer, the processing power and knowledge base remain on the server. For that matter, AJAX applications talk heavily to J2EE servers, feeding data to and from Web Services and servlets. The difference between J2EE applications with an AJAX-based presentation tier and standard J2EE application is that in the first case MVC is distributed over the wire. With AJAX, View is local, while Model and Controller are distributed giving the developer the flexibility to decide which components will be client-based. Specifically, a local View renders graphics by manipulating with HTML DOM; the controller handles user input locally and at the developer's discretion extends the processing to the server via HTTP requests (Web Services, XML/RPC or others); the remote part of the Model is downloaded as needed to the client achieving in-place real-time updates of the client page; and state is collected on the client.

In future AJAX articles we'll talk about each of these components in depth and provide examples of how they came to play together. Now, without further ado, let's dive into a simple AJAX example.

Zip Codes Validation and Lookup
We'll create an HTML page containing three INPUT fields: Zip, City, and State. We'll make sure that as soon as the user enters the first three digits of the zip code, the state will get populated with the first matching state value. Once the user types in all five zip digits, we'll instantly determine and populate the appropriate city. If the zip code isn't valid (not found in the server's database), we'll turn the zip's border color to red. Such visual clues are helpful to users and have become standard in modern browsers (as an example, Firefox finds matching words in an HTML page by highlighting them in the browser search field while you type).

Let's start with a simple HTML containing three input fields: zip, city, and state. Please note that the method zipChanged() is called as soon as a character is entered in the zip field. In turn, the JavaScript function zipChanged() (see below) calls the function updateState() when the zip length is three and up-dateCity() when the length of the zip is five. Both updateCity() and updateState() delegate most of the work to another function - ask().

Zip:<input id="zipcode" type="text" maxlength="5" onKeyUp="zipChanged()" style="width:60"/>
City: <input id="city" disabled maxlength="32" style="width:160"/>
State:<input id="state" disabled maxlength="2" style="width:30"/>

<script src="xmlhttp.js"></script>
<script>
var zipField = null;
function zipChanged(){
    zipField = document.getElementById("zipcode")
    var zip = zipField.value;
    zip.length == 3?updateState(zip):zip.length == 5?updateCity(zip):"";

}
function updateState(zip) {
    var stateField = document.getElementById("state");
    ask("resolveZip.jsp?lookupType=state&zip="+zip, stateField, zipField);
}
function updateCity(zip) {
    var cityField = document.getElementById("city");
    ask("resolveZip.jsp? lookupType=city&zip="+zip, cityField, zipField);
}
</script>

The function ask() communicates with the server and assigns a callback to process the server's response (see the following code). Later, we'll look at the content of the dual-natured resolveZip.jsp that looks up the city or state information depending on the number of characters in the zip field. Importantly, ask() uses the asynchronous flavor of the XmlHttpRequest so that populating the state and city fields or coloring the zip border is done without slowing data entry down. First, we call request.open(), which opens the socket channel with the server using one of the HTTP verbs (GET or POST) as the first argument and the URL of the data provider as a second one. The last argument of the request.open() is set to true, which indicates the asynchronous nature of the request. Note that the request hasn't been submitted yet. That happens with the request.send() call, which can provide any necessary payload for POST. With asynchronous requests we have to assign the request's callback using the request.onreadystatechanged attribute. (If the request had been synchronous, we could have processed the results immediately after request.send, but we would have blocked the user until the request was completed.)

HTTPRequest = function () {
   var xmlhttp=null;
   try {
     xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
   } catch (_e) {
     try {
       xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
     } catch (_E) { }
   }
   if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
     try {
       xmlhttp = new XMLHttpRequest();
     } catch (e) {
       xmlhttp = false;
   } }
   return xmlhttp;
}

function ask(url, fieldToFill, lookupField) {
    var http = new HTTPRequest();
    http.open("GET", url, true);
    http.onreadystatechange = function (){ handleHttpResponse(http, fieldToFill, lookupField)};
    http.send(null);
}

function handleHttpResponse(http, fieldToFill, lookupField) {
   if (http.readyState == 4) {
     result = http.responseText;
     if ( -1 != result.search("null") ) {
       lookupField.style.borderColor = "red";
       fieldToFill.value = "";
     } else {
       lookupField.style.borderColor = "";
       fieldToFill.value = result;
} } }

The HttpRequest() function (see above) used by ask() is a cross-browser constructor of an instance of the XMLHTTPRequest; we'll look at it a bit later. For now, note how the invocation of handleResponse() is wrapped by an anonymous function (a so-called closure) function (){ handleHttpResponse(http, fieldToFill, lookupField)}.

The code for that function is dynamically created and compiled every time we do an assignment to the http.onreadstatechange property. As a result, JavaScript creates a pointer to the context with all variables that the enclosing method - ask() - has access to. It's done so the anonymous function and handleResponse() are guaranteed full access to all context-hosted variables until the reference to the anonymous function is garbage-collected. In other words, whenever our anonymous function gets invoked, it can refer to the request, fieldToFill, and lookupField variables as seamlessly as if they were global. It's also true that every invocation of ask() will create a separate copy of the environment with the variables holding the values of the moment the closure was formed.


More Stories By Victor Rasputnis

Dr. Victor Rasputnis is a Managing Principal of Farata Systems. He's responsible for providing architectural design, implementation management and mentoring to companies migrating to XML Internet technologies. He holds a PhD in computer science from the Moscow Institute of Robotics. You can reach him at [email protected]

More Stories By Anatole Tartakovsky

Anatole Tartakovsky is a Managing Principal of Farata Systems. He's responsible for creation of frameworks and reusable components. Anatole authored number of books and articles on AJAX, XML, Internet and client-server technologies. He holds an MS in mathematics. You can reach him at [email protected]

More Stories By Igor Nys

Igor Nys is a Director of Technology Solutions at EPAM Systems, Inc, a company combining IT consulting expertise with advanced onshore-offshore software development practices. Igor has been working on many different computer platforms and languages including Java, C++, PowerBuilder, Lisp, Assembler since the mid 80's. Igor is currently managing a number of large distributed projects between US and Europe. In addition Igor is the author of the award-winning freeware system-management tools, and he was closely involved in the development of XMLSP technology - one of the AJAX pioneers.

Comments (2)

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.


@CloudExpo Stories
The need for greater agility and scalability necessitated the digital transformation in the form of following equation: monolithic to microservices to serverless architecture (FaaS). To keep up with the cut-throat competition, the organisations need to update their technology stack to make software development their differentiating factor. Thus microservices architecture emerged as a potential method to provide development teams with greater flexibility and other advantages, such as the abili...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settle...
Product connectivity goes hand and hand these days with increased use of personal data. New IoT devices are becoming more personalized than ever before. In his session at 22nd Cloud Expo | DXWorld Expo, Nicolas Fierro, CEO of MIMIR Blockchain Solutions, will discuss how in order to protect your data and privacy, IoT applications need to embrace Blockchain technology for a new level of product security never before seen - or needed.
The cloud era has reached the stage where it is no longer a question of whether a company should migrate, but when. Enterprises have embraced the outsourcing of where their various applications are stored and who manages them, saving significant investment along the way. Plus, the cloud has become a defining competitive edge. Companies that fail to successfully adapt risk failure. The media, of course, continues to extol the virtues of the cloud, including how easy it is to get there. Migrating...
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
The use of containers by developers -- and now increasingly IT operators -- has grown from infatuation to deep and abiding love. But as with any long-term affair, the honeymoon soon leads to needing to live well together ... and maybe even getting some relationship help along the way. And so it goes with container orchestration and automation solutions, which are rapidly emerging as the means to maintain the bliss between rapid container adoption and broad container use among multiple cloud host...
Blockchain is a shared, secure record of exchange that establishes trust, accountability and transparency across business networks. Supported by the Linux Foundation's open source, open-standards based Hyperledger Project, Blockchain has the potential to improve regulatory compliance, reduce cost as well as advance trade. Are you curious about how Blockchain is built for business? In her session at 21st Cloud Expo, René Bostic, Technical VP of the IBM Cloud Unit in North America, discussed the b...
Blockchain. A day doesn’t seem to go by without seeing articles and discussions about the technology. According to PwC executive Seamus Cushley, approximately $1.4B has been invested in blockchain just last year. In Gartner’s recent hype cycle for emerging technologies, blockchain is approaching the peak. It is considered by Gartner as one of the ‘Key platform-enabling technologies to track.’ While there is a lot of ‘hype vs reality’ discussions going on, there is no arguing that blockchain is b...
Imagine if you will, a retail floor so densely packed with sensors that they can pick up the movements of insects scurrying across a store aisle. Or a component of a piece of factory equipment so well-instrumented that its digital twin provides resolution down to the micrometer.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
As DevOps methodologies expand their reach across the enterprise, organizations face the daunting challenge of adapting related cloud strategies to ensure optimal alignment, from managing complexity to ensuring proper governance. How can culture, automation, legacy apps and even budget be reexamined to enable this ongoing shift within the modern software factory? In her Day 2 Keynote at @DevOpsSummit at 21st Cloud Expo, Aruna Ravichandran, VP, DevOps Solutions Marketing, CA Technologies, was jo...
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, discussed how data centers of the future will be managed, how the p...
"Since we launched LinuxONE we learned a lot from our customers. More than anything what they responded to were some very unique security capabilities that we have," explained Mark Figley, Director of LinuxONE Offerings at IBM, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
In his general session at 21st Cloud Expo, Greg Dumas, Calligo’s Vice President and G.M. of US operations, discussed the new Global Data Protection Regulation and how Calligo can help business stay compliant in digitally globalized world. Greg Dumas is Calligo's Vice President and G.M. of US operations. Calligo is an established service provider that provides an innovative platform for trusted cloud solutions. Calligo’s customers are typically most concerned about GDPR compliance, application p...
You know you need the cloud, but you’re hesitant to simply dump everything at Amazon since you know that not all workloads are suitable for cloud. You know that you want the kind of ease of use and scalability that you get with public cloud, but your applications are architected in a way that makes the public cloud a non-starter. You’re looking at private cloud solutions based on hyperconverged infrastructure, but you’re concerned with the limits inherent in those technologies.
Is advanced scheduling in Kubernetes achievable?Yes, however, how do you properly accommodate every real-life scenario that a Kubernetes user might encounter? How do you leverage advanced scheduling techniques to shape and describe each scenario in easy-to-use rules and configurations? In his session at @DevOpsSummit at 21st Cloud Expo, Oleg Chunikhin, CTO at Kublr, answered these questions and demonstrated techniques for implementing advanced scheduling. For example, using spot instances and co...