XSLT <template>
Define transformation rules with templates
📋 What is xsl:template?
The xsl:template element defines reusable transformation rules in XSLT. Templates match specific XML patterns and specify how to transform matched nodes into the desired output format using the match attribute.
<!-- Basic Template -->
<xsl:template match="book">
<div>
<h2><xsl:value-of select="title"/></h2>
</div>
</xsl:template>
Template Features
Match Pattern
Select nodes to transform
<xsl:template match="/">Named Templates
Reusable template functions
<xsl:template name="header">Priority
Control template precedence
<xsl:template priority="2">Mode
Apply templates conditionally
<xsl:template mode="summary">🔹 Basic Template Structure
Templates use the match attribute to specify which XML nodes they transform. The template body contains the output structure and XSLT instructions for processing the matched nodes.
<!-- Input XML -->
<library>
<book>
<title>XML Guide</title>
<author>John Doe</author>
</book>
</library>
<!-- XSLT with Templates -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<!-- Root template -->
<xsl:template match="/">
<html>
<body>
<xsl:apply-templates/>
</body>
</html>
</xsl:template>
<!-- Book template -->
<xsl:template match="book">
<div class="book">
<h2><xsl:value-of select="title"/></h2>
<p>By: <xsl:value-of select="author"/></p>
</div>
</xsl:template>
</xsl:stylesheet>Output:
XML Guide
By: John Doe
🔹 Named Templates
Named templates work like functions that you can call from anywhere in your stylesheet. Use xsl:call-template to invoke them, making your code more modular and reusable.
<!-- Define named template -->
<xsl:template name="formatPrice">
<xsl:param name="amount"/>
<span class="price">$<xsl:value-of select="$amount"/></span>
</xsl:template>
<!-- Use named template -->
<xsl:template match="product">
<div>
<h3><xsl:value-of select="name"/></h3>
<xsl:call-template name="formatPrice">
<xsl:with-param name="amount" select="price"/>
</xsl:call-template>
</div>
</xsl:template>
<!-- Input XML -->
<product>
<name>Laptop</name>
<price>999.99</price>
</product>Output:
Laptop
$999.99🔹 Template Matching Patterns
Templates can match different node types and patterns using XPath expressions. This allows precise control over which elements get transformed and how.
<!-- Match root -->
<xsl:template match="/">
<html><body><xsl:apply-templates/></body></html>
</xsl:template>
<!-- Match specific element -->
<xsl:template match="title">
<h1><xsl:value-of select="."/></h1>
</xsl:template>
<!-- Match with attribute -->
<xsl:template match="book[@category='fiction']">
<div class="fiction-book">
<xsl:apply-templates/>
</div>
</xsl:template>
<!-- Match any element -->
<xsl:template match="*">
<p><xsl:value-of select="."/></p>
</xsl:template>
<!-- Match text nodes -->
<xsl:template match="text()">
<xsl:value-of select="."/>
</xsl:template>Pattern Types:
/ - Document root
element - Specific element
element[@attr] - With attribute
* - Any element
🔹 Template Priority
When multiple templates match the same node, XSLT uses priority to determine which template to apply. You can set explicit priority values or rely on default precedence rules.
<!-- Low priority (default = 0) -->
<xsl:template match="item">
<p>Generic item</p>
</xsl:template>
<!-- High priority -->
<xsl:template match="item[@special='true']" priority="2">
<p class="special">Special item!</p>
</xsl:template>
<!-- Input XML -->
<items>
<item>Regular</item>
<item special="true">Premium</item>
</items>Output:
Generic item
Special item!
🔹 Template Modes
Modes allow you to process the same nodes differently in different contexts. This is useful when you need multiple representations of the same data in your output.
<!-- Normal mode -->
<xsl:template match="book">
<div class="book-full">
<h2><xsl:value-of select="title"/></h2>
<p><xsl:value-of select="description"/></p>
<p>Price: $<xsl:value-of select="price"/></p>
</div>
</xsl:template>
<!-- Summary mode -->
<xsl:template match="book" mode="summary">
<li><xsl:value-of select="title"/> - $<xsl:value-of select="price"/></li>
</xsl:template>
<!-- Usage -->
<xsl:template match="/">
<h1>Quick List</h1>
<ul>
<xsl:apply-templates select="//book" mode="summary"/>
</ul>
<h1>Full Details</h1>
<xsl:apply-templates select="//book"/>
</xsl:template>Output:
Quick List
- XML Guide - $29.99
Full Details
XML Guide
Complete guide to XML
Price: $29.99
🔹 Complete Template Example
This comprehensive example demonstrates multiple templates working together to transform a complex XML structure into a formatted HTML page with different sections.
<!-- Input XML -->
<store>
<category name="Electronics">
<product featured="true">
<name>Laptop</name>
<price>999</price>
</product>
<product>
<name>Mouse</name>
<price>25</price>
</product>
</category>
</store>
<!-- XSLT -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<html>
<body>
<h1>Product Catalog</h1>
<xsl:apply-templates/>
</body>
</html>
</xsl:template>
<xsl:template match="category">
<div class="category">
<h2><xsl:value-of select="@name"/></h2>
<xsl:apply-templates select="product"/>
</div>
</xsl:template>
<xsl:template match="product">
<div class="product">
<h3><xsl:value-of select="name"/></h3>
<p>$<xsl:value-of select="price"/></p>
</div>
</xsl:template>
<xsl:template match="product[@featured='true']" priority="1">
<div class="product featured">
<h3>⭐ <xsl:value-of select="name"/></h3>
<p>$<xsl:value-of select="price"/></p>
</div>
</xsl:template>
</xsl:stylesheet>HTML Output:
Product Catalog
Electronics
⭐ Laptop
$999
Mouse
$25