Little Black Book - XML

With a sound foundation in XML theory behind you, it's now time to address the other half of the jigsaw - actually converting all that marked-up data into something useful. This first article in a two-part series examines the need, rationale and basic concepts of XSLT, the Extensible Stylesheet Language for Transformations, with sample code and examples.

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By: icarus, (c) Melonfire

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August 15, 2001

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One more example, this one demonstrating how powerful this ability to recursively apply templates is. Consider the following example:

<?xml version="1.0"?>
<?xml:stylesheet type="text/xsl" href="address.xsl"?>
<addressbook>
<record>
<name>John 
Smith</name>
<street>24, Main Street</street>
<city>Poodle Springs</city>
<zip>16628</zip>
<country>USA</country>
</record>
<record>
<name>Sherlock 
Holmes</name>
<street>122B, Baker Street</street>
<city>London</city>
<zip>12367</zip>
<country>United 
Kingdom</country>
</record>
<record>
<name>Jane Doe</name>
<street>64 
Fedwikstrasse</street>
<city>Antwerp</city>
<zip>848222</zip>
<country>Brussels</country>
</record>
</addressbook>

Now, since this data follows a very simple structure, and moreover I'm not very concerned about the order in which the various records appear, I can format it and present it as HTML with just two XSLT template rules:


<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template 
match="/addressbook">
<html>
<head>
<basefont face="Arial" size="2"/>
</head>
<body>
<h1>My 
Address Book</h1>
<xsl:apply-templates />
</body>
</html>
</xsl:template>
<xsl:template 
match="record">
<b><xsl:value-of select="name" /></b>
<br />
<xsl:value-of 
select="street" />
<br />
<xsl:value-of select="city" /> - <xsl:value-of 
select="zip" />
<br />
<xsl:value-of select="country" />
<p />
</xsl:template>
</xsl:stylesheet>

The first rule locates the document element and places the standard HTML headers and footers in the corresponding positions in the result tree. Next, the

<xsl:apply-templates />

instruction processes all the children of this node - in this case, these are all "record" elements, for which there is a corresponding template rule. Each time a record is located via the "record" element, the template rule is invoked and a new fragment added to the result tree. At the end of the process, a composite tree is built out of all the different chunks - and it looks like this:


<html>
<head>
<basefont face="Arial" size="2">
</head>
<body>
<h1>My 
Address Book</h1>
<b>John Smith</b><br>24, Main Street<br>Poodle 
Springs - 16628<br>USA<p></p>
<b>Sherlock Holmes</b><br>122B, 
Baker Street<br>London - 12367<br>United
Kingdom<p></p>
<b>Jane 
Doe</b><br>64 Fedwikstrasse<br>Antwerp - 848222<br>Brussels<p></p>
</body>
</html>

And that just about covers the essential concepts behind XSL transformations. In the second part of this article, I will be looking at a few of XSLT's more advanced constructs, demonstrating how to add loops and conditional tests to your XSLT templates.

Note: All examples in this article have been tested on Microsoft Internet Explorer 5.5 and Saxon 6.4.3. Examples are illustrative only, and are not meant for a production environment. YMMV!