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

ColdFusion's Application Framework

Apply it to your development

For the past month or so, I've had the pleasure of doing some development in Lotus Domino. I worked with Domino a lot when I was just starting out my IT career, so I know it's a powerful development platform for client/server applications.

I'm sure if you're reading this, you're developing, or want to be developing, client/server applications with ColdFusion. In the Domino world, we have the Domino server and Lotus Notes client. When developing ColdFusion apps, your client is most likely Internet Explorer, Safari, or Navigator. Your Web server is probably IIS or Apache.

While juggling some Notes work with my standard Web fare, I started thinking about how the Lotus Notes client is different from a browser client. The Notes client is smart. It knows that I like my e-mail sorted by ascending date. It knows which documents I've read and which I haven't. Lotus Notes maintains my state in the application.

The browser, on the other hand, has no idea about any of these things. Every request exists in a vacuum and has no knowledge of any other request. This is a problem that plagues all Web applications, whether you're accessing your gmail account or changing your MSN home page preferences. How does the browser know what's going on? It doesn't, but thankfully in ColdFusion there is an easy way to handle this. This article will talk about ColdFusion's application framework.

cfapplication Tag
At the heart of ColdFusion's application framework is the cfapplication tag. This tag defines how ColdFusion stores application-specific and session-specific data. An application is a group of related actions or functions that work together to give the user a seamless experience. Any of the Web-based e-mail accounts, such as gmail, Yahoo Mail, or Hotmail would serve as a perfect example of a Web application. Even though there is only one application, there can be many users on it. A session keeps track of individual users.

These are the attributes of the cfapplication tag:

  • Name: The name attribute is used to accept the name of the application. ColdFusion uses the name to keep application and session data separate within the context of an application. You can have as many applications as you like on a ColdFusion server, but each one must have a different name. It is not uncommon to have a site and the site administrator running as separate applications, even though they often access the same database.

  • ApplicationTimeOut: The application timeout attribute specifies the life span of the application variables. You can specify the value of this attribute with the CreateTimeSpan function. More information on the CreateTimeSpan function can be found at http://livedocs.macromedia.com/coldfusion/ 6.1/htmldocs/functi53.htm#wp1102715. A little-known fact is that any place that you use the CreateTimeSpan function can be replaced with a constant value. For example, one day is equal to 1. Two days and 12 hours equals 2.5. You can find the specific value you need by wrapping the CreateTimeSpan function in a cfoutput, executing the template, and using the value output. Using the CreateTimeSpan function is more explicit, but using an integer value is one less function that your application has to execute. The maximum value set in the ColdFusion administrator will take precedence if this value is larger than that value. The timeout value is specified from the date of last access.

  • LoginStorage: The login storage attribute is used to specify where login information is stored. The login information is specified in ColdFusion's cflogin and cfloginuser tags. The default value is cookie, with the alternative being session.

  • SetClientCookies: By default, ColdFusion uses two values to associate sessions on the server with a specific client. The first value is CFID, which is an integer that increments. The second is CFTOKEN, which is a random number. The setClientCookies attribute tells CF whether to store these values as cookies. If set to no, you'll have to pass the CFID and CFTOKEN in the query string on each request to access session information. These values must be in the query string, so on form posts you must add them to the action attribute of the form tag, not pass them as hidden form variables. To make this easier, there is a session variable called URLToken that contains the query string with CFID and CFTOKEN. If you have J2EE sessions enabled in the ColdFusion administrator, ColdFusion will set a JsessionID value instead of CFID and CFTOKEN.

  • ClientManagement: The ClientManagement attribute is a Boolean value that tells the application whether or not to allow for client variables in the application. Client variables are similar to session variables, except that they are stored on disk instead of in memory. Client variables are better in clustered environments, because the data is accessible from all servers when stored in cookies or a central database.

  • ClientStorage: The ClientStorage attribute is used to specify the location where client variables are stored. There are three options here. The default is to store them in the registry. I wouldn't recommend ever using the registry. The registry is not designed for massive read and writes. I've also heard too many horror stories of the registry growing too big and bringing down machines. The second option is to store the client variables as browser cookies. This has advantages, such as the cookies will always exist when the user returns to the site. If you use cookies, there's a limit to the amount of data a single site can store as cookie data. The third option is my preferred (and the recommended) choice, which is to store the information in a database. You can specify the name of the data source for the value of this attribute. Storing client variables in a database is much slower than using browser cookies; however, your only size limitation is the amount of hard disk space you have. You can set the default client variable storage options in the ColdFusion administrator, although they can be overridden by the cfapplication tag.

  • SessionManagement: The SessionManagement attribute is a Boolean attribute that specifies whether session management is enabled for this application or not. The default is no.

  • SessionTimeout: The SessionTimeout attribute is similar to the ApplicationTimeout attribute. It specifies how long the session variables will exist. Its value can be set with the CreateTimeSpan function. The maximum value set in the ColdFusion administrator will take precedence if the attribute value is larger than that CF Admin value. The timeout value is referenced from the date of the last request.

  • SetDomainCookies: The SetDomainCookies attribute is used on clustered servers. Instead of setting the cookies for the host, it sets them for the full domain. That means when a user switches from one machine to another, ColdFusion will still know about the user's session. Keep in mind that session variables are not stored between requests; however, client variables stored as cookies or in a data source are, assuming that both machines have access to the same data source, of course.

    In a typical cfapplication tag, you'd probably use:

    <cfapplication name="MyApp" applicationTimeOut="1" clientstorage="MyDSN"
     setClientCookies="Yes" sessionManagement="Yes" sessionTimeOut = ".4">
    This will create the application MyApp with an application timeout of one day and a session timeout of one hour. ClientStorage will be in the MyDSN database, and the CFID and CFTOKEN values will be cookies on the user's machine. Domain cookies are not set, since that is the default behavior and we didn't specify the attribute. Login storage information will be stored as cookies, since we didn't specify that attribute either.

    Application, Session, and Client Variable Scopes
    One of the primary reasons for setting up an application with the cfapplication tag is so you can store application and session-specific data between page requests. If you do not set a cfapplication tag in a page request, you can still use variables in the application, client, or session scopes. However, there will be no way to reference the values on your next page request. You should always set up your application using the cfapplication tag.

    Because variables in the application, client, and session scopes persist between requests, you often need to set them only on application or session initialization, respectively. Unfortunately, ColdFusion does not have a way to execute code when a session or application is initialized. There is a great Java workaround for this. You can read more about it in "Making the Most of J2EE Event Listeners," by Eric Brancaccio in the May 2004 edition of CFDJ. You may also want to tell Macromedia you want this feature to be in the next version of ColdFusion. If so, go to www.macromedia.com/support/email/wishform/.

    Until we have that feature, there is a simple method for simulating an application or session startup. You can use a cfif to see if one of your application, session, or client variables has been defined yet. This is a simple example:

    <cfif not IsDefined("application.test")>
     <cfset application.test = "Not Set Yes">
    <cfif not IsDefined("session.test")>
     <cfset session.test = "Not Set Yet">
    The code utilizes the cfif tag (reference this column in the April 2004 issue), cfset tag (reference this column in February 2004), and the IsDefined function. The IsDefined function accepts one parameter, a string. The string is the name of the variable. If the variable is defined, the function returns true, otherwise it returns false. If the application variable is defined, you don't have to do anything. If it isn't, then you need to define it. The same concept applies to session variables. Generally, you only need to check for the existence of a single variable. If one is not defined, then it is safe to assume that none of them are defined.

    Session and application variables are called shared scope variables, because they are stored in shared memory space. You should always consider locking your shared scope variable access with the cflock tag. An in-depth explanation of locking is beyond the scope of this article. Read about the cflock tag in the live docs: http://livedocs.macromedia.com/coldfusion/6.1/htmldocs/tags-p71.htm# wp1100787. Versions of CF5 and prior had memory stability problems if you did not use locking. Read the Macromedia TechNote at www.macromedia.com/support/coldfusion/ts/documents/tn17882.htm. ColdFusion MX no longer has memory stability problems, but the best practices of locking remain relatively unchanged. You can find more information at www.macromedia.com/support/coldfusion/ts/documents/tn18235.htm.

    Client variables are stored on disk, either in a database, the registry, or as cookies on the client's browser. Since they are not stored in shared memory, they do not need to be locked.

    Application.cfm and OnRequestEnd.cfm
    You may now be saying, "So, Jeff, that cfapplication tag seems pretty powerful. And the method for creating application and session variables is simple, yet elegant. But, I don't want to have this code on every single page. Is there a simpler way?" Well, I'm glad you asked. Yes, there is a simpler way. ColdFusion has a reserve filename, "Application.cfm", which helps us set our application variables or session variables in one place.

    Application.cfm is a file that runs at the start of every request for a ColdFusion page. ColdFusion will search in the current directory, then the parent directory, and so-on, all the way up to the drive root until it finds a file called "Application.cfm". If it doesn't find one, then it continues processing normally. The Application.cfm file can be considered an implicit include, and if ColdFusion does find one, the code contained within Application.cfm will be executed (the same way that an included file is executed). That means the Application.cfm file is executed on every request for a ColdFusion page in that directory and below (provided none of the subdirectories has its own Application.cfm). This makes the Application.cfm ideal for things like the cfapplication tag, initializing application or session variables, and any other business logic you need to run at the beginning of every request.

    If the ColdFusion server finds an Application.cfm file it will search in the same directory for an "OnRequestEnd.cfm" file. Just like the Application.cfm, this file (if found) will execute on every page request. Unlike Application.cfm, the OnRequestEnd.cfm executes after the page is finished processing, not before. OnRequestEnd.cfm does not typically get as much use as the Application.cfm, but it's good to know it exists, as it can be useful for footers or application cleanup at the end of each request.

    When the Web started out, it wasn't being used for anything other than static content. As time went by people started using it for much more. ColdFusion's application framework represents a powerful mechanism for turning a simple Web site into a Web application. This article gave you the groundwork; now all that remains is for you to apply it to your development. Let me know how it goes.

  • More Stories By Jeffry Houser

    Jeffry is a technical entrepreneur with over 10 years of making the web work for you. Lately Jeffry has been cooped up in his cave building the first in a line of easy to use interface components for Flex Developers at www.flextras.com . He has a Computer Science degree from the days before business met the Internet and owns DotComIt, an Adobe Solutions Partner specializing in Rich Internet Applications. Jeffry is an Adobe Community Expert and produces The Flex Show, a podcast that includes expert interviews and screencast tutorials. Jeffry is also co-manager of the Hartford CT Adobe User Group, author of three ColdFusion books and over 30 articles, and has spoken at various events all over the US. In his spare time he is a musician, old school adventure game aficionado, and recording engineer. He also owns a Wii. You can read his blog at www.jeffryhouser.com, check out his podcast at www.theflexshow.com or check out his company at www.dot-com-it.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.

    @ThingsExpo Stories
    "Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of the 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to gre...
    The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and shared the must-have mindsets for removing complexity from the develop...
    In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
    "Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
    Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
    Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
    "Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    "IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
    In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
    22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
    "Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
    Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
    "MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
    "There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
    SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
    SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
    It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...