Welcome!

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

Related Topics: ColdFusion

ColdFusion: Article

Model-View-Controller for You and Me

Building an MVC application in ColdFusion isn't Hard

I saw a one-man band once, and it was quite a sight. He had a bass drum on his back, operated by a cog attached to one ankle, thumping as he stomped his foot. Shoestrings tied to the neck of his guitar would move drumsticks attached to a snare drum perched atop the bass drum.

Another string attached to his right elbow operated a cymbal clamped to the side of the snare drum. I spotted duct tape in more than one place. It was a little complicated, and changing anything was bound to affect everything else.

Does this sound like an application you may have worked on? I'll admit it: it sure sounds familiar to me.

Now, I've also seen some very good orchestras. The conductor runs the show. She doesn't necessarily know how to play the viola or the sousaphone, but she knows how to use her musicians, and trusts them to do their jobs.

I don't know about you, but I'd much rather be a conductor. My musicians could change how their instruments worked, but as long as they still played in tune, it wouldn't matter to me. More importantly, I can add new instruments without having to learn to play them or figuring out how to tie, clamp, tape, and/or tack weld them into place.

That's a powerful paradigm, and this power is what the Model-View-Controller (MVC) design pattern gives you.

What Is Model-View-Controller?

According to James Dempsey's "Model-View-Controller Song," MVC is a way of organizing your code into "functional segments so your brain does not explode." MVC divides your application into three layers, each with a clearly defined task:

Model
The Model contains all of the business logic and data in your application. It is not a stretch to say that your Model literally is your application. Typically, a Model consists entirely of objects or services such as CFCs, Java classes, and / or Web Services. A Model never has any knowledge of Views or Controllers.

View
A View is what the user sees, and is how the user interacts with your application. The View's job is to allow user input and display the "state of the Model," an Object-Oriented (OO) way of saying "your application's data." Most often, Views are traditional ColdFusion pages (.cfm). Other mediums such as Flash can also act as views. Because your Model isn't aware of the Views, you can interchange views without affecting your overall application.

Controller
The Controller is simply "glue" code that passes data back and forth between the View and the Model. The Controller takes data from the user, such as form data, and gives it to the Model for processing. The results are then given back to the View, which is shown to the user.

While some users of MVC may object to passing the data back through the Controller, it's a common way to implement the MVC pattern in a Web environment. In a desktop application, however, the View might be allowed to ask the Model for its state information directly. However, because of the nature of the Web, it's a lot easier to simply "push" the state information into the View through the Controller.

Why Use Model-View-Controller?

I'm sure we've all heard talk about separating "business logic" from "presentation logic," and MVC does exactly that. By putting the Controller in between the Model (business logic) and View (presentation), we're insuring that they're not only separate, but highly reusable because they're not specific to a particular implementation. Additional Views can use the same Model without any modification. More importantly, the internal working of the Model can change without affecting the Views. This should sound familiar: we've arrived at the power described earlier when I said I'd rather be a conductor than a one-man band. Let's revisit what I said earlier, but change a few words:

"My components could change how their internals worked, but as long as they kept the same interface, it wouldn't matter to me. More importantly, I can add new components without having to learn how they work, just how to use them."

That's a very powerful statement to make about application design. Model-View-Controller utilizes Object-Oriented Design concepts known as "decoupling" and "separation of concerns" to achieve this power. In a "traditional" ColdFusion application, each page is responsible for a good deal: business logic, data access logic, presentation logic, and data validation. By isolating the business logic in the Model and the presentation logic in the View and having the two communicate through the Controller, we've "decoupled" the business layer from the presentation layer. Each of the three layers has a responsibility, or "concern" that is separate from the others. As long as the boundaries along which the layers communicate, or "interfaces," remain the same each layer can change its internal functionality without affecting other the other two.

Let's Code: An MVC Example

Building an MVC application in ColdFusion isn't very hard. You'll just need a good understanding of ColdFusion Components (CFCs) and an open mind. If you're not up and running with ColdFusion Components, you may want to read Jeffry Houser's article entitled "ColdFusion Components" when you're through with this article (CFDJ vol. 6, issue 11).

First, we need a problem to Model. For a fun example, I've chosen to Model translation of English phrases into Pig Latin. For our first attempt, I'm implementing a very simple version of Pig Latin - for any given word, move all consonants until the first vowel to the end of the word, and then add "ay." For example, "Model-View-Controller" becomes "odelMay iewVay ontrollerCay."

It's easy enough to encapsulate all the logic for this into a CFC. Listing 1 shows the entire model for our application, contained in PigLatinizer.cfc. You'll see that it has a single method ("Translate") that receives a string, and returns a translated string. At this point, we have a working "Model" of our "problem domain" - translating phrases into Pig Latin.

Now, we need a View to interact with our model. Listing 2 shows our basic translator form. It has a form field that collects a phrase to translate, a submit button, and will optionally show results of the latest translation.

Well, that was easy. We have a Model and View. Now we need a Controller to glue the two together. One approach many have taken is to simply add pseudo-Controller code to the top of their View pages, closely mimicking the standard self-posting form architecture ColdFusion developers have used for years. However, this places the Controller code in your View, eliminating any chance of re-use. Instead of doing this, we're going to use a CFC called PigLatinController. The source code for PigLatinController.cfc is shown in Listing 3. Examining the code reveals that it's pretty simple. There's an empty constructor ("Init") and a single method ("Translate"). While our constructor here remains empty, in the real world, this may be a place to insert information, such as datasource names or other configuration data, that the controller will need to pass along to the Model.

Examining the Translate method shows a controller in action. It first creates the needed portions of the model - in this case, simply an instance of PigLatinizer.cfc. It then passes data from the View (form.phrase) to the Translate method of the PigLatinizer. The user is then redirected to the view, with the resulting translation passed as a URL variable.

Now we have a Model, a View, and a Controller. What we're still lacking, however, is a way to have them all "talk." This is a where a framework is needed.

Building a Simple Framework

While there are two popular frameworks available for what we need to do (Fusebox and Mach-II), we're going to build our own mini-framework using about ten lines of code. It's going to be bare-bones, but it should get the job done while also introducing the need for more robust, application-agnostic frameworks.

Listing 4 shows our Pig Latin's Application.cfm file, where lines 3 - 13 represent our framework. First, we see if the application is initialized. If it's not, we create an instance of our Controller, placing it into the application scope. Second, we examine the URL scope to see if a parameter named "method" exists. If it does, we CFInvoke that method of our controller.

Running Our Application

We've now built a complete MVC application for translating phrases to Pig Latin. Let's step through two page requests, initial and form post, to trace how the pieces of MVC work together.

Initially, the user requests Index.cfm. ColdFusion processes the Application.cfm file. Our framework insures that an instance of PigLatinController (the Controller) exists in the application scope, and then looks for URL.Method. Because URL.Method doesn't exist, no action is taken. Index.cfm (the View) then presents the user with the appropriate form.

The user then enters a phrase and clicks the submit button, and our next request cycle begins.

Again, ColdFusion processes the Application.cfm file and insures that our Controller exists. This time, however, URL.Method is defined, and its value is "Translate." Our mini-framework recognizes this, and invokes the "Translate" method of the Controller.

Inside the Controller, the "Translate" method creates an instance of PigLatinizer (our Model). It passes the data from the View (form.phrase) into the Model's "Translate" method, and collects the result. The Controller then CFLocates the user back to Index.cfm, appending the result of the translation to the URL. Index.cfm, the View, shows the "state of the model" (the translated phrase), and dutifully re-displays the translation form.

Modifying Our Application

Because we've placed the Controller between the Model and the View, changes to the Model won't affect the View, and vice versa. Realizing our implementation of Pig Latin isn't complete and that there are additional rules for handling words beginning with vowels, we need to modify our Model. Luckily, there's a freely available Java class that translates English into Pig Latin. We can modify our Model to use this class instead of its own internal logic (Listing 5 shows this modification). Because we're only changing its internals, and not altering its interface, the rest of our application will remain unaffected. By isolating our changes, and decoupling our business logic from our presentation logic, we've given ourselves a both more powerful and safer way to alter or scale our application.

The Need for Frameworks

Our bare-bones framework is fine for our Pig-Latin translator, but I wouldn't want to develop an enterprise application with it. On a low level, the method of processing input in the controller then CFLocating would make it hard to return meaningful validation results - the URL string could become huge! On a higher level, what if one method of the Controller needed to call another method? It'd be easy to add the code to do so, but this may begin to fall outside of the "concern" of the controller (passing data between the View and the Model) and may begin to fall into the realm of business logic or application design. Frameworks such as Fusebox and Mach-II help out in this problem. By removing this control of "flow" from the Controller and letting you organize your application using XML, they both allow the Controller to assume its proper role of passing data. Frameworks have a number of other advantages, but that's another article.

Summary

Model-View-Controller is an elegant way to divide your application into logical layers. Each layer has a single job, and does it well. The Model represents your application's business logic. The View presents data from the Model, and accepts user input. The Controller serves to pass data between the View and the Model. Most importantly, the Controller serves to decouple the View from the Model, isolating what changes to bring unprecedented power to your application's design.

Further Reading

This article provided a high-level introduction to Model-view-controller. Hopefully, it's gotten you interested in using MVC to simplify and enhance your application designs. However, it's glossed over a good deal of Object-Oriented concepts and terminology. There's a lot to learn about the theory of MVC and the various design patterns that are used inside of it (MVC is technically a "compound" pattern, made up of other design patterns).

If you're ready to jump into using MVC for ColdFusion applications, I'd begin by taking a look at the Fusebox (www.fusebox.org), Model-Glue (www.model-glue.com) and Mach-II (www.mach-ii.com) frameworks.".

More Stories By Joe Rinehart

Joe Rinehart is a Flex, ColdFusion, and J2EE developer. You can find his blog at Firemoss.com.

Comments (1)

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
Samsung VP Jacopo Lenzi, who headed the company's recent SmartThings acquisition under the auspices of Samsung's Open Innovaction Center (OIC), answered a few questions we had about the deal. This interview was in conjunction with our interview with SmartThings CEO Alex Hawkinson. IoT Journal: SmartThings was developed in an open, standards-agnostic platform, and will now be part of Samsung's Open Innovation Center. Can you elaborate on your commitment to keep the platform open? Jacopo Lenzi: Samsung recognizes that true, accelerated innovation cannot be driven from one source, but requires a...
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at Internet of @ThingsExpo, Robin Raymond, Chief Architect at Hookflash Inc., will walk through the shifting landscape of traditional telephone a...
BSQUARE is a global leader of embedded software solutions. We enable smart connected systems at the device level and beyond that millions use every day and provide actionable data solutions for the growing Internet of Things (IoT) market. We empower our world-class customers with our products, services and solutions to achieve innovation and success. For more information, visit www.bsquare.com.
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.
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 style...
SYS-CON Events announced today that SOA Software, an API management leader, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. SOA Software is a leading provider of API Management and SOA Governance products that equip business to deliver APIs and SOA together to drive their company to meet its business strategy quickly and effectively. SOA Software’s technology helps businesses to accelerate their digital channels with APIs, drive partner adoption, monetize their assets, and achieve a...
From a software development perspective IoT is about programming "things," about connecting them with each other or integrating them with existing applications. In his session at @ThingsExpo, Yakov Fain, co-founder of Farata Systems and SuranceBay, will show you how small IoT-enabled devices from multiple manufacturers can be integrated into the workflow of an enterprise application. This is a practical demo of building a framework and components in HTML/Java/Mobile technologies to serve as a platform that can integrate new devices as they become available on the market.
SYS-CON Events announced today that Utimaco will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Utimaco is a leading manufacturer of hardware based security solutions that provide the root of trust to keep cryptographic keys safe, secure critical digital infrastructures and protect high value data assets. Only Utimaco delivers a general-purpose hardware security module (HSM) as a customizable platform to easily integrate into existing software solutions, embed business logic and build s...
Connected devices are changing the way we go about our everyday life, from wearables to driverless cars, to smart grids and entire industries revolutionizing business opportunities through smart objects, capable of two-way communication. But what happens when objects are given an IP-address, and we rely on that connection, sometimes with our lives? How do we secure those vast data infrastructures and safe-keep the privacy of sensitive information? This session will outline how each and every connected device can uphold a core root of trust via a unique cryptographic signature – a “bir...
Internet of @ThingsExpo Silicon Valley announced on Thursday its first 12 all-star speakers and sessions for its upcoming event, which will take place November 4-6, 2014, at the Santa Clara Convention Center in California. @ThingsExpo, the first and largest IoT event in the world, debuted at the Javits Center in New York City in June 10-12, 2014 with over 6,000 delegates attending the conference. Among the first 12 announced world class speakers, IBM will present two highly popular IoT sessions, which will take place November 4-6, 2014 at the Santa Clara Convention Center in Santa Clara, Calif...
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.
WebRTC defines no default signaling protocol, causing fragmentation between WebRTC silos. SIP and XMPP provide possibilities, but come with considerable complexity and are not designed for use in a web environment. In his session at Internet of @ThingsExpo, Matthew Hodgson, technical co-founder of the Matrix.org, will discuss how Matrix is a new non-profit Open Source Project that defines both a new HTTP-based standard for VoIP & IM signaling and provides reference implementations.

SUNNYVALE, Calif., Oct. 20, 2014 /PRNewswire/ -- Spansion Inc. (NYSE: CODE), a global leader in embedded systems, today added 96 new products to the Spansion® FM4 Family of flexible microcontrollers (MCUs). Based on the ARM® Cortex®-M4F core, the new MCUs boast a 200 MHz operating frequency and support a diverse set of on-chip peripherals for enhanced human machine interfaces (HMIs) and machine-to-machine (M2M) communications. The rich set of periphera...

SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue business and deliver exceptional experiences to their customers.
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce the value of the network in helping organizations to maximize their company’s cloud experience.
The Internet of Things (IoT) is making everything it touches smarter – smart devices, smart cars and smart cities. And lucky us, we’re just beginning to reap the benefits as we work toward a networked society. However, this technology-driven innovation is impacting more than just individuals. The IoT has an environmental impact as well, which brings us to the theme of this month’s #IoTuesday Twitter chat. The ability to remove inefficiencies through connected objects is driving change throughout every sector, including waste management. BigBelly Solar, located just outside of Boston, is trans...
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.
Predicted by Gartner to add $1.9 trillion to the global economy by 2020, the Internet of Everything (IoE) is based on the idea that devices, systems and services will connect in simple, transparent ways, enabling seamless interactions among devices across brands and sectors. As this vision unfolds, it is clear that no single company can accomplish the level of interoperability required to support the horizontal aspects of the IoE. The AllSeen Alliance, announced in December 2013, was formed with the goal to advance IoE adoption and innovation in the connected home, healthcare, education, aut...
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...