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

ColdFusion: Article

Facing the Challenges Part 2

Facing the Challenges Part 2

It's fun developing wireless applications in ColdFusion, but if you don't solve several key challenges it'll be more painful than pleasant.

In this second part of a series, I'll focus on some common problems encountered by CF/WML developers.

In the last issue the focus was on getting you started: an introduction to WAP (the Wireless Access Protocol), the early state of wireless programming, how to get a simulator to begin testing code, resources for learning more about WAP and the markup language for WAP phones, WML (Wireless Markup Language).

I intentionally didn't focus on WML itself or on the details of the WAP architecture. These matters are best left to the many SDK documents, Web sites and the growing number of books on the subject.

In this issue I'll focus on matters not covered by those resources: the problems you'll typically encounter when getting started with wireless programming in conjunction with ColdFusion. There are indeed many challenges that would affect any WML developer. I'll touch on a couple of them, but the real focus is on the CF-specific challenges, as well as some tips and tricks for getting things to work when trouble strikes.

The Key to Doing WML in CF
Before discussing the common challenges, I ought to at least give you a bit of sample code to begin with in case this is your first time reading about WML. As mentioned in the last article, I don't want to repeat too much of what was covered by Ben Forta's intro to WML in his December 1999 article, "No Strings Attached" (Vol. 1, issue 6). Please see that for more introductory WML.

The bottom line is that all you need is a properly formatted CFCONTENT tag to indicate to the browser that the code you're building is WML rather than HTML (ColdFusion's default). This sets the MIME type of the page you're creating. Simply include this at the top of your program:

<CFCONTENT TYPE="text/vnd.wap.wml">
That's not quite all you need. There's a set of basic "prologue" statements that must be specified at the top of any WML page, so the more complete definition of the beginning of a CF/WML page, as offered in a simple "Hello World" example, is:
<CFCONTENT TYPE="text/vnd.wap.wml"><?xml version="1.0"?>
<!DOCTYPE wml PUBLIC"-//WAPFORUM//DTD WML 1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml">
<wml>
<card>
<p>
Hello World
</p>
</card>
</wml>
Notice that we've put the first two lines of code on the same line. Many WML developers have found that the ?xml declaration line should be coded without any carriage returns preceding it.

From here you can use any CF code to generate any WML as needed by your application. Again, see other more general-interest WML resources for more about the WML you can use. And you can do this in any version of CF. This leads to a natural question often asked by new CF/WML developers: What version of ColdFusion allows WML programming?

When people notice that Allaire has highlighted new WML support in 4.5, they get the impression that WML can only be done in 4.5 of CF Server. In fact, the new support is really just extensions to CF Studio and HomeSite to support creating, editing and getting help on WML tags, and a new page wizard. We'll review those in a later article.

Any version of ColdFusion (Server and Studio) can support WML programming if you're coding the tags by hand, since all you need is that CFCONTENT tag at the top of the page.

The Inevitable Errors You'll Encounter
If you try this sample code, or when you begin doing more substantial code, you'll inevitably encounter errors. The challenge is determining if it's a CF error or a WML error, and even then what works in one phone may fail in another due to the incompatibilities of phones supporting WML in different ways (which is beyond the scope of this article). But there are some simple issues we can deal with.

Viewing the Code in the Right Browser
First of all, you can't expect to run the preceding code sample from within a browser like IE or Netscape (at least not the current versions). With the CFCONTENT tag in place, you can view the output of the page only in a browser that supports WML (phones or phone simulators, as discussed in the last article). If you try to view it in a normal browser, you'll likely receive a prompt to save the file being sent, since the browser doesn't know what to do with a file of the MIME type specified in the CFCONTENT tag.

Dealing with "Invalid Content" or "Syntax Errors"
Even when viewed on a real phone (or simulator), you'll encounter errors in your first forays into WML. There are a few things to keep in mind.

First, WML is case-sensitive. You must use lowercase for WML tags and attributes. Also, WML follows the rules of XML programming, so all tags must have a closing tag. Even a <p> tag must have a closing </p>, unlike in HTML, and tags like <br>, which have no closing tag, must be written as <br/>.

Note that you can't send HTML tags to a WML browser. (Well, that's not entirely true. Some WAP gateways can convert HTML to WML, but that's not universal and shouldn't be relied on.) If you send HTML to WML browsers, they'll generally "choke" on it. So be careful – don't intermix HTML and WML. You really need to find some WML resources to learn more. For all their similarity, there are many significant differences between HTML and WML programming, and they're more than just differences in tag names.

Other problems could arise if you have an error in your CF code (causing CF to display an error message), or if you have server-side debugging information turned on, both of which generate HTML, as we'll discuss next.

Turn Off Server-Side Debugging
ColdFusion's HTML heritage can really get in the way when doing WML programming. When debugging is turned on in the Administrator, you normally see the debugging info at the bottom of any CF page. But that information is sent in HTML formatting to the browser, which is fine in a normal browser, but it's death to most WML browsers since they can't read HTML.

You don't need to turn off debugging in the Administrator. As of ColdFusion release 4, you have the option to turn off debugging with the following line of code:

<CFSETTING SHOWDEBUGOUTPUT="no">
This will disable debugging until you turn it on again or until the currently running template ends. If you're running a release of ColdFusion prior to release 4, it's probably best to just turn off server-side debugging.

Why Can't I See ColdFusion Error Messages?
On a related matter, the same problem of CF's HTML heritage has to do with error message handling. When you get an error in CF, you normally see the CF error message display indicating the error and the page and line number of the code in error. But that error is also sent in HTML formatting to the browser, which chokes the WML browser.

This would seem a real dilemma. You can't see the error because the phone doesn't recognize it as valid WML. So how are you supposed to deal with it? Well, fortunately, Allaire has put in place error-handling components to improve the ability of the developer to control the error message display to the user.

You might think that CFERROR, and its ability to create a specially formatted error page, might come to the rescue. Unfortunately, the two older forms of CFERROR pages (type="request" and type="validation") send pure HTML (and an HTML MIME type), which you can't override. Since you can't put any CF tags on those error pages, you can't even add a CFCONTENT.

(This also means, of course, that you can't use CF's hidden field validation to do server-side form validation. The validation error page that it offers is also pure HTML and you can't override it.)

Perhaps Allaire will offer a solution to these dilemmas in the future. For now, if you have release 4.5, you can in many cases at least solve some of the first problem – seeing CF error messages – by taking advantage of the new CFERROR type="exception". This transfers control when an error occurs to a page that is allowed to do CF tags (an incredibly valuable new feature in and of itself), including a CFCONTENT tag. You can then format the error for display to the WML browser.

Formatting the Error Message Itself
You're not quite done, though. The CF error message itself, offered inside such a CFERROR page as the variable CFERROR.Diagnostics, will usually be HTML-formatted. This was fine when sending it for display to an HTML browser, but again it's a problem in WML. Fortunately, you can solve it by using a CF function to convert the HTML tags in the message into their corresponding display codes, such as &gt; for > and &lt; for <.

Allaire offers two solutions for this. In 4.5 there's an XmlFormat() function for just this purpose. In older releases you can use HtmlEditFormat(). It's not the perfect solution, as it'll simply cause any HTML tags in the error message to be displayed to the screen, but it's easier than trying to strip out the HTML tags.

This approach can also be used to format error messages displayed in a CFCATCH (using the "cfcatch.detail" variable).

You may want to create an application.cfm that sets the CFSETTING to disable debugging output (on a release 4 or above server) and sets a CFERROR type="exception" (on a release 4.5 or above server) to point to a template that can format the error message in WML.

Keep in mind that none of this CF error handling will help if the error in your page is due to badly formed WML. In this case you'd do well to have a simulator that allows you to see the actual WML being sent to the browser (most real phones won't provide access to that information).

Form Processing Works in Simulator, Fails in Real Phone
This is another thorny problem, and it's not generally CF-specific. Some background will help. When you test code in most simulators, you may be using a form of communication between the simulator and the Web server that's often called "http direct". There is direct communication between the simulator and the server.

This is fine, but real phones use a form of communication that goes from the phone to a gateway (usually within the phone company provider) that then communicates to the Web server on the phone user's behalf. (It acts as both a proxy and a translator, since what's really sent to real phones is an encoded form of WML to minimize data traffic.)

The problem with this scenario is that code that works fine in the "http direct" mode may fail when run on a real phone or in the simulator's gateway mode.

A perfect example of this is "form processing" by way of the "post" method. If the example in Listing 1 is submitted on a simulator, it will work, but on a real phone it may fail.

I don't have room here to explain the unique differences of form processing in WML versus HTML, but the example shows many of the significant features. Note that there's no "form" tag per se, and that the form data is gathered in one place (the input tag), stored in a variable on the phone ("stock") and passed to the server in yet another tag (<go>) when the user presses the "accept" button or equivalent. Very different from HTML! But note the powerful new formatting possibilities in the <input> tag. This allows only up to four alphanumeric characters.

The problem occurs when the page itself is submitted with method="post". In testing on a simulator in HTTP direct mode, this code works fine. In a real phone, however, which goes through a gateway, it will fail to submit. In the Phone.com simulator, using the "up.link" mode to go through a gateway, it fails with an error "500:internal server error". It seems the gateway is simply unable to make a "post" method call to the server.

And it doesn't seem to be restricted to CF Server (I tested the problem against an ASP program and got the same error). It may be restricted to Phone.com gateways, though I've heard it happened to users of Nokia phones and simulators.

The short-term solution is to change the method to "get". ColdFusion will receive the variables as "url." variables (in the example above, the "url.symbol"). Unlike in HTML browsers, this doesn't have the same problem of showing the user the form variables on the URL of the action page since phone users don't see the URLs of sites they're visiting (currently).

There is the security risk that on an SSL-enabled connection (called WTLS in the WAP world) the data passed on the URL isn't encrypted, so this isn't a solution that will work when passing userids and passwords, or credit cards if the goal is to encrypt that data. But that, too, is beyond the scope of this article.

That's All for Now
That's all the time (or rather, room) we have this month. Upcoming articles in this series will cover some other challenges (and solutions) regarding wireless development, such as doing browser detection to serve both HTML and WML browsers, handling sessions in an environment in which cookies aren't always supported, doing CFLOCATION (you have to use Web server root-relative paths, even to send to a file in the same directory), what to do when CFCONTENT simply doesn't work in your CF server, processing multivalued form field submissions, sending notifications and pushing messages to the phone (using COM objects), and the support in Studio for WML.

You can learn about WML and generic challenges as well as more about these CF challenges in the recently released book Professional WAP (Wrox Press). I have a chapter in the book on CF/WML programming. Other WML/WAP books will soon be in the market as well.

More Stories By Charlie Arehart

A veteran ColdFusion developer since 1997, Charlie Arehart is a long-time contributor to the community and a recognized Adobe Community Expert. He's a certified Advanced CF Developer and Instructor for CF 4/5/6/7 and served as tech editor of CFDJ until 2003. Now an independent contractor (carehart.org) living in Alpharetta, GA, Charlie provides high-level troubleshooting/tuning assistance and training/mentoring for CF teams. He helps run the Online ColdFusion Meetup (coldfusionmeetup.com, an online CF user group), is a contributor to the CF8 WACK books by Ben Forta, and is frequently invited to speak at developer conferences and user groups worldwide.

Comments (0)

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.


@ThingsExpo Stories
The Internet of Everything (IoE) brings together people, process, data and things to make networked connections more relevant and valuable than ever before – transforming information into knowledge and knowledge into wisdom. IoE creates new capabilities, richer experiences, and unprecedented opportunities to improve business and government operations, decision making and mission support capabilities.
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists addressed this very serious issue of profound change in the industry.
Discussions about cloud computing are evolving into discussions about enterprise IT in general. As enterprises increasingly migrate toward their own unique clouds, new issues such as the use of containers and microservices emerge to keep things interesting. In this Power Panel at 16th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the state of cloud computing today, and what enterprise IT professionals need to know about how the latest topics and trends affect their organization.
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
For IoT to grow as quickly as analyst firms’ project, a lot is going to fall on developers to quickly bring applications to market. But the lack of a standard development platform threatens to slow growth and make application development more time consuming and costly, much like we’ve seen in the mobile space. In his session at @ThingsExpo, Mike Weiner, Product Manager of the Omega DevCloud with KORE Telematics Inc., discussed the evolving requirements for developers as IoT matures and conducted a live demonstration of how quickly application development can happen when the need to comply wit...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world and it starts with business models and monetization strategies.
Converging digital disruptions is creating a major sea change - Cisco calls this the Internet of Everything (IoE). IoE is the network connection of People, Process, Data and Things, fueled by Cloud, Mobile, Social, Analytics and Security, and it represents a $19Trillion value-at-stake over the next 10 years. In her keynote at @ThingsExpo, Manjula Talreja, VP of Cisco Consulting Services, discussed IoE and the enormous opportunities it provides to public and private firms alike. She will share what businesses must do to thrive in the IoE economy, citing examples from several industry sectors.
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Opening Keynote at 16th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, d...
There will be 150 billion connected devices by 2020. New digital businesses have already disrupted value chains across every industry. APIs are at the center of the digital business. You need to understand what assets you have that can be exposed digitally, what their digital value chain is, and how to create an effective business model around that value chain to compete in this economy. No enterprise can be complacent and not engage in the digital economy. Learn how to be the disruptor and not the disruptee.
Akana has released Envision, an enhanced API analytics platform that helps enterprises mine critical insights across their digital eco-systems, understand their customers and partners and offer value-added personalized services. “In today’s digital economy, data-driven insights are proving to be a key differentiator for businesses. Understanding the data that is being tunneled through their APIs and how it can be used to optimize their business and operations is of paramount importance,” said Alistair Farquharson, CTO of Akana.
Business as usual for IT is evolving into a "Make or Buy" decision on a service-by-service conversation with input from the LOBs. How does your organization move forward with cloud? In his general session at 16th Cloud Expo, Paul Maravei, Regional Sales Manager, Hybrid Cloud and Managed Services at Cisco, discusses how Cisco and its partners offer a market-leading portfolio and ecosystem of cloud infrastructure and application services that allow you to uniquely and securely combine cloud business applications and services across multiple cloud delivery models.
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, analyzed how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI Intelligence, he worked analyzing bank technology for Corporate Insight and The Clearing House Payment...
In his keynote at 16th Cloud Expo, Rodney Rogers, CEO of Virtustream, discussed the evolution of the company from inception to its recent acquisition by EMC – including personal insights, lessons learned (and some WTF moments) along the way. Learn how Virtustream’s unique approach of combining the economics and elasticity of the consumer cloud model with proper performance, application automation and security into a platform became a breakout success with enterprise customers and a natural fit for the EMC Federation.
"Optimal Design is a technology integration and product development firm that specializes in connecting devices to the cloud," stated Joe Wascow, Co-Founder & CMO of Optimal Design, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
SYS-CON Events announced today that CommVault has been named “Bronze Sponsor” of SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. A singular vision – a belief in a better way to address current and future data management needs – guides CommVault in the development of Singular Information Management® solutions for high-performance data protection, universal availability and simplified management of data on complex storage networks. CommVault's exclusive single-platform architecture gives companies unp...
Electric Cloud and Arynga have announced a product integration partnership that will bring Continuous Delivery solutions to the automotive Internet-of-Things (IoT) market. The joint solution will help automotive manufacturers, OEMs and system integrators adopt DevOps automation and Continuous Delivery practices that reduce software build and release cycle times within the complex and specific parameters of embedded and IoT software systems.
"ciqada is a combined platform of hardware modules and server products that lets people take their existing devices or new devices and lets them be accessible over the Internet for their users," noted Geoff Engelstein of ciqada, a division of Mars International, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Internet of Things is moving from being a hype to a reality. Experts estimate that internet connected cars will grow to 152 million, while over 100 million internet connected wireless light bulbs and lamps will be operational by 2020. These and many other intriguing statistics highlight the importance of Internet powered devices and how market penetration is going to multiply many times over in the next few years.
SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.