Welcome!

You will be redirected in 30 seconds or close now.

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

Related Topics: ColdFusion

ColdFusion: Article

Creating Configuration Files

Make your work cleaner and easier to maintain

In their book Head First Design Patterns, the four coauthors lay out a series of key principles for creating robust software designs. One of the most important of these principles is "Find what varies and encapsulate it." In this article, let's apply this principle to the use of configuration files and explore the support for old-style .INI files and XML files.

"Find what varies and encapsulate it" is what most of us do for a living. The heart of any programming language is a variable - a name/value pair. Although we programmers are so used to a variable that it seems the most natural of things, people without a programming background don't find it natural at all.

What Exactly Is a Variable?

I learned this several years ago when my son was working on a presentation he would have to give to his fifth-grade class. At the time, he was working with a video game called "RPG Maker" (a devilishly clever introduction to computer programming that masquerades as a game) and he decided that he would explain the very basic underpinnings of computer programming languages.

"Hey, Dad - how would you explain a variable?"

"A variable? Well, that's simple. A variable is something whose actual value may change over time. Take, for example, the notion of where you live - a notion we might call homeAddress. Now, the value of homeAddress may change (if you move from one house to another) but the idea of homeAddress is permanent.

And that's a variable."

Sometimes, I just have a way of making hard things seem simple. It's a gift.

Our son tried out his presentation on my wife. Susie isn't a programmer, but she works for IBM and so some computer basics must have worked its way into her, right?

She stared blankly at our son trying to explain how the idea of your homeAddress is the same even though it may change - your home address, the value, not the idea (which stays the same). Or something.

I went to hear his presentation to his classmates and it was pretty clear that the idea of variables wasn't having any better success with them than it had with his mom.

And there's an epilogue to this story. Some time later, Steve Nelson (of Fusebox fame) and I were discussing some Fusebox-related matters and I happened to tell him the story of how my "homeAddress" example crashed and burned. As you would expect of a friend, Steve was properly sympathetic.

"Hal, you're an idiot," he began. "Don't use abstract terms when trying to explain things to people. Give them something they can touch and see."

"Like what?" I asked.

Steve was drinking a Coke at the time in a clear plastic bottle. "You see this bottle? That's the variable. See the Coke inside it? That's the value."

He poured out the remaining liquid and dropped a pencil into the bottle. "Same variable, but different value."

Hmmm...in his obviously simplistic way, which left out many important nuances, he did seem to have a point. Now, it was my job to crush Steve's argument underfoot so that I would emerge victorious!

"All right, smart guy," I said. "How would you explain - an array?"

Steve stopped. It seemed that victory was mine. "An array?" he said. "Well...that's a six-pack!"

Variables in Applications

This month, I want to apply the "find what varies and encapsulate it" principle within a broader context - that of entire applications.

Almost every application of moderate size or more has certain pieces of information that the code relies on. Here are some examples:

  • dsn
  • log_file_path
  • expiration_date
  • banner_image
  • verbose_messages
  • required_score
  • admin_email
  • company_name
In each of these cases, the data is specific to a particular installation, so that the only thing different about installation A from installation B is that the dsn or the company_name or the decision to turn verbose messages on or off (etc.) is different. We have, in other words, a variable.

But where should this information be stored? It might be stored in a database. Sometimes, though, this isn't a good option. It may be that there is no login that would identify a particular user. Or it may be that the information needs to be maintained by non-programmers and no user-friendly interface to a database exists. And If the needed information is so simple that a database isn't required - or so complex that modeling in a database is difficult - a better solution may be a configuration file.

Two types of configuration file have found widespread acceptance in the programming world. The first is a bit of "old school" - the INI file. First popularized by Microsoft, the ini file has a specific, simple format:


[SectionName]
keyname=value
;comment
keyname=value, value, value ;used when a keyname has multiple values

Section- and keynames cannot contain spaces and are case-insensitive. So, a sample INI file might look like this:


[Configuration]
dsn=WegotWidgets
company_name =Widget Masters
verbose_messages = true

Notice the slight inconsistencies of treatment of spaces by the equal sign. Part of the INI specification is that parsers should be liberal in their application of rules.

How do we make use of INI files? We'll need to be able to both read and write to these files and ColdFusion makes it easy to do both of these. Let's first take the case of reading an INI file. We'll use the one shown above as our example. To read one of the name/value pairs - say, company_name - we'll use ColdFusion's GetProfileString function.


<cfoutput>
	<h2>Welcome to #GetProfileString(ExpandPath('Sample.ini'), 'Configuration',
	'company_name')#</h2>
</cfoutput>

How do we get the value of "Widget Masters" into the INI file? Usually, these files are edited by hand, but ColdFusion allows you to edit them programatically. In this example, I'll add a new name/value pair to Sample.ini.


<cfset SetProfileString(ExpandPath('Sample.ini'), 'Configuration', 'required_score', 90) />

<cfoutput>
	<cfif variables.score LT GetProfileString(ExpandPath('Sample.ini'), 'Configuration',
	'required_score')>
		Have you considered a career in the arts?
	<cfelse>
		OK, now you can receive the secret Java decoder ring.
	</cfif>
</cfoutput>

If you're wondering why you would need to set an INI file programatically, consider that this file can be used to determine the next numbered item in a sequence - an order number or customer number for example. To do this, you get, then immediately set, the number stored in the INI file.


<cfset invoice = GetProfileString(ExpandPath('Sample.ini'), 'Configuration', 'last_invoice') />
<cfset SetProfileString(ExpandPath('Sample.ini'), 'Configuration', 'last_invoice', invoice + 1) />

Invoice No: #invoice#

Some configuration information is more complex and is a poor fit for the simple nature of the INI file. In such cases, XML can be the ideal solution. Here is a sample XML-based configuration file:


<configuration>
	<settings>
		<!-- database use = testing|production-->
		<database use="testing">

			<testing>
				<dsn name="TestInventory" />
				<db type="msaccess" />
			</testing>
			<production>
				<dsn name="GlobalInventory" security="SSPI" />
				<db type="sqlserver" />
			</production>
		</database>
	</settings>
</configuration>

The idea with this configuration file is that the application may be in one of two modes: testing or production. Each mode uses a separate datasource. When the "use" attribute of the "database" element is set to testing, we want to use the datasource defined in the "testing" element; in production mode, we want to use the datasource defined in the "production" element. Here is the code that reads and process the configuration file shown above:


<cffile action="READ" file="#ExpandPath('Sample.xml')#" variable="aFile" />
<cfset xml = XmlParse(aFile) />

<cfset databaseInfo = XmlSearch(xml, '//database') />
<cfset use = databaseInfo[1].xmlAttributes['use'] />
<cfset testingInfo = XmlSearch(xml, '//testing/dsn') />
<cfset productionInfo = XmlSearch(xml, '//production/dsn') />
<cfset testing = testingInfo[1].xmlAttributes['name'] />
<cfset production = productionInfo[1].xmlAttributes['name'] />

<cfset dsn = Evaluate(use) />

<cfquery datasource="#dsn#" name="myQ">
	<!---sql here--->
</cfquery>

ColdFusion offers several XML tags and functions for dealing with XML. In this case, I've used only two: XMLParse and XMLSearch. The XMLParse function converts valid XML text into an XML object. Without this step, the XML text is unavailable for further processing.

The XMLSearch function provides an interface to the tremendous power of XPath, the XML-specific language for querying XML objects. For developers steeped in SQL queries, XPath may be initially hard to digest, but there are some excellent resources to help you.

Nate Weiss wrote a fine tutorial on working with ColdFusion's XML tags and functions, available at www.macromedia.com/devnet/mx/coldfusion/articles/xmlxslt.pdf. For in-depth examples of working with XPath, the tutorials at www.zvon.org/xxl/XPathTutorial/General/examples.html are invaluable.

Configuration files are very specific tools, but understanding how to use them can make your work cleaner and easier to maintain.

Further References Head First Design Patterns
By Elisabeth & Eric Freeman, Bert Bates, Kathy Sierra (O'Reilly)

More Stories By Hal Helms

Hal Helms is a well-known speaker/writer/strategist on software development issues. He holds training sessions on Java, ColdFusion, and software development processes. He authors a popular monthly newsletter series. For more information, contact him at hal (at) halhelms.com or see his website, www.halhelms.com.

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.


IoT & Smart Cities Stories
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
Digital Transformation is much more than a buzzword. The radical shift to digital mechanisms for almost every process is evident across all industries and verticals. This is often especially true in financial services, where the legacy environment is many times unable to keep up with the rapidly shifting demands of the consumer. The constant pressure to provide complete, omnichannel delivery of customer-facing solutions to meet both regulatory and customer demands is putting enormous pressure on...
IoT is rapidly becoming mainstream as more and more investments are made into the platforms and technology. As this movement continues to expand and gain momentum it creates a massive wall of noise that can be difficult to sift through. Unfortunately, this inevitably makes IoT less approachable for people to get started with and can hamper efforts to integrate this key technology into your own portfolio. There are so many connected products already in place today with many hundreds more on the h...
The standardization of container runtimes and images has sparked the creation of an almost overwhelming number of new open source projects that build on and otherwise work with these specifications. Of course, there's Kubernetes, which orchestrates and manages collections of containers. It was one of the first and best-known examples of projects that make containers truly useful for production use. However, more recently, the container ecosystem has truly exploded. A service mesh like Istio addr...
Digital Transformation: Preparing Cloud & IoT Security for the Age of Artificial Intelligence. As automation and artificial intelligence (AI) power solution development and delivery, many businesses need to build backend cloud capabilities. Well-poised organizations, marketing smart devices with AI and BlockChain capabilities prepare to refine compliance and regulatory capabilities in 2018. Volumes of health, financial, technical and privacy data, along with tightening compliance requirements by...
Charles Araujo is an industry analyst, internationally recognized authority on the Digital Enterprise and author of The Quantum Age of IT: Why Everything You Know About IT is About to Change. As Principal Analyst with Intellyx, he writes, speaks and advises organizations on how to navigate through this time of disruption. He is also the founder of The Institute for Digital Transformation and a sought after keynote speaker. He has been a regular contributor to both InformationWeek and CIO Insight...
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 settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
To Really Work for Enterprises, MultiCloud Adoption Requires Far Better and Inclusive Cloud Monitoring and Cost Management … But How? Overwhelmingly, even as enterprises have adopted cloud computing and are expanding to multi-cloud computing, IT leaders remain concerned about how to monitor, manage and control costs across hybrid and multi-cloud deployments. It’s clear that traditional IT monitoring and management approaches, designed after all for on-premises data centers, are falling short in ...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...