Click here to close now.

Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Maureen O'Gara, Nancy Y. Nee, Tad Anderson, Daniel Kaar

Related Topics: ColdFusion

ColdFusion: Article

Fun with Filters in CFMX

Fun with Filters in CFMX

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:

  • You can't apply them selectively to only some templates in a directory
  • You can't run more than one. As soon as CF finds the closest one (in the current or an ancestor directory), it runs that one and looks for no more
  • You can't have just an OnRequestEnd.cfm. It only runs if there is a corresponding Application.cfm in the same directory
  • If you do a CFABORT, any OnRequestEnd.cfm is not executed
  • They apply only to CF templates, not to HTML pages or indeed to JSPs or servlets running alongside your CF templates (which is now possible in CFMX, though JSPs can run in CFMX Enterprise only) Now, many developers haven't worried too much about these limitations. Heck, some never even knew about OnRequestEnd.cfm. It came out in 4.01 with little fanfare. See my February 2000 article, "Hidden Gems in 4.0.1 - What You Might Have Missed," at www.sys-con.com/coldfusion/article.cfm?id=81 for more such surprises.

    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
    Try that with Application.cfm! They can also apply not just to requests for CF templates but also even HTML or image files, for instance.

    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
    Remember that filters can either process the incoming request or the outgoing response (HTML result, typically) of a CF template (or servlet or JSP if running under CFMX). What kinds of things could a request (input) filter do? To name a few:
  • Log and audit visits
  • Block execution of a page for a given time period (perhaps during a maintenance period)
  • Block visitors from given domains
  • Trigger events when a resource is accessed
  • Cache/reuse a page's results
  • Modify the input request before processing by CF
  • Test for/handle cross-browser scripting attempts
  • Modify request character encoding

    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
    • Encryption
    • Data compression (gzip)
    I mentioned that filters have been written and used by JSP and servlet developers for some time. There are public repositories of them that address all sorts of useful programming solutions, some of which are just as valuable to CF developers.

    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:

    Cache filter
    www.servletsuite.com/servlets/cacheflt.htm
    Billing filter
    www.servletsuite.com/servlets/billflt.htm
    Profiler filter (track execution times)
    www.servletsuite.com/servlets/profflt.htm
    IP filter (access restriction, load balancing)
    www.servletsuite.com/servlets/ipflt.htm
    Zip/Compression filter
    www.servletsuite.com/servlets/gzipflt.htm

    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.

  • Step 1: Download the filter (JAR file):
    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.)

  • Step 2: Implement the filter mapping (XML configuration):
    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:

    <filter>
    <filter-name>GZIPFilter</filter-name>
    <filter-class>com.cj.gzipflt.GzipFilter</filter-class>
    </filter>

    <filter-mapping>
    <filter-name>GZIPFilter</filter-name>
    <url-pattern>*.cfm</url-pattern>
    </filter-mapping>

    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.

  • Step 3: Restart the CFMX server:
    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.

    Conclusion
    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.

  • More Stories By Charlie Arehart

    A veteran ColdFusion developer since 1997, Charlie Arehart is a long-time contributor to the community and a recognized Adobe Community Expert. He's a certified Advanced CF Developer and Instructor for CF 4/5/6/7 and served as tech editor of CFDJ until 2003. Now an independent contractor (carehart.org) living in Alpharetta, GA, Charlie provides high-level troubleshooting/tuning assistance and training/mentoring for CF teams. He helps run the Online ColdFusion Meetup (coldfusionmeetup.com, an online CF user group), is a contributor to the CF8 WACK books by Ben Forta, and is frequently invited to speak at developer conferences and user groups worldwide.

    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
    Health care systems across the globe are under enormous strain, as facilities reach capacity and costs continue to rise. M2M and the Internet of Things have the potential to transform the industry through connected health solutions that can make care more efficient while reducing costs. In fact, Vodafone's annual M2M Barometer Report forecasts M2M applications rising to 57 percent in health care and life sciences by 2016. Lively is one of Vodafone's health care partners, whose solutions enable older adults to live independent lives while staying connected to loved ones. M2M will continue to gr...
    How is unified communications transforming the way businesses operate? In his session at WebRTC Summit, Arvind Rangarajan, Director of Product Marketing at BroadSoft, will discuss how to extend unified communications experience outside the enterprise through WebRTC. He will also review use cases across different industry verticals. Arvind Rangarajan is Director, Product Marketing at BroadSoft. He has over 19 years of experience in the telecommunications industry in various roles such as Software Development, Product Management and Product Marketing, applied across Wireless, Unified Communic...
    Dave will share his insights on how Internet of Things for Enterprises are transforming and making more productive and efficient operations and maintenance (O&M) procedures in the cleantech industry and beyond. Speaker Bio: Dave Landa is chief operating officer of Cybozu Corp (kintone US). Based in the San Francisco Bay Area, Dave has been on the forefront of the Cloud revolution driving strategic business development on the executive teams of multiple leading Software as a Services (SaaS) application providers dating back to 2004. Cybozu's kintone.com is a leading global BYOA (Build Your O...
    SYS-CON Events announced today that Vicom Computer Services, Inc., a provider of technology and service solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. They are located at booth #427. Vicom Computer Services, Inc. is a progressive leader in the technology industry for over 30 years. Headquartered in the NY Metropolitan area. Vicom provides products and services based on today’s requirements around Unified Networks, Cloud Computing strategies, Virtualization around Software defined Data Ce...
    What exactly is a cognitive application? In her session at 16th Cloud Expo, Ashley Hathaway, Product Manager at IBM Watson, will look at the services being offered by the IBM Watson Developer Cloud and what that means for developers and Big Data. She'll explore how IBM Watson and its partnerships will continue to grow and help define what it means to be a cognitive service, as well as take a look at the offerings on Bluemix. She will also check out how Watson and the Alchemy API team up to offer disruptive APIs to developers.
    The IoT Bootcamp is coming to Cloud Expo | @ThingsExpo on June 9-10 at the Javits Center in New York. Instructor. Registration is now available at http://iotbootcamp.sys-con.com/ Instructor Janakiram MSV previously taught the famously successful Multi-Cloud Bootcamp at Cloud Expo | @ThingsExpo in November in Santa Clara. Now he is expanding the focus to Janakiram is the founder and CTO of Get Cloud Ready Consulting, a niche Cloud Migration and Cloud Operations firm that recently got acquired by Aditi Technologies. He is a Microsoft Regional Director for Hyderabad, India, and one of the f...
    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!
    SYS-CON Events announced today that SoftLayer, an IBM company, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place June 9-11, 2015 at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place November 3–5, 2015 at the Santa Clara Convention Center in Santa Clara, CA. SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from ...
    SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborate. Cisco and our partners are building the platform for the Internet of Everything by connecting the...
    SYS-CON Events announced today that Liaison Technologies, a leading provider of data management and integration cloud services and solutions, has been named "Silver Sponsor" of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York, NY. Liaison Technologies is a recognized market leader in providing cloud-enabled data integration and data management solutions to break down complex information barriers, enabling enterprises to make smarter decisions, faster.
    SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
    SYS-CON Events announced today that Ciqada will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Ciqada™ makes it easy to connect your products to the Internet. By integrating key components - hardware, servers, dashboards, and mobile apps - into an easy-to-use, configurable system, your products can quickly and securely join the internet of things. With remote monitoring, control, and alert messaging capability, you will meet your customers' needs of tomorrow - today! Ciqada. Let your products take flight. For more inform...
    SYS-CON Events announced today that ProfitBricks, the provider of painless cloud infrastructure, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY., and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. ProfitBricks is the IaaS provider that offers a painless cloud experience for all IT users, with no learning curve. ProfitBricks boasts flexible cloud servers and networking, an integrated Data Center Designer tool f...
    SYS-CON Events announced today that GENBAND, a leading developer of real time communications software solutions, has been named “Silver Sponsor” of SYS-CON's WebRTC Summit, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. The GENBAND team will be on hand to demonstrate their newest product, Kandy. Kandy is a communications Platform-as-a-Service (PaaS) that enables companies to seamlessly integrate more human communications into their Web and mobile applications - creating more engaging experiences for their customers and boosting collaboration and productiv...
    SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.
    SYS-CON Events announced today that Open Data Centers (ODC), a carrier-neutral colocation provider, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. Open Data Centers is a carrier-neutral data center operator in New Jersey and New York City offering alternative connectivity options for carriers, service providers and enterprise customers.
    SYS-CON Events announced today that On the Avenue Marketing Group, a sales and marketing firm that utilizes events to market and sell products to consumers, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. On the Avenue Marketing Group (OTA) is a sales and marketing firm that utilizes events to market and sell products to consumers. On behalf of our clients, we attend thousands of fairs, festivals, expos, concerts, conferences, and sporting events annually, helping them reach millions of individuals ...
    SYS-CON Events announced today that BroadSoft, the leading global provider of Unified Communications and Collaboration (UCC) services to operators worldwide, has been named “Gold Sponsor” of SYS-CON's WebRTC Summit, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. BroadSoft is the leading provider of software and services that enable mobile, fixed-line and cable service providers to offer Unified Communications over their Internet Protocol networks. The Company’s core communications platform enables the delivery of a range of enterprise and consumer calling...
    SYS-CON Events announced today that ActiveState, the leading independent Cloud Foundry and Docker-based PaaS provider, has been named “Silver Sponsor” of SYS-CON's DevOps Summit New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. ActiveState believes that enterprises gain a competitive advantage when they are able to quickly create, deploy and efficiently manage software solutions that immediately create business value, but they face many challenges that prevent them from doing so. The Company is uniquely positioned to help address these challenges thro...
    SYS-CON Events announced today that Vitria Technology, Inc. will exhibit at SYS-CON’s @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Vitria will showcase the company’s new IoT Analytics Platform through live demonstrations at booth #330. Vitria’s IoT Analytics Platform, fully integrated and powered by an operational intelligence engine, enables customers to rapidly build and operationalize advanced analytics to deliver timely business outcomes for use cases across the industrial, enterprise, and consumer segments.