|By Charlie Arehart||
|January 31, 2003 12:00 AM EST||
There are a lot of powerful new integration points between CFMX and Java, but one that might benefit a lot of people - even those who don't know how to program in Java - is the ability to leverage servlet filters in CFMX.
A filter is a Java program that can be used to execute before and/or after your CF template. More than just running some code in advance, a filter can also manipulate the request (the HTTP stream) that is calling your template, and can change how, or even if, your template is run, or cause some other template or code to run first. It can also manipulate the output (the HTTP response) that your template generates.
ColdFusion MX can run servlet filters. You don't need to write them because some have already been written for servlet and JSP developers. Because ColdFusion MX runs atop a J2EE server, we can leverage these or even write our own filters if we want to.
In this article, I'll show you where to find some example filters and how to implement them in CFMX. You don't need to understand Java to use them. By the way, they work in both the Enterprise and Pro (as well as developer and trial) editions of CFMX, and also with the built-in Web server in CFMX and external Web servers like IIS and Apache.
How Do Filters Compare to Application.cfm?
Filters may sound very similar to the way Application.cfm (and OnRequestEnd.cfm) work. But a filter has many added benefits and is really quite different from those two traditional mechanisms in CF. Before getting into the details of filters, it may help to first contrast them to those more traditional approaches.
Most will know that Application.cfm and OnRequestEnd.cfm are templates that run before (and after, in the case of OnRequestEnd.cfm) a ColdFusion template is executed. They provide a means to effect some kind of pre-or post-processing in order to augment your template.
Some use them to add a test (such as security) before a template runs, or to create some data structure (perhaps persisted in the application scope) to be shared by many templates. Some even use them for creating headers (and footers), though that may get complicated if you have a template that should run without the headers or footers.
Some Challenges with Application.cfm/OnRequestEnd.cfm
One problem with the traditional CF approach is that there's no way to stop these two files from running for any one template, as might be desired when trying to use them for headers and footers. (Of course, using them for headers and footers may be an arguable approach, but it does point up a limitation with them.) Any time you run a CF template, CF looks to run any existing Application.cfm in the current or a parent directory, whichever it finds first. And if there's an OnRequestEnd.cfm in the same directory as the Application.cfm that's run, that will be executed at the conclusion of the named template.
You can't tell CF to not run these files if they exist. Some of the other challenges are:
So why should they get excited about servlet filters? What do they really add?
Where Filters Augment Traditional CF Approaches
Filters work differently from the traditional approach of automatically running Application.cfm and OnRequestEnd.cfm. For one thing, you have much greater control of when a filter is run. Through some configuration files built into CFMX, which we will see later, you map filters to a given URL pattern, so that they can be made to apply to:
- A single template
- All templates in a given directory and subdirectories
- All templates of a given file type
- All templates on the entire server
More important, because these are added declaratively through configuration files (rather than controlled by code in the template directories) you can also:
- Designate multiple URL patterns for a given filter
- Designate multiple filters to a given pattern
- Add/remove/modify filters without the templates knowing about it
- Apply changes to a filter across several applications
It's true that CF developers can do some of these things themselves in Application.cfm processing, but remember that they may already be written as servlet filters, thus saving you the development effort. Also, remember the greater flexibility in mapping filters to URLs.
What could a response (output) filter do? Again, this is just a short list of creative solutions that do exist or could be created to process the output of a template before returning it to the user:
- Log page execution time
- Localization (targeting output to a locale)
- Image conversion
- XML transformations of XML output
- Data compression (gzip)
Where Can I Find Them?
As for where you can find these already written, there are a few places including jsptags.com and servletsuite.com. There are surely more, but the latter has quite a few that might interest CFers, including:
Profiler filter (track execution times)
IP filter (access restriction, load balancing)
The Power of a Compression Filter
That last item in the list, a compression filter, may be the most compelling one for many and, I'll give a specific example of one as a demonstration of how all this works. A compression filter, also often called a Zip or gzip filter, is a tool that compresses the output of a Web page so that it generally takes up far less space when being sent from the server to the browser. The browser can then decompress the page and render it as usual to the end user.
CF pages are notorious for having excessive white space, so a compression filter can be a big win for us. The good news is that most browsers, even relatively old ones, can support decompression. A compression filter will determine if a browser can support compression by checking the HTTP header called accept-encoding (or in CF, you could test it with cgi.http_accept_encoding) before trying to compress the page. A smart one might also balance the size of the page being processed before trying to compress it, since compression does cost some CPU cycles on both the server (to compress) and the client (to decompress) page.
Still, for all but the most trivial page, compression is generally a good thing, and it's rather easily tested to confirm the savings. In some testing I did, it resulted in a 4:1 reduction in bandwidth (size of pages downloaded to the browser). For sites that pay for their bandwidth utilization (someone is always paying for it), or just for the speed improvement of sending "lighter" pages to the browser, compression is valuable.
(It's worth noting that both Apache and IIS offer their own forms of compression that, if implemented properly, will generally suffice to provide the benefits that compression can bring. But if they're not set up, or not set up properly, then a filter in CFMX may be a good way to go. In fact, I wonder if in the future Macromedia may build one in and make it more simply enabled via an Administrator setting. Until then, it's a good example of a filter.)
How to Implement a Filter in Three Easy Steps
It's incredibly easy to implement a filter. If you visit any of the pages mentioned here, you'll find explanations of the filters, the downloadable files, how to configure them, and maybe an example that might be written as a JSP page. Most don't even show that, because there's nothing necessarily specific about using a filter with either CF or a JSP page, for instance. You just associate the filter with a given URL, and the filter doesn't care what kind of page it's processing before or after.
The only clue that the filter is written in Java is that the downloadable files will likely refer to a JAR (Java Archive). But all you need to know is where to put that file and how to set up CFMX to map the filter to a URL. That's really all there is to it. Indeed, the explanations on the page will often be very similar if not identical to what you need in CFMX. There are just three simple steps. I'll walk you through implementing that gzip/compression filter.
Upon visiting the page that holds the filter, such as the last one for the gzip filter mentioned above at www.servletsuite.com/servlets/ipflt.htm, you'll find a link to the JAR file that needs to be downloaded and placed into the cfusionmx\wwwroot\WEB-INF\lib directory. It doesn't matter if you use another Web server or store your CF templates somewhere other than the cfusionmx\wwwroot. That directory will still exist, and under it you will find the WEB-INF\lib subdirectory. Place the file there. This is the location in which J2EE servers (like that underlying CFMX) expect to find Java programs like filters, when they are packaged as JAR files. (If you happened to get a filter or servlet that was just a "class" file, rather than a JAR, it would be placed in the cfusionmx\wwwroot\WEB-INF\classes directory.)
As the page showing the downloadable filter may also indicate, the next step is to modify the web.xml file to define a pointer and map to the filter. Again, this file does exist in CFMX, specifically in the cfusionmx\wwwroot\WEB-INF. The directions will likely indicate just the XML that you need to add to the web.xml file. In the case of the compression filter, it would be:
Note that in the next to last line, we're indicating that this filter should apply against all files of type "cfm", and since we don't say otherwise, it means all such files in all directories that are run under CFMX. You could create additional filter-mapping entries to list other URL mappings. To just control files in a "test" directory under your webroot, the pattern could be "/test/*.cfm" or simply "/test/*".
Of course, as when modifying any of the XML files in the CFMX configuration, be very careful. It may even be wise to save a backup of the file before editing it so that you can recover in case the server fails to start, etc.
The last step is to restart the server. CF will not detect the filter unless the server is restarted. It may not seem obvious that this should be so, but it actually looks for and preprocesses any filters at startup.
This has been a pretty quick introduction to servlet filters. You'll notice we didn't look at a single line of Java code. We're not interested here in creating filters, just in using them. There are plenty of resources for learning more about creating them - though there's not too much more you need to know about using them. We've run out of room to cover any further details, but if you're interested in more on this subject, including a few other tips that may help you as you explore them, take a look at the slides from my one-hour user group presentation, "Augmenting Application.cfm with Filters," available at my site at www.systemanage.com/presentations.
17th Cloud Expo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, 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. Meanwhile, 94% of enterprises are using some form of XaaS – software, platform, and infrastructure as a service.
Sep. 5, 2015 12:00 PM EDT Reads: 1,628
While many app developers are comfortable building apps for the smartphone, there is a whole new world out there. In his session at @ThingsExpo, Narayan Sainaney, Co-founder and CTO of Mojio, will discuss how the business case for connected car apps is growing and, with open platform companies having already done the heavy lifting, there really is no barrier to entry.
Sep. 5, 2015 11:45 AM EDT Reads: 256
SYS-CON Events announced today that the "Second Containers & Microservices Expo" will take place November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities.
Sep. 5, 2015 11:45 AM EDT Reads: 680
Manufacturing connected IoT versions of traditional products requires more than multiple deep technology skills. It also requires a shift in mindset, to realize that connected, sensor-enabled “things” act more like services than what we usually think of as products. In his session at @ThingsExpo, David Friedman, CEO and co-founder of Ayla Networks, will discuss how when sensors start generating detailed real-world data about products and how they’re being used, smart manufacturers can use the data to create additional revenue streams, such as improved warranties or premium features. Or slash...
Sep. 5, 2015 11:00 AM EDT Reads: 145
The Internet of Things is in the early stages of mainstream deployment but it promises to unlock value and rapidly transform how organizations manage, operationalize, and monetize their assets. IoT is a complex structure of hardware, sensors, applications, analytics and devices that need to be able to communicate geographically and across all functions. Once the data is collected from numerous endpoints, the challenge then becomes converting it into actionable insight.
Sep. 5, 2015 11:00 AM EDT Reads: 175
Contrary to mainstream media attention, the multiple possibilities of how consumer IoT will transform our everyday lives aren’t the only angle of this headline-gaining trend. There’s a huge opportunity for “industrial IoT” and “Smart Cities” to impact the world in the same capacity – especially during critical situations. For example, a community water dam that needs to release water can leverage embedded critical communications logic to alert the appropriate individuals, on the right device, as soon as they are needed to take action.
Sep. 5, 2015 10:45 AM EDT Reads: 205
With the Apple Watch making its way onto wrists all over the world, it’s only a matter of time before it becomes a staple in the workplace. In fact, Forrester reported that 68 percent of technology and business decision-makers characterize wearables as a top priority for 2015. Recognizing their business value early on, FinancialForce.com was the first to bring ERP to wearables, helping streamline communication across front and back office functions. In his session at @ThingsExpo, Kevin Roberts, GM of Platform at FinancialForce.com, will discuss the value of business applications on wearable ...
Sep. 5, 2015 10:45 AM EDT Reads: 178
Akana has announced the availability of the new Akana Healthcare Solution. The API-driven solution helps healthcare organizations accelerate their transition to being secure, digitally interoperable businesses. It leverages the Health Level Seven International Fast Healthcare Interoperability Resources (HL7 FHIR) standard to enable broader business use of medical data. Akana developed the Healthcare Solution in response to healthcare businesses that want to increase electronic, multi-device access to health records while reducing operating costs and complying with government regulations.
Sep. 5, 2015 10:30 AM EDT Reads: 365
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo in Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th 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 an...
Sep. 5, 2015 10:15 AM EDT Reads: 2,081
Containers are not new, but renewed commitments to performance, flexibility, and agility have propelled them to the top of the agenda today. By working without the need for virtualization and its overhead, containers are seen as the perfect way to deploy apps and services across multiple clouds. Containers can handle anything from file types to operating systems and services, including microservices. What are microservices? Unlike what the name implies, microservices are not necessarily small, but are focused on specific tasks. The ability for developers to deploy multiple containers – thous...
Sep. 5, 2015 10:00 AM EDT Reads: 257
As more intelligent IoT applications shift into gear, they’re merging into the ever-increasing traffic flow of the Internet. It won’t be long before we experience bottlenecks, as IoT traffic peaks during rush hours. Organizations that are unprepared will find themselves by the side of the road unable to cross back into the fast lane. As billions of new devices begin to communicate and exchange data – will your infrastructure be scalable enough to handle this new interconnected world?
Sep. 5, 2015 08:30 AM EDT Reads: 316
Consumer IoT applications provide data about the user that just doesn’t exist in traditional PC or mobile web applications. This rich data, or “context,” enables the highly personalized consumer experiences that characterize many consumer IoT apps. This same data is also providing brands with unprecedented insight into how their connected products are being used, while, at the same time, powering highly targeted engagement and marketing opportunities. In his session at @ThingsExpo, Nathan Treloar, President and COO of Bebaio, will explore examples of brands transforming their businesses by t...
Sep. 5, 2015 08:00 AM EDT Reads: 335
Through WebRTC, audio and video communications are being embedded more easily than ever into applications, helping carriers, enterprises and independent software vendors deliver greater functionality to their end users. With today’s business world increasingly focused on outcomes, users’ growing calls for ease of use, and businesses craving smarter, tighter integration, what’s the next step in delivering a richer, more immersive experience? That richer, more fully integrated experience comes about through a Communications Platform as a Service which allows for messaging, screen sharing, video...
Sep. 5, 2015 08:00 AM EDT Reads: 781
The 3rd International WebRTC Summit, to be held Nov. 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA, 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 15th International Cloud Expo, 6th International Big Data Expo, 3rd International DevOps Summit and 2nd Internet of @ThingsExpo. WebRTC (Web-based Real-Time Communication) is an open source project supported by Google, Mozilla and Opera that aims to enable bro...
Sep. 5, 2015 07:15 AM EDT Reads: 1,667
SYS-CON Events announced today the Containers & Microservices Bootcamp, being held November 3-4, 2015, in conjunction with 17th Cloud Expo, @ThingsExpo, and @DevOpsSummit at the Santa Clara Convention Center in Santa Clara, CA. This is your chance to get started with the latest technology in the industry. Combined with real-world scenarios and use cases, the Containers and Microservices Bootcamp, led by Janakiram MSV, a Microsoft Regional Director, will include presentations as well as hands-on demos and comprehensive walkthroughs.
Sep. 5, 2015 07:00 AM EDT Reads: 466
WebRTC has had a real tough three or four years, and so have those working with it. Only a few short years ago, the development world were excited about WebRTC and proclaiming how awesome it was. You might have played with the technology a couple of years ago, only to find the extra infrastructure requirements were painful to implement and poorly documented. This probably left a bitter taste in your mouth, especially when things went wrong.
Sep. 5, 2015 07:00 AM EDT Reads: 527
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!
Sep. 5, 2015 06:30 AM EDT Reads: 1,740
In his session at @ThingsExpo, Lee Williams, a producer of the first smartphones and tablets, will talk about how he is now applying his experience in mobile technology to the design and development of the next generation of Environmental and Sustainability Services at ETwater. He will explain how M2M controllers work through wirelessly connected remote controls; and specifically delve into a retrofit option that reverse-engineers control codes of existing conventional controller systems so they don't have to be replaced and are instantly converted to become smart, connected devices.
Sep. 5, 2015 05:00 AM EDT Reads: 306
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
Sep. 5, 2015 01:30 AM EDT Reads: 1,015
All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades. With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo, November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be.
Sep. 5, 2015 01:00 AM EDT Reads: 275