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

Expect The Unexpected

Expect The Unexpected

No one wants to write buggy code, at least no one I choose to know. Bugs are annoying, bugs are embarrassing. And bugs can cost you (and your clients) lots of time and money.

Bugfree code is the ideal all developers strive for - at least should strive for - but it's a lofty goal not easily attained.

To write bugfree code it's important to understand how bugs are introduced. I'd like to explore what I believe to be one of the primary causes for the introduction of bugs into your code: failure to expect the unexpected. While many of these ideas apply to application development in general, the positioning of this column relates specifically to ColdFusion.

Flow? What Flow?
Applications are designed with a particular program flow in mind. Users start at point A, go to point B, then to point C. Program flow is an important part of any application, and when developers write they anticipate a particular program flow.

Here are some examples.

  • A search dialog is displayed, the user enters search criteria, a search is performed and the results are displayed.

  • The user browses a product catalog, makes multiple selections with possible confirmations and provides payment information, after which the order is saved and processed.

  • A login screen is displayed and the user provides authentication information, which is validated against a database. If authenticated, access is granted; otherwise the login screen is redisplayed.

    In each of these examples there's a logical starting point, then a series of steps. The search dialog must be displayed before the search can be performed, users must select items from the product catalog before the order can be processed, and login information must be provided before access can be authenticated.

    In traditional application development, programmers had total control over program flow. Users had no way to access screens out of order, nor could they start from a screen other than the one they were supposed to start at. But Web applications, for better or worse, behave differently. As every Web page has a unique address (its URL), it's indeed possible for users to execute pages out of order, just as it's possible for them to start from the wrong page.

    How could this occur? There are several ways. Users could bookmark pages directly, search engines might index pages below your root, and newer browsers feature an auto-fill option that completes URLs for users but frequently uses the most recently visited page in the site (often the wrong page).

    To understand this better, look at the following code:

    <!--- Perform search --->
    <CFQUERY DATASOURCE="ds" NAME="search">
    SELECT title FROM books
    WHERE title LIKE %#FORM.title#%'
    </CFQUERY>
    <!--- Create page --->
    <HTML>
    <BODY>
    <H1>Search Results</H1>
    <UL>
    <!--- Display search results --->
    <CFOUTPUT QUERY="search">
    <LI>#title#
    </CFOUTPUT>
    </UL>
    </BODY>
    </HTML>

    What's wrong with the above code?

    Actually, this is fairly typical ColdFusion code (it's even commented). It performs a simple database search and displays the results. The search itself is driven by a form that contains a field named "title"

    And that's what's wrong. The code makes two dangerous assumptions - that the page will be called from a form and that the form contains a field named "title". If either assumption turns out to be incorrect, ColdFusion throws an error because #FORM.title# would refer to a variable that didn't exist.

    What's the solution? There are a couple of things you can and should do. The first is always check for the existence of variables before using them, initializing them with default values if needed. The ColdFusion <CFPARAM> tag is very useful for this, and good programming practices demand that every variable be initialized this way so they always exist (either as submitted FORM or URL values, or as locally created variables). If the following code were inserted above the code example, the page would always execute correctly, regardless of how it was invoked and what fields were passed:

    <CFPARAM NAME="FORM.title" DEFAULT="">

    Sometimes you may not want to use default values. For example, in the preceding code you may not want to display the entire contents of the table if the page is executed directly. If a user ends up on this page without having filled in the form to perform the search, you'd want to send them to the search page instead. Here's one way you could do this (assuming the search page was named search.cfm):

    <!--- Is form field present? --->
    <CFIF NOT IsDefined("FORM.title")>
    <!--- Not present, redirect to search screen --->
    <CFLOCATION URL="search.cfm">
    </CFIF>

    With this snippet at the top of the page your code is now safe. If users try to execute the page directly, you'll programmatically redirect them to where they really should be.

    The truth is, every page on your site should be written so that it's safe to execute directly. That way you'll never make assumptions about program flow, and your code won't break when the unexpected occurs.

    Are you up for a challenge? How about writing code that uses <CFDIRECTORY> to traverse your code tree to find all CFM pages, then looping through each one, executing it via <CFHTTP> to see which ones throw errors and which work. You could call this code daily (or weekly or monthly) and e-mail yourself the results so you'll know as soon as possible if things might break.

    Changes in Site Usage
    Another phenomenon that's part of Web site use is the frequency with which that use changes. Programmers anticipate that their site will be used in one way, but, inevitably, users find another way to use it. That's not a bad thing in and of itself, but it does present an interesting problem.

    All applications, not just Web-based applications, are designed so that particular parts perform better than others. This is usually because certain parts of the application are more critical and get more use, so the time and effort needed to improve and enhance the site tends to be best spent on these parts.

    The application hums along nicely, handling the load thrown at it, and everything works well until those pesky users start using your site in ways you didn't expect. Suddenly the efficient and highly optimized parts are being executed less and less, and the less fine-tuned (I'm being generous) parts start to buckle under the growing load.

    This is actually a very common problem. Some of the largest and most impressive sites on the Internet have fallen victim to it.

    The good news is that ColdFusion provides you with an invaluable (and frequently overlooked) tool you can use to identify these potential trouble spots. The ColdFusion Administrator (starting in version 4) features a checkbox that, when checked, allows you to log page requests that take longer than a specified amount of time.

    Again, the key here is to expect the unexpected and be ready when it occurs. Individual log entries aren't necessarily indicative of a problem, but repeated entries most definitely are. I'd strongly advise all site administrators to enable this option, even on production sites. Determine what the "normal" response time should be (and then pad that number a little) and have ColdFusion log all page requests that take longer. If specific pages start appearing in the log repeatedly, you'll know where to spend your fine-tuning and performance-enhancing efforts.

    Up for another challenge? Write a scheduled event that checks this log file daily for new entries. If it finds any, it should e-mail them to you so you'll know about them immediately.

    When Bad Things Happen
    You've cleaned up your site. You no longer expect specific program flow, nor do you expect specific usage patterns. That's great, but it's not enough.

    The other big trouble spot is reliance on other systems and technologies. Whether it's database integration, execution of third-party objects and components, or interaction with other Internet protocols (like HTTP, FTP and NNTP), the more you rely on other systems and technologies, the more room there is for something to go wrong.

    Whether it's database failure, the inability to connect to a specific host, or errors and problems in calls resources, they're all your problem because to the end user your site is broken. It's not an ideal world out there; bad things do happen and you'll be blamed. And you're not going to escape this one anytime soon.

    So what do you do? Again, ColdFusion (version 4 or later) provides a tool to respond to these situations - try catch error handling. While full coverage of try catch is beyond the scope of this column (I'll devote an entire column to error handling in the future), here's the basic idea.

    Try catch error handling allows you to trap errors in your code, then pick up the processing elsewhere when an error occurs. The basic page layout looks like this:

    <CFTRY>
    ... page goes here ...
    <CFCATCH>
    ... error processing goes here ...
    </CFCATCH>
    </CFTRY>

    By wrapping an entire page between <CFTRY> and </CFTRY> tags, any error that occurs within that page will be trapped. As soon as an error is caught, processing will be taken over by the catch block (the code between <CFCATCH> and </CFCATCH>). There's no limit to what you can place in the catch block-you can change variables, redirect requests, generate e-mail, write logs and even try to fix error conditions.

    Experienced developers take this one step further by nesting try catch error handling. Generic error handling is implemented at the page level, and additional error handling is implemented around specific features or functions. This type of implementation provides the greatest level of control and allows developers to not just expect the unexpected, but also to handle the unexpected.

    Conclusion
    The Internet is a highly dynamic and configurable environment. With all that flexibility and power comes the need for greater caution and planning to ensure that applications don't suddenly break. Bugfree code is a wonderful ideal, but for most of us, writing good code that doesn't break in unexpected scenarios is as close as we'll get to attaining it.

    The bottom line is that as developers writing code for this new environment, we must all expect the unexpected- because it's going to happen and usually at the least opportune time.

  • More Stories By Ben Forta

    Ben Forta is Adobe's Senior Technical Evangelist. In that capacity he spends a considerable amount of time talking and writing about Adobe products (with an emphasis on ColdFusion and Flex), and providing feedback to help shape the future direction of the products. By the way, if you are not yet a ColdFusion user, you should be. It is an incredible product, and is truly deserving of all the praise it has been receiving. In a prior life he was a ColdFusion customer (he wrote one of the first large high visibility web sites using the product) and was so impressed he ended up working for the company that created it (Allaire). Ben is also the author of books on ColdFusion, SQL, Windows 2000, JSP, WAP, Regular Expressions, and more. Before joining Adobe (well, Allaire actually, and then Macromedia and Allaire merged, and then Adobe bought Macromedia) he helped found a company called Car.com which provides automotive services (buy a car, sell a car, etc) over the Web. Car.com (including Stoneage) is one of the largest automotive web sites out there, was written entirely in ColdFusion, and is now owned by Auto-By-Tel.

    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
    SYS-CON Media announced that Splunk, a provider of the leading software platform for real-time Operational Intelligence, has launched an ad campaign on Big Data Journal. Splunk software and cloud services enable organizations to search, monitor, analyze and visualize machine-generated big data coming from websites, applications, servers, networks, sensors and mobile devices. The ads focus on delivering ROI - how improved uptime delivered $6M in annual ROI, improving customer operations by mining large volumes of unstructured data, and how data tracking delivers uptime when it matters most.
    Scott Jenson leads a project called The Physical Web within the Chrome team at Google. Project members are working to take the scalability and openness of the web and use it to talk to the exponentially exploding range of smart devices. Nearly every company today working on the IoT comes up with the same basic solution: use my server and you'll be fine. But if we really believe there will be trillions of these devices, that just can't scale. We need a system that is open a scalable and by using the URL as a basic building block, we open this up and get the same resilience that the web enjoys.
    Code Halos - aka "digital fingerprints" - are the key organizing principle to understand a) how dumb things become smart and b) how to monetize this dynamic. In his session at @ThingsExpo, Robert Brown, AVP, Center for the Future of Work at Cognizant Technology Solutions, outlined research, analysis and recommendations from his recently published book on this phenomena on the way leading edge organizations like GE and Disney are unlocking the Internet of Things opportunity and what steps your organization should be taking to position itself for the next platform of digital competition.
    In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect at GE, and Ibrahim Gokcen, who leads GE's advanced IoT analytics, focused on the Internet of Things / Industrial Internet and how to make it operational for business end-users. Learn about the challenges posed by machine and sensor data and how to marry it with enterprise data. They also discussed the tips and tricks to provide the Industrial Internet as an end-user consumable service using Big Data Analytics and Industrial Cloud.
    How do APIs and IoT relate? The answer is not as simple as merely adding an API on top of a dumb device, but rather about understanding the architectural patterns for implementing an IoT fabric. There are typically two or three trends: Exposing the device to a management framework Exposing that management framework to a business centric logic Exposing that business layer and data to end users. This last trend is the IoT stack, which involves a new shift in the separation of what stuff happens, where data lives and where the interface lies. For instance, it's a mix of architectural styles ...
    The Internet of Things (IoT) promises to evolve the way the world does business; however, understanding how to apply it to your company can be a mystery. Most people struggle with understanding the potential business uses or tend to get caught up in the technology, resulting in solutions that fail to meet even minimum business goals. In his session at @ThingsExpo, Jesse Shiah, CEO / President / Co-Founder of AgilePoint Inc., showed what is needed to leverage the IoT to transform your business. He discussed opportunities and challenges ahead for the IoT from a market and technical point of vie...
    IoT is still a vague buzzword for many people. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed the business value of IoT that goes far beyond the general public's perception that IoT is all about wearables and home consumer services. He also discussed how IoT is perceived by investors and how venture capitalist access this space. Other topics discussed were barriers to success, what is new, what is old, and what the future may hold. Mike Kavis is Vice President & Principal Cloud Architect at Cloud Technology Pa...
    The Internet of Things (IoT) is rapidly in the process of breaking from its heretofore relatively obscure enterprise applications (such as plant floor control and supply chain management) and going mainstream into the consumer space. More and more creative folks are interconnecting everyday products such as household items, mobile devices, appliances and cars, and unleashing new and imaginative scenarios. We are seeing a lot of excitement around applications in home automation, personal fitness, and in-car entertainment and this excitement will bleed into other areas. On the commercial side, m...
    Dale Kim is the Director of Industry Solutions at MapR. His background includes a variety of technical and management roles at information technology companies. While his experience includes work with relational databases, much of his career pertains to non-relational data in the areas of search, content management, and NoSQL, and includes senior roles in technical marketing, sales engineering, and support engineering. Dale holds an MBA from Santa Clara University, and a BA in Computer Science from the University of California, Berkeley.
    The Industrial Internet revolution is now underway, enabled by connected machines and billions of devices that communicate and collaborate. The massive amounts of Big Data requiring real-time analysis is flooding legacy IT systems and giving way to cloud environments that can handle the unpredictable workloads. Yet many barriers remain until we can fully realize the opportunities and benefits from the convergence of machines and devices with Big Data and the cloud, including interoperability, data security and privacy.
    The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
    "People are a lot more knowledgeable about APIs now. There are two types of people who work with APIs - IT people who want to use APIs for something internal and the product managers who want to do something outside APIs for people to connect to them," explained Roberto Medrano, Executive Vice President at SOA Software, in this SYS-CON.tv interview at Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
    Performance is the intersection of power, agility, control, and choice. If you value performance, and more specifically consistent performance, you need to look beyond simple virtualized compute. Many factors need to be considered to create a truly performant environment. In his General Session at 15th Cloud Expo, Harold Hannon, Sr. Software Architect at SoftLayer, discussed how to take advantage of a multitude of compute options and platform features to make cloud the cornerstone of your online presence.
    In this Women in Technology Power Panel at 15th Cloud Expo, moderated by Anne Plese, Senior Consultant, Cloud Product Marketing at Verizon Enterprise, Esmeralda Swartz, CMO at MetraTech; Evelyn de Souza, Data Privacy and Compliance Strategy Leader at Cisco Systems; Seema Jethani, Director of Product Management at Basho Technologies; Victoria Livschitz, CEO of Qubell Inc.; Anne Hungate, Senior Director of Software Quality at DIRECTV, discussed what path they took to find their spot within the technology industry and how do they see opportunities for other women in their area of expertise.
    DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete at launch. DevOps may be disruptive, but it is essential.
    Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
    The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, discussed how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money!
    The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
    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...
    "There is a natural synchronization between the business models, the IoT is there to support ,” explained Brendan O'Brien, Co-founder and Chief Architect of Aria Systems, in this SYS-CON.tv interview at the 15th International Cloud Expo®, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.