Explanation: Using Microsoft.XMLDOM to work with data feeds in VBScript
Posted by: Jerry Lees
Development, Microsoft.XMLDOM, XML, 360voice, VBScript, DataManagement
You may recall we recently worked with a cool little script that itself didn’t have anything to do with systems administration, the 360voice API script in a previous post, but the concepts can be used in many different areas since XML data feeds are ever becoming the standard way to communicate related data between applications and systems.
In this script, I used many topics we’ve previously discussed and added a powerful object, Microsoft.XMLDOM. Essentially, DOM stands for Document Object Model– which is a way for the document to describe and relate the data it contains. Here is an example XML document header for “mydata”
<?xml version=”1.0″?>
<!DOCTYPE Mydata SYSTEM “mydata.dtd”>
This essentially in the first line tells us the file is an XML document, Version 1.0 to be specific, and in the second line tells us the Document Type Definition file that we can have the parser verify the XML file against. DTD’s and XML Schemas are beyond the scope of what we’re discussing but can be very useful becasue they define the rules by which a XML document must conform to be considered valid– however they are not required to be in an XML file.
After these lines the XML file has nodes and child nodes in it. This is where the bulk of our work was done going through the nodes and pulling out child nodes and values. In this illustration we’ll use the following URL to my XML Game data at 360voice.com (note the data will change over time, but the datastructure should stay pretty much the same)
As of this moment, the file looks like:
<?xml version=”1.0″ encoding=”ISO-8859-1″ ?>
<api>
<info>
<version>1.2</version>
<gamertag>jlees</gamertag>
</info>
<gamerscore>
<score>
<value>23740</value>
<date>3/20/2008 4:42:02 AM</date>
</score>
<score>
<value>23740</value>
<date>3/19/2008 4:45:18 AM</date>
</score>
</gamerscore>
</api>
Notice how the main Node (The “document” Node) is titled api? The XML Parser automatically read that entire node in at the load of the document. After that we have nodes called info and gamerscore that both contain data and/or child nodes.
the info tag contains the version and gamertag values, you’ll notice I used the gamertag value in the script to pull the name of the gamertag with this line of the script code after checking to see if the currently looped through tag had the name “info”:
WScript.Echo GetTagValue(x,”gamertag”)
See how that works? This example was pretty simple since it was just off the root. The score value and date were a bit harder to get at, but not to bad.
They are contained in a child node called “score”, but they are a child of gamerscore– so you’ll see that I check to see if the tag is “gamerscore” and then loop through the score tag separately looking for each instance of the node called score and pulling the tag value and placing it into an array called gamerscore.
All pretty straightforward. There are certainly better ways to deal with XML than writing code tightly around the XML itself, but this illustrates the use of Microsoft.XMLDOM and explains the heirarchial nature of XML nicely the way it’s been coded.
See if you can play around with the code and make it better! Thanks again to the folks at 360voice for providing the API and it’s documentation!
Happy coding and have fun!
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