Welcome!

Java IoT Authors: Liz McMillan, Pat Romanski, Elizabeth White, Stackify Blog, Mamoon Yunus

Related Topics: Machine Learning , Java IoT

Machine Learning : Article

Meet AJAX: 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 specific 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" dependency 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>

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 (8) 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
SYS-CON India News Desk 02/19/06 07:05:30 PM EST

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.

Anatole Tartakovsky 12/26/05 06:15:32 PM EST

I received number of questions on the future of the AJAX recently - tried to give my personal view on the possible development in the blog - http://anatolet.blogspot.com

Frank 12/19/05 07:04:50 PM EST

You mention the need to destroy the request and callback objects, but my O'Reilly reference says there is no need to clean up in javascript. Which is correct.

How do you destroy the request and especially the callback objects (can I destroy the callback in the callback!!!)?

Halans 10/15/05 06:25:27 PM EDT

Nice, to the point, Ajax article.
Though some comments (nitpicking)... Wasn't the term 'Ajax' introduced in the Adaptive Path article from february 2005, not march 2004?
You add style attributes with values 'width:30', but you should add 'px' ('width:30px') to make it standards compliant and make firefox display it correctly (IE is way too lax).
Wouldn't you best upon readyState==4 also check the http status 200 before continuing?
You should best add an existing default url to the iframe (ex 'blank.html'), because when you would do this over https (without a url to begin with) you would get an ugly security message in IE, making you pull your hair out to solve this (I lost a bunch one time).
While you did the iframe example, you might have integrated it with the xmlhttprequest for gracefull degradation in an (corporate) IE environment with ActiveX disabled, no?
But like I said, nitpicking.
Looking forward for the upcoming Ajax articles.

Victor Rasputnis 10/04/05 08:04:22 AM EDT

Anand, you are right. The example was meant to be the most obvious, to avoid problems with getRealPath() or explanation around getResourseAsStream() etc. You have a good eye :), thanks again.

Anand 10/03/05 01:42:54 PM EDT

Thanks Victor. I had figured out application instead of using getServletContext() on BEA. However my problem was with the

properties.load(new java.io.FileInputStream(key + ".property"));

I had the file in the same folder and thought that I did not need to provide it with an explicit path such as c:\\ but I guess that is not the case. Also one more change to the html file that I figured in the line:
zip.length = 3 ? updateState(zip) : zip.length == 5 ? updateCity(zip):"";

should be

zip.length == 3 ? updateState(zip) : zip.length == 5 ? updateCity(zip):"";

Victor Rasputnis 09/30/05 10:31:34 PM EDT

Anand, getServletContext() is available in Tomcat JSP, but not in WebLogic (WL -getServletConfig().getServletContext()). Anyway, I replaced gSC() to _application_ for simplicity. Please download again. Most importantly, please also download the DATA files or ZIP will remain red, no matter what :).

Kind Regards,
Victor Rasputnis

Anand 09/29/05 08:42:16 AM EDT

I tried doing this sample using both IE 6 and Firefox. Everytime I type in 3 digits (valid zip code) it paints the box red. It does not populate the city and state. Using BEA I got an error on the JSP page saying that getServletContext() was not recognized. On Tomcat I did not get any error but the program won't work.
Any suggestions ?

@ThingsExpo Stories
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
SYS-CON Events announced today that Dasher Technologies will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Dasher Technologies, Inc. ® is a premier IT solution provider that delivers expert technical resources along with trusted account executives to architect and deliver complete IT solutions and services to help our clients execute their goals, plans and objectives. Since 1999, we'v...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infrastructure thro...
SYS-CON Events announced today that Grape Up will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company specializing in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market across the U.S. and Europe, Grape Up works with a variety of customers from emergi...
SYS-CON Events announced today that Elastifile will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Elastifile Cloud File System (ECFS) is software-defined data infrastructure designed for seamless and efficient management of dynamic workloads across heterogeneous environments. Elastifile provides the architecture needed to optimize your hybrid cloud environment, by facilitating efficient...
SYS-CON Events announced today that Grape Up will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company specializing in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market across the U.S. and Europe, Grape Up works with a variety of customers from emergi...
SYS-CON Events announced today that Golden Gate University will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Since 1901, non-profit Golden Gate University (GGU) has been helping adults achieve their professional goals by providing high quality, practice-based undergraduate and graduate educational programs in law, taxation, business and related professions. Many of its courses are taug...
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...
21st International Cloud Expo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Me...
Recently, WebRTC has a lot of eyes from market. The use cases of WebRTC are expanding - video chat, online education, online health care etc. Not only for human-to-human communication, but also IoT use cases such as machine to human use cases can be seen recently. One of the typical use-case is remote camera monitoring. With WebRTC, people can have interoperability and flexibility for deploying monitoring service. However, the benefit of WebRTC for IoT is not only its convenience and interopera...
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...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, will introduce two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a...
SYS-CON Events announced today that Secure Channels, a cybersecurity firm, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Secure Channels, Inc. offers several products and solutions to its many clients, helping them protect critical data from being compromised and access to computer networks from the unauthorized. The company develops comprehensive data encryption security strategie...
SYS-CON Events announced today that App2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. App2Cloud is an online Platform, specializing in migrating legacy applications to any Cloud Providers (AWS, Azure, Google Cloud).
WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web communications world. The 6th WebRTC Summit continues our tradition of delivering the latest and greatest presentations within the world of WebRTC. Topics include voice calling, video chat, P2P file sharing, and use cases that have already leveraged the power and convenience of WebRTC.
Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, shared examples from a wide range of industries – including en...
Detecting internal user threats in the Big Data eco-system is challenging and cumbersome. Many organizations monitor internal usage of the Big Data eco-system using a set of alerts. This is not a scalable process given the increase in the number of alerts with the accelerating growth in data volume and user base. Organizations are increasingly leveraging machine learning to monitor only those data elements that are sensitive and critical, autonomously establish monitoring policies, and to detect...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. Jack Norris reviews best practices to show how companies develop, deploy, and dynamically update these applications and how this data-first...
Intelligent Automation is now one of the key business imperatives for CIOs and CISOs impacting all areas of business today. In his session at 21st Cloud Expo, Brian Boeggeman, VP Alliances & Partnerships at Ayehu, will talk about how business value is created and delivered through intelligent automation to today’s enterprises. The open ecosystem platform approach toward Intelligent Automation that Ayehu delivers to the market is core to enabling the creation of the self-driving enterprise.