|By Joe Rinehart||
|April 13, 2005 12:00 AM EDT||
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:
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.
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.
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 ExampleBuilding 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 FrameworkWhile 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 ApplicationWe'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 ApplicationBecause 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 FrameworksOur 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.
SummaryModel-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 ReadingThis 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.".
|Derek 05/04/05 10:45:24 AM EDT|
Where is the sample code for this?
In 2015, 4.9 billion connected "things" will be in use. By 2020, Gartner forecasts this amount to be 25 billion, a 410 percent increase in just five years. How will businesses handle this rapid growth of data? Hadoop will continue to improve its technology to meet business demands, by enabling businesses to access/analyze data in real time, when and where they need it. Cloudera's Chief Technologist, Eli Collins, will discuss how Big Data is keeping up with today's data demands and how in the future, data and analytics will be pervasive, embedded into every workflow, application and infra...
Apr. 20, 2015 08:45 PM EDT Reads: 870
Participants will reach the final if their IoT solution is liked. A community vote will determine the best solutions submitted in each country, after which an expert jury will select the national winners and the best international IoT solution. Each country's best solution can win a national marketing campaign worth up to €30,000 and become a partner in Deutsche Telekom's participating markets. The winning international solution can become partner of Deutsche Telekom Group across all eight countries and reach out to a potential of 10,8 million business customers. Deutsche Telekom Group has a...
Apr. 20, 2015 05:00 PM EDT Reads: 815
The best mobile applications are augmented by dedicated servers, the Internet and Cloud services. Mobile developers should focus on one thing: writing the next socially disruptive viral app. Thanks to the cloud, they can focus on the overall solution, not the underlying plumbing. From iOS to Android and Windows, developers can leverage cloud services to create a common cross-platform backend to persist user settings, app data, broadcast notifications, run jobs, etc. This session provides a high level technical overview of many cloud services available to mobile app developers, includi...
Apr. 20, 2015 04:00 PM EDT Reads: 462
Health care systems across the globe are under enormous strain, as facilities reach capacity and costs continue to rise. M2M and the Internet of Things have the potential to transform the industry through connected health solutions that can make care more efficient while reducing costs. In fact, Vodafone's annual M2M Barometer Report forecasts M2M applications rising to 57 percent in health care and life sciences by 2016. Lively is one of Vodafone's health care partners, whose solutions enable older adults to live independent lives while staying connected to loved ones. M2M will continue to gr...
Apr. 20, 2015 03:00 PM EDT Reads: 1,100
SYS-CON Events announced today that Vicom Computer Services, Inc., a provider of technology and service solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. They are located at booth #427. Vicom Computer Services, Inc. is a progressive leader in the technology industry for over 30 years. Headquartered in the NY Metropolitan area. Vicom provides products and services based on today’s requirements around Unified Networks, Cloud Computing strategies, Virtualization around Software defined Data Ce...
Apr. 20, 2015 02:00 PM EDT Reads: 1,475
Dave will share his insights on how Internet of Things for Enterprises are transforming and making more productive and efficient operations and maintenance (O&M) procedures in the cleantech industry and beyond. Speaker Bio: Dave Landa is chief operating officer of Cybozu Corp (kintone US). Based in the San Francisco Bay Area, Dave has been on the forefront of the Cloud revolution driving strategic business development on the executive teams of multiple leading Software as a Services (SaaS) application providers dating back to 2004. Cybozu's kintone.com is a leading global BYOA (Build Your O...
Apr. 20, 2015 02:00 PM EDT Reads: 1,125
VoxImplant has announced full WebRTC support in the newest versions of its Android SDK and iOS SDK. The updated SDKs, which enable audio and video calls on mobile devices, are now compatible with the WebRTC standard to allow any mobile app to communicate with WebRTC-enabled browsers, including Google Chrome, Mozilla Firefox, Opera, and, when available, Microsoft Spartan. The WebRTC-updated SDKs represent VoxImplant's continued leadership in simplifying the development of real-time communications (RTC) services for app developers. VoxImplant (built by Zingaya, the real-time communication servi...
Apr. 20, 2015 12:45 PM EDT Reads: 1,950
What exactly is a cognitive application? In her session at 16th Cloud Expo, Ashley Hathaway, Product Manager at IBM Watson, will look at the services being offered by the IBM Watson Developer Cloud and what that means for developers and Big Data. She'll explore how IBM Watson and its partnerships will continue to grow and help define what it means to be a cognitive service, as well as take a look at the offerings on Bluemix. She will also check out how Watson and the Alchemy API team up to offer disruptive APIs to developers.
Apr. 20, 2015 12:00 PM EDT Reads: 1,585
The IoT Bootcamp is coming to Cloud Expo | @ThingsExpo on June 9-10 at the Javits Center in New York. Instructor. Registration is now available at http://iotbootcamp.sys-con.com/ Instructor Janakiram MSV previously taught the famously successful Multi-Cloud Bootcamp at Cloud Expo | @ThingsExpo in November in Santa Clara. Now he is expanding the focus to Janakiram is the founder and CTO of Get Cloud Ready Consulting, a niche Cloud Migration and Cloud Operations firm that recently got acquired by Aditi Technologies. He is a Microsoft Regional Director for Hyderabad, India, and one of the f...
Apr. 20, 2015 12:00 PM EDT Reads: 1,294
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal today!
Apr. 20, 2015 12:00 PM EDT Reads: 2,165
With IoT exploding, massive data will transform businesses with opportunities to monetize almost anything that can be measured. In this C-Level Roundtable Discussion at @ThingsExpo, Brendan O’Brien, Aria Systems Co-founder and Chief Evangelist, will lead an expert panel of consultants, thought leaders and practitioners who will look at these new monetization trends, discuss the implications, and detail lessons learned from their collective experience. Finally, the panel will point the way forward for enterprises who wish to leverage the resulting complex recurring revenue models, adding valu...
Apr. 20, 2015 10:30 AM EDT Reads: 1,517
SYS-CON Media announced today that @WebRTCSummit Blog, the largest WebRTC resource in the world, has been launched. @WebRTCSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. @WebRTCSummit Blog can be bookmarked ▸ Here @WebRTCSummit conference site can be bookmarked ▸ Here
Apr. 20, 2015 10:30 AM EDT Reads: 2,209
The WebRTC Summit 2015 New York, to be held June 9-11, 2015, at the Javits Center in New York, NY, announces that its Call for Papers is open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 16th International Cloud Expo, @ThingsExpo, Big Data Expo, and DevOps Summit.
Apr. 20, 2015 10:15 AM EDT Reads: 2,305
“In the past year we've seen a lot of stabilization of WebRTC. You can now use it in production with a far greater degree of certainty. A lot of the real developments in the past year have been in things like the data channel, which will enable a whole new type of application," explained Peter Dunkley, Technical Director at Acision, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Apr. 20, 2015 10:00 AM EDT Reads: 3,923
From telemedicine to smart cars, digital homes and industrial monitoring, the explosive growth of IoT has created exciting new business opportunities for real time calls and messaging. In his session at @ThingsExpo, Ivelin Ivanov, CEO and Co-Founder of Telestax, shared some of the new revenue sources that IoT created for Restcomm – the open source telephony platform from Telestax. Ivelin Ivanov is a technology entrepreneur who founded Mobicents, an Open Source VoIP Platform, to help create, deploy, and manage applications integrating voice, video and data. He is the co-founder of TeleStax, a...
Apr. 20, 2015 09:30 AM EDT Reads: 4,701
As enterprises move to all-IP networks and cloud-based applications, communications service providers (CSPs) – facing increased competition from over-the-top providers delivering content via the Internet and independently of CSPs – must be able to offer seamless cloud-based communication and collaboration solutions that can scale for small, midsize, and large enterprises, as well as public sector organizations, in order to keep and grow market share. The latest version of Oracle Communications Unified Communications Suite gives CSPs the capability to do just that. In addition, its integration ...
Apr. 20, 2015 09:15 AM EDT Reads: 4,024
SYS-CON Events announced today that Ciqada will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Ciqada™ makes it easy to connect your products to the Internet. By integrating key components - hardware, servers, dashboards, and mobile apps - into an easy-to-use, configurable system, your products can quickly and securely join the internet of things. With remote monitoring, control, and alert messaging capability, you will meet your customers' needs of tomorrow - today! Ciqada. Let your products take flight. For more inform...
Apr. 20, 2015 09:00 AM EDT Reads: 1,692
Can call centers hang up the phones for good? Intuitive Solutions did. WebRTC enabled this contact center provider to eliminate antiquated telephony and desktop phone infrastructure with a pure web-based solution, allowing them to expand beyond brick-and-mortar confines to a home-based agent model. It also ensured scalability and better service for customers, including MUY! Companies, one of the country's largest franchise restaurant companies with 232 Pizza Hut locations. This is one example of WebRTC adoption today, but the potential is limitless when powered by IoT.
Apr. 20, 2015 09:00 AM EDT Reads: 5,020
SYS-CON Events announced today that SoftLayer, an IBM company, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place June 9-11, 2015 at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place November 3–5, 2015 at the Santa Clara Convention Center in Santa Clara, CA. SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from ...
Apr. 20, 2015 08:45 AM EDT Reads: 2,506
SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborate. Cisco and our partners are building the platform for the Internet of Everything by connecting the...
Apr. 20, 2015 08:30 AM EDT Reads: 5,680