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

The XPath Factor

XML and XPath

It's 3:00 P.M. on a sunny Saturday afternoon. The birds are chirping, the leaves are blowing, and you can hear the lake waters breaking on its rocky shores. The sounds of a baseball game randomly crack in the distance, and the roar of competition erupts on the basketball courts nearby.

My burgers are just getting medium-well as my wife is returning from a little potty walk with the dog. Our blanket is set and our picnic looks like it will be wonderful. Who knew a Web geek like me could pull off such a seemingly perfect day? Interestingly enough, I owe much of its success to XML and XPath.

XPath is to XML what SQL is to databases. Databases would be quite pointless if you could not query information out of them, and the same holds true for XML documents. XPath is a language for finding information in XML documents. XPath provides access to all of the elements and attributes of an XML document. It became a World Wide Web Consortium (W3C) recommendation on November 16, 1999 and since then it has become a huge part of the XML world. It is a major element of the W3C's XSLT standard, and both XQuery and XPointer are built upon XPath expressions.

An expression is XPath's primary construct, a string that, in its basic form, resembles a file path. True XPath engines examine the expression and return a node-set (more on nodes later), Boolean, number, or string from the XML document. ColdFusion's implementation of XPath only supports the node-set return type. For more complete XPath support you can use one of the many Java libraries available on the Internet.

XML has reared its head all over the Web, and with XPath being such a cornerstone of the XML world, a solid understanding of it is crucial. XML can be found any place where you need to provide or acquire data from a third-party vendor, client, application, or server. Web services, WDDX packets, and RSS feeds are all implemented on XML technology. XPath could be used to integrate various combinations of any of these technologies. A good example of this type of integration was the weekend planner application I used to find the perfect Saturday activity.

The application reads an RSS feed of a local community events calendar. It leverages XPath to read the zip codes and dates of each event. These zip codes and dates are then sent to a Web service that provides the weather forecast for that area of town, on that day. That information showed me that a picnic at Blanchard Park on Saturday was a better idea than going to the carnival at the Central Florida Fair Grounds on Sunday.

XPath can be used anytime you need a subset of data from a larger XML dataset. Its use is analogous to the use of Regular Expressions. Regular Expressions retrieve a substring based on pattern matching within a string. They are very powerful, although one might not think so at first look. This is because ColdFusion implements Regular Expressions as a single argument used in a small handful of functions. A deeper look into Regular Expressions would reveal book after book dedicated to its intricacies. In the same manner, XPath makes its ColdFusion appearance as a lone argument of one function, yet has novels dedicated to its deeper functionality.

XPath is leveraged via the function XmlSearch(). XmlSearch() requires two parameters: xmlDoc; an XML Object, and XPathString; and XPath expression. It returns an array, with each element of the array containing an XML node. As stated before, XmlSearch() cannot return strings, Booleans, or numbers.

The first parameter of XmlSearch() is an XML Object. When XML is read in by ColdFusion it is treated just like any other string, however calling the function XmlParse() on that string will load it into memory, create, and return a ColdFusion XML Object. Figure 1 shows the comparison of an unparsed XML document dumped on the left, and the same XML document parsed and dumped on the right.

Now that our XML has been converted to an object, we can run our first XPath expression against it. In order to understand how to write XPath expressions, we must understand and identify the different parts and elements that make up an XML document.

The easiest way to identify the parts of an XML document is to compare it to a file structure. If we were to run the command "C:\inetpub\wwwroot" in Windows, the OS would open the "wwwroot" directory, showing all of its contents. In this example, "C:" of course is a reference to the disk, and "inetpub\wwwroot" tells the system to look into the "wwwroot" folder, which is nested inside the "inetpub" folder. As nomenclature of nested sets goes, it could be said that "inetpub" is the parent "wwwroot." Likewise, "wwwroot" is the child of "inetpub." Extending that paradigm out, "C:" would then be a grand parent of "wwwroot." In such instances, "C:" would be known as an ancestor and "wwwroot" would be known as a descendant. Since "C:" is the absolute oldest ancestor or the top node in the nested set, it is also given a special name - root.

If we were to change our command to "C:/inetpub" and run it, the "inetpub" folder would open showing all of its children. Besides "wwwroot," there might be other directories or files. For example, I have an "ftproot" folder nested below "inetpub." Since "inetpub" is a parent to "ftproot" as well as to "wwwroot," "ftproot" and "wwwroot" are said to be siblings.

XML nodes can also be identified using the same rules as the "family-name-game" above. Listing 1 is a breakdown of every battle from Iron Chef America: The Series (Season 1). In it, the "ICA" node is equivalent to "C:." It is the root node (also known as the document node in XML), an ancestor to the "IronChef" node, and parent to the "Battle" node. Since the "IronChef" and "Battle" nodes share the parent node "Battle," they are siblings. In XPath, just as in our file path example above, we can reference the "IronChef" node using a simple path syntax: "/ICA/Battle/IronChef."

More Stories By Nik Molnar

Nik Molnar is a ColdFusion/Flex developer with over seven years experience. He has led teams through the development of enterprise applications for the mortgage, sports ticketing, and stock industries. He is an amateur Iron Chef and posts regularly at his blog: foodDuo.com. He lives with his wife Katy and his dog Jacques in Orlando, Florida.

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.


IoT & Smart Cities Stories
The deluge of IoT sensor data collected from connected devices and the powerful AI required to make that data actionable are giving rise to a hybrid ecosystem in which cloud, on-prem and edge processes become interweaved. Attendees will learn how emerging composable infrastructure solutions deliver the adaptive architecture needed to manage this new data reality. Machine learning algorithms can better anticipate data storms and automate resources to support surges, including fully scalable GPU-c...
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 great conferences, helping you discover new conferences and increase your return on investment.
Poor data quality and analytics drive down business value. In fact, Gartner estimated that the average financial impact of poor data quality on organizations is $9.7 million per year. But bad data is much more than a cost center. By eroding trust in information, analytics and the business decisions based on these, it is a serious impediment to digital transformation.
SYS-CON Events announced today that Silicon India 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. Published in Silicon Valley, Silicon India magazine is the premiere platform for CIOs to discuss their innovative enterprise solutions and allows IT vendors to learn about new solutions that can help grow their business.
We are seeing a major migration of enterprises applications to the cloud. As cloud and business use of real time applications accelerate, legacy networks are no longer able to architecturally support cloud adoption and deliver the performance and security required by highly distributed enterprises. These outdated solutions have become more costly and complicated to implement, install, manage, and maintain.SD-WAN offers unlimited capabilities for accessing the benefits of the cloud and Internet. ...
Founded in 2000, Chetu Inc. is a global provider of customized software development solutions and IT staff augmentation services for software technology providers. By providing clients with unparalleled niche technology expertise and industry experience, Chetu has become the premiere long-term, back-end software development partner for start-ups, SMBs, and Fortune 500 companies. Chetu is headquartered in Plantation, Florida, with thirteen offices throughout the U.S. and abroad.
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...
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
DXWorldEXPO LLC announced today that "IoT Now" was named media sponsor of CloudEXPO | DXWorldEXPO 2018 New York, which will take place on November 11-13, 2018 in New York City, NY. IoT Now explores the evolving opportunities and challenges facing CSPs, and it passes on some lessons learned from those who have taken the first steps in next-gen IoT services.
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...