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

Encapsulating Session State Management

Encapsulating Session State Management

ColdFusion developers rely on session state management and the SESSION scope extensively. But as applications grow in complexity, so do the number of SESSION variables, and the risk of overwriting or misusing them. It need not be that way; with a little work (and ColdFusion Components), SESSION use can be clean, simple, and highly organized.

When Session Data Proliferates
First, an introduction. The Web is stateless. Or put in terms that actually mean something, every request on the Web stands on its own two feet. The data received by a form submission, for example, is only available in the receiving page and not to subsequent requests. Or, user credentials specified at login are not kept until logout. And similarly, items put in a shopping cart won't still be in the cart at checkout time.

But wait a minute, those statements can't be true, can they? After all, we've all put items in shopping carts and then checked out, and we've all logged in to sites that remembered us until logout, haven't we? If the Web is stateless, how is that data maintained? That's the job of session state management, a mechanism that creates the illusion of state in a stateless world.

Data to be maintained between requests is stored on the server, along with an id that designates the client that the data belongs to. That id is sent back and forth with each and every request, so that the server can associate the maintained data and give the illusion of persistent data. In ColdFusion all this is accomplished using SESSION variables. Developers simply refer to variables like #SESSION.Firstname# and ColdFusion takes care of all the details (setting and receiving session identifiers, maintaining the SESSION data, and ensuring that the correct data is used when referring to variables with the SESSION scope).

Okay, end of introduction.

So you need to track session information, great. The first thing you do is set SESSIONMANAGEMNT="yes" in your <CFAPPLICATION> tag (which makes a lot of sense; after all, you can't use the SESSION scope without having first instructed ColdFusion to enable that functionality. Once enabled you are free to save any data within SESSION. For example, a simple variable:

<CFSET SESSION.FirstName="Ben">

or a more complex data type:

<CFSET SESSION.cart=ArrayNew(1)>

or even queries:

<CFQUERY DATASOURCE="dsn"
NAME="SESSION.profile">
SELECT *
FROM Users
WHERE user_id = #FORM.user_id#
</CFQUERY>

There is no limit to what can be stored in the SESSION scope. That's a good thing, but it's also a liability. Why? Consider the following:

  • SESSION data is available all over your application. What's to stop you from accidentally setting the same SESSION variable defined elsewhere (in code that you may not have looked at recently)?
  • Unlike simple variables that are created and used in a single page, SESSION variables by their very nature are created and used all over your application. Which means that any time a change is made to how SESSION variables are used, you run the risk of breaking code that uses those variables.
  • The more you use the SESSION scope, the more memory ColdFusion needs to store that data, and as the number of connected users increases, so does that resource usage. Without paying attention to all the data being stored in SESSION, can you be sure that you are not wasting resources?

    This is just the tip of the iceberg. The key here is that because SESSION variables are so easy to create and use, their use can quickly get out of hand unless some semblance of structure is imposed.

    The Basics of Encapsulation
    The word encapsulation is one of those terms that means lots of different things and usually ends up being misused most of the time. But at its simplest, encapsulation is a technique by which applications are separated into parts so that code need not know the inner workings of things it doesn't need to know.

    For example, stored procedures are one of the best known forms of encapsulation. A stored procedure contains one or more database instructions in the form of SQL statements, but all that is hidden from the stored procedure user who simply makes a call to obtain data or to perform some other operation. What happens within the stored procedure is not important, what is important is that it does what it's supposed to do, it just works.

    ColdFusion Custom Tags (or rather, well-written ColdFusion Custom Tags) offer another form of encapsulation. A tag is invoked to perform an operation, the details of which are concealed within the tag.

    Encapsulation thus does several things:

  • Encapsulation simplifies the creation of client code: Be it a stored procedure, a Custom Tag, or a Java object, client code need not worry about the inner workings of what is being invoked, and can concentrate on the task at hand.
  • Encapsulation makes changes safe: Encapsulated objects, like stored procedures or Custom Tags, have defined input and output, and that is all the client code ever interacts with directly. This means that code within the encapsulated object is free to change, so long as the input and output stays the same. Database schema changing, for example? That can be buried within the stored procedure.
  • Encapsulation helps resource management: When all access to an entity, for example, a database, occurs via a single entry point, it becomes possible to very effectively manage reuse, caching, and more.

    I'm using the term encapsulation a little more loosely than most object-oriented developers would like, but having said that, this is indeed what encapsulation is all about. (Note: This idea was explained in detail in CFDJ, Volume 4, issue 10.)

    ColdFusion Components and Encapsulation
    ColdFusion Components (CFCs for short), first introduced in ColdFusion MX, are a way to create reusable objects in ColdFusion. Although not objects in the purest sense, they do provide basic object functionality wrapped within the simplicity that is uniquely CFML. (Note: ColdFusion Components were introduced in detail in a two-part column that appeared in CFDJ, Volume 4, issues 6 & 7.)

    Two of the most important aspects of CFCs is that they can store data internally, and they can persist. Let me explain. Within every CFC is a special scope named THIS. THIS contains some default data, but it can also be used to store data of your own. For example, the following method accepts two arguments (first and last name) and then saves them into the THIS scope:

    <CFFUNCTION NAME="SetName"
    OUTPUT="no">
    <CFARGUMENT NAME="NameFirst"
    TYPE="string"
    REQUIRED="yes">
    <CFARGUMENT NAME="NameLast"
    TYPE="string"
    REQUIRED="yes">
    <CFSET THIS.NameFirst=ARGUMENTS.NameFirst>
    <CFSET THIS.NameLast=ARGUMENTS.NameLast>
    </CFFUNCTION>

    To invoke this method you could use the following code (assuming the previous method was saved in a file named user.cfc):

    <CFINVOKE COMPONENT="user"
    METHOD="SetName"
    NAMEFIRST="Ben"
    NAMELAST="Forta">

    This next method returns a string made up of the saved first and last name:

    <CFFUNCTION NAME="GetName"
    RETURNTYPE="string"
    OUTPUT="no">
    <CFRETURN THIS.NameFirst & " " &
    THIS.NameLast>
    </CFFUNCTION>

    So, SetName saves the name and GetName retrieves it, so the following code should save my name and return it as a string:

    <CFINVOKE COMPONENT="user"
    METHOD="SetName"
    NAMEFIRST="Ben"
    NAMELAST="Forta">
    <CFINVOKE COMPONENT="user"
    METHOD="GetName"
    RETURNVARIABLE="FullName">

    If you were to execute this code, however, you would throw an error. The SetName call will work, but GetName will complain that THIS.NameFirst and THIS.NameLast do not exist. Why? After all, they were just set in SetName?

    The problem with the above invocation is that the user component is being invoked twice, two separate invocations that have nothing to do with each other. Each <CFINVOKE> loads the component, invokes the appropriate method, and then unloads the components. So when GetName is executed there is no NameFirst and NameLast in THIS; those were in the previously invoked instance.

    The solution? Persistence. Aside from being a type of file, a CFC is a ColdFusion data type, an object. <CFINVOKE>, as used above, loads the object, uses it, and then unloads it. But those steps can be separated. Look at this example:

    <CFOBJECT COMPONENT="user"
    NAME="userObj">
    <CFINVOKE COMPONENT="#userObj#"
    METHOD="SetName"
    NAMEFIRST="Ben"
    NAMELAST="Forta">

    Here the component is being loaded as an object (which it actually is). The <CFOBJECT> instantiates (creates an instance of) the user object, but does not invoke any method. Rather, it stores the object in a named variable. <CFINVOKE> then invokes the previously loaded object; notice that the value passed to COMPONENT is the object (as opposed to the name of the CFC). Once an object is loaded it can be used multiple times, and as it is the same object being used over and over, all invocations share the same object and thus the same internal THIS scope.

    Here's a corrected version of the code to set and get the user name:

    <CFOBJECT COMPONENT="user"
    NAME="userObj">
    <CFINVOKE COMPONENT="#userObj#"
    METHOD="SetName"
    NAMEFIRST="Ben"
    NAMELAST="Forta">
    <CFINVOKE COMPONENT="#userObj#"
    METHOD="GetName"
    RETURNVARIABLE="FullName">

    <CFOBJECT> instantiates the object, SetName stores the values into THIS, and GetName returns it (possibly to be displayed).

    This can also be accomplished using object style invocation. For example, the object instantiation could be performed using:

    <CFSET userObj=CreateObject("component","user")>

    and the GetName could be executed as:

    <CFSET FullName=userObj.GetName()>]

    or used directly for display as:

    #userObj.GetName()#

    Session Encapsulation
    So, components are objects and can persist. The examples thus far loaded the object as local variables (type VARIABLES, the default variable type). But other scopes may be used too. Components may be loaded into REQUEST, for example:

    <CFOBJECT COMPONENT="user" NAME="REQUEST.userObj">

    and components may even be loaded into persistent scopes like SESSION:

    <CFSET SESSION.user=CreateObject("component", "user")>

    Which brings us back to session state management. Instead of defining and accessing all sorts of SESSION variables throughout your application, you could define just one, an object (an instantiated ColdFusion Component). If your application uses user data you may want to create a user.cfc, which would contain all user information (including obtaining information from underlying databases). To check if a user has logged in you'd use code like this:

    <CFIF NOT IsDefined("SESSION.user")>
    ... redirect to login page ...
    </CFIF>

    The login page would authenticate the user (if needed) and then create an instance of the user object in the user's SESSION scope:

    <CFOBJECT COMPONENT="user" NAME="SESSION.user">

    You may then want to initialize the object so as to populate the internal THIS with any needed information (user name, color preferences, language choices, and so on). Perhaps you'd simply pass the user id to an initialization method immediately after object creation:

    <CFSET SESSION.user.Init(user_id)>

    Init() should probably return a true or false flag (indicating whether or not the initialization was successful), and within the CFC you'll probably want each method to ensure that Init() was called before begin executed, but that is all internal to the CFC.

    What about user logout? Simple; when a user logs out you'd kill SESSION. user like this:

    <CFSET StructDelete(SESSION, "user")>

    so that on a subsequent request the login and initialization process would restart.

    With user.cfc you can do anything, so perhaps you'd have methods like these:

    • ChangePassword
    • GetLanguage
    • GetFirstName
    • GetLastName
    • GetFullName
    • GetDisplayName
    • IsMember
    • IsAdmin
    As you need new methods, you'll simply add them to the component, and the client code (your ColdFusion code that uses the component) need know nothing of the internal object workings.

    And this goes beyond user processing. Consider a shopping cart example. Shopping carts are stored in SESSION variables, but instead of storing arrays or structures or arrays of structures of whatever in SESSION and accessing them directly, you'd create a cart component. To start shopping you'd create an instance of the cart:

    <CFOBJECT COMPONENT="cart" NAME="SESSION.cart">

    When an item is to be added you'd call the appropriate method:

    <CFINVOKE COMPONENT="#SESSION.cart#"
    METHOD="AddItem"
    ITEMID="#itemid#"
    QUANTITY="#FORM.qty#">

    Other methods would update or remove items, and perhaps a list method would return a query (a ColdFusion query created within the CFC using the QueryNew() function) for displaying or processing. There is no limit to what you can do within a CFC, and your CFC code can evolve and adapt independent of any calling code.

    Conclusion
    ColdFusion Components are objects. CFCs facilitate the encapsulation of data and logic, and they can be made to persist if needed. The combination of these two features makes CFCs perfect for managing session state. With minimal work the techniques described here can be used in any application, and doing so will both simplify and improve your code.

  • 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
    "Dice has been around for the last 20 years. We have been helping tech professionals find new jobs and career opportunities," explained Manish Dixit, VP of Product and Engineering at Dice, in this SYS-CON.tv interview at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
    More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
    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 and how we integrate our thinking to solve complicated problems. In his session at 19th Cloud Expo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and sh...
    In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. 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 sett...
    We are always online. We access our data, our finances, work, and various services on the Internet. But we live in a congested world of information in which the roads were built two decades ago. The quest for better, faster Internet routing has been around for a decade, but nobody solved this problem. We’ve seen band-aid approaches like CDNs that attack a niche's slice of static content part of the Internet, but that’s it. It does not address the dynamic services-based Internet of today. It does...
    The WebRTC Summit New York, to be held June 6-8, 2017, at the Javits Center in New York City, NY, announces that its Call for Papers is now 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 20th International Cloud Expo and @ThingsExpo. WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web ...
    20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, 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 strategy.
    WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web communications world. The 6th WebRTC Summit continues our tradition of delivering the latest and greatest presentations within the world of WebRTC. Topics include voice calling, video chat, P2P file sharing, and use cases that have already leveraged the power and convenience of WebRTC.
    "We're a cybersecurity firm that specializes in engineering security solutions both at the software and hardware level. Security cannot be an after-the-fact afterthought, which is what it's become," stated Richard Blech, Chief Executive Officer at Secure Channels, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
    The Internet of Things (IoT) promises to simplify and streamline our lives by automating routine tasks that distract us from our goals. This promise is based on the ubiquitous deployment of smart, connected devices that link everything from industrial control systems to automobiles to refrigerators. Unfortunately, comparatively few of the devices currently deployed have been developed with an eye toward security, and as the DDoS attacks of late October 2016 have demonstrated, this oversight can ...
    Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
    Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, will share examples from a wide range of industries – includin...
    We're entering the post-smartphone era, where wearable gadgets from watches and fitness bands to glasses and health aids will power the next technological revolution. With mass adoption of wearable devices comes a new data ecosystem that must be protected. Wearables open new pathways that facilitate the tracking, sharing and storing of consumers’ personal health, location and daily activity data. Consumers have some idea of the data these devices capture, but most don’t realize how revealing and...
    Unless your company can spend a lot of money on new technology, re-engineering your environment and hiring a comprehensive cybersecurity team, you will most likely move to the cloud or seek external service partnerships. In his session at 18th Cloud Expo, Darren Guccione, CEO of Keeper Security, revealed what you need to know when it comes to encryption in the cloud.
    "We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
    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...
    Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at 20th Cloud Expo, Ed Featherston, director/senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
    In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
    According to Forrester Research, every business will become either a digital predator or digital prey by 2020. To avoid demise, organizations must rapidly create new sources of value in their end-to-end customer experiences. True digital predators also must break down information and process silos and extend digital transformation initiatives to empower employees with the digital resources needed to win, serve, and retain customers.
    "Once customers get a year into their IoT deployments, they start to realize that they may have been shortsighted in the ways they built out their deployment and the key thing I see a lot of people looking at is - how can I take equipment data, pull it back in an IoT solution and show it in a dashboard," stated Dave McCarthy, Director of Products at Bsquare Corporation, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.