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
"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 ...