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

Using Gateways PART 2

The basics

Part 1 in this series (CFDJ, Vol. 7, issue 5) discussed the options in the ColdFusion Administrator for configuring the event gateway facility in ColdFusion MX 7 and how to register new event gateway types.

There was little in the way of explaining how to use event gateways, so in this article we'll explore the basics of using event gateways through two examples: the code from the previous article and another of the out-of-the-box event gateway types, the CFML asynchronous event gateway type. These two gateway types represent the two fundamental varieties: the types that respond to events external to a ColdFusion application and the types that respond to events generated within a ColdFusion application.

Event gateways represent a new kind of service architecture for ColdFusion that is composed of a number of logical groups, each with its own intricacies. This article glosses over much of the deeper details with the intent of getting you up and running without bogging you down. Not to worry though, the finer details ignored now will be covered in greater detail in a later article.

A rough overview of the choreography of gateways can be seen in the ColdFusion MX 7 product documentation (Developing ColdFusion MX Applications, Using Event Gateways, About event gateways, How event gateway applications work). Many of the framed pieces in this diagram are identified with common event gateway jargon discussed in Part 1. [http://livedocs.macromedia.com/coldfusion/7/ htmldocs/images/gatewayb.jpg]

The two discrete pieces we're going to discuss in this article are the listener CFCs and CFM Pages (the calling logic being either a CFML template or a ColdFusion Component).

CFML Code for Gateways
To create a gateway instance you need a gateway type, a configuration file (which is optional in some cases) and a listener CFC. ColdFusion MX 7 comes with seven gateway types to start you off, one of which, the DirectoryWatcher type, was used in the previous article to verify the instructions for creating a gateway instance. Since the sample code was for an event gateway that responded to external OS level events, it had only a listener CFC written for it, which is a good place to begin.

Listener CFCs
Developers familiar with frameworks in other languages will recognize the role that the methods in a listener CFC fulfill - the event handler. Similar to a class implementing a component or control delegate in the .NET Framework or a Java bean event listener in Java, the listener CFC is the chunk of code that is the implementation-specific part of the more generic problem domain as defined by the gateway type.

While the gateway type defines the method names, the signature always remains the same (with the obvious exception of the method name itself): a public method with one argument, a structure, which may return a string. (Note: Signature is a term used to indicate a function's or a method's definition, its name, the names and data types of its arguments, and data type of the returned value [http://en.wikipedia.org/wiki/Signature_%28Computer_Science%29].)

Event Handling Methods
The one method argument is called the CFEvent and contains information about the gateway instance, the default listener CFC that the gateway instance will use, and a structure containing any data elements sent by the method's calling logic. These data elements can be populated by the Java code of the gateway type as well as the CFML code invoking the gateway instance.

The Members of CFEvent
Each event handler method receives a single structure, the CFEvent argument. This structure contains seven members by default that are almost solely for informational purposes. They are listed in Table 1 and in the ColdFusion product documentation (CFML Reference, ColdFusion MX Event Gateway Reference, CFML CFEvent structure).

Reviewing the Previous Sample
Looking at the code from Part 1 (available at: [http://gemsres.com/story/may05/86134/source.html]), we find two files, CCOJASDirectoryWatcher.cfg (the configuration file) and CCOJASDirectoryWatcher.cfc (the listener CFC), which were used to create the gateway instance, CCOJASDirectoryWatcher.

Within this component we see three methods: onAdd, onDelete, and onChange. These methods are defined by the DirectoryWatcher gateway type (Developing ColdFusion MX Applications, Using Event Gateways, Using the example event gateways and gateway applications). These methods are the event handlers for the DirectoryWatcher gateway instance and none of them are required. If a listener CFC does not implement one of these event handling methods, the gateway instance does not attempt to make a call to the method. This means that the listener CFC needs to implement only what is germane to the problem domain and nothing more.

The CFEvent's data Member
In the case of this example, all three event handling methods were implemented and, as was demonstrated in Part 1 ("Cold Cup o' Joe - Another Shot: Gateways to Fun, Putting It All Together"), a log file was updated each time a file was added to, changed, and deleted from the watched directory. What is more interesting now is not just the execution of the gateway instance but the variables that get passed to the event handling methods.

Referring to CCOJASDirectoryWatcher.cfc from Part 1, you'll see that the first functional line of each method (lines 5, 12, and 19) pull out a structure called data from each method's CFEvent argument. This contains data about each OS level event that the DirectoryWatcher was monitoring for. This structure contains three members, identified in the ColdFusion product documentation (Developing ColdFusion MX Applications, Using Event Gateways, Using the example event gateways and gateway applications, Example event gateway, CFC methods) and shown in Table 2.

More Stories By Guy Rish

Guy Rish is a ColdFusion and .NET developer at Vente as well as President at Gestaltech. He is an active developer and writer for various languages and technologies, and has contributed work in books on ColdFusion MX, Flash MX, and Dreamweaver MX. He blogs at ccoj.coldfusionjournal.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
"We've been engaging with a lot of customers including Panasonic, we've been involved with Cisco and now we're working with the U.S. government - the Department of Homeland Security," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held June 6-8, 2017, at the Javits Center in New York City, NY.
"We provide IoT solutions. We provide the most compatible solutions for many applications. Our solutions are industry agnostic and also protocol agnostic," explained Richard Han, Head of Sales and Marketing and Engineering at Systena America, in this SYS-CON.tv interview at @ThingsExpo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that Calligo, an innovative cloud service provider offering mid-sized companies the highest levels of data privacy and security, has been named "Bronze Sponsor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Calligo offers unparalleled application performance guarantees, commercial flexibility and a personalised support service from its globally located cloud plat...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
"The Striim platform is a full end-to-end streaming integration and analytics platform that is middleware that covers a lot of different use cases," explained Steve Wilkes, Founder and CTO at Striim, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
SYS-CON Events announced today that Datera, that offers a radically new data management architecture, has been named "Exhibitor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Datera is transforming the traditional datacenter model through modern cloud simplicity. The technology industry is at another major inflection point. The rise of mobile, the Internet of Things, data storage and Big...
"We are focused on SAP running in the clouds, to make this super easy because we believe in the tremendous value of those powerful worlds - SAP and the cloud," explained Frank Stienhans, CTO of Ocean9, Inc., in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
DX World EXPO, LLC., a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"MobiDev is a Ukraine-based software development company. We do mobile development, and we're specialists in that. But we do full stack software development for entrepreneurs, for emerging companies, and for enterprise ventures," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
While the focus and objectives of IoT initiatives are many and diverse, they all share a few common attributes, and one of those is the network. Commonly, that network includes the Internet, over which there isn't any real control for performance and availability. Or is there? The current state of the art for Big Data analytics, as applied to network telemetry, offers new opportunities for improving and assuring operational integrity. In his session at @ThingsExpo, Jim Frey, Vice President of S...
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
In his opening keynote at 20th Cloud Expo, Michael Maximilien, Research Scientist, Architect, and Engineer at IBM, discussed the full potential of the cloud and social data requires artificial intelligence. By mixing Cloud Foundry and the rich set of Watson services, IBM's Bluemix is the best cloud operating system for enterprises today, providing rapid development and deployment of applications that can take advantage of the rich catalog of Watson services to help drive insights from the vast t...
SYS-CON Events announced today that EnterpriseTech has been named “Media Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. EnterpriseTech is a professional resource for news and intelligence covering the migration of high-end technologies into the enterprise and business-IT industry, with a special focus on high-tech solutions in new product development, workload management, increased effic...
SYS-CON Events announced today that Massive Networks, that helps your business operate seamlessly with fast, reliable, and secure internet and network solutions, has been named "Exhibitor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. As a premier telecommunications provider, Massive Networks is headquartered out of Louisville, Colorado. With years of experience under their belt, their team of...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
SYS-CON Events announced today that Cloudistics, an on-premises cloud computing company, has been named “Bronze Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Cloudistics delivers a complete public cloud experience with composable on-premises infrastructures to medium and large enterprises. Its software-defined technology natively converges network, storage, compute, virtualization, and ...
SYS-CON Events announced today that CHEETAH Training & Innovation will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CHEETAH Training & Innovation is a cloud consulting and IT training firm specializing in improving clients cloud strategies and infrastructures for medium to large companies.
SYS-CON Events announced today that Datanami has been named “Media Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Datanami is a communication channel dedicated to providing insight, analysis and up-to-the-minute information about emerging trends and solutions in Big Data. The publication sheds light on all cutting-edge technologies including networking, storage and applications, and thei...
The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...