xsl:template

Description

xsl:template is the central building block of every XSLT stylesheet. It defines a reusable chunk of transformation logic that is either matched automatically by the XSLT processor when it encounters nodes of a certain type, or called explicitly by name from other templates.

A template with a match attribute is a template rule. The processor evaluates the match pattern against nodes in the source tree and fires the template when a node matches. Patterns follow XPath abbreviated syntax with restrictions: only the child and attribute axes, predicates, and node tests are allowed — not full XPath expressions.

A template with only a name attribute is a named template, similar to a function or subroutine. It is never fired automatically; it must be called with xsl:call-template. A template may have both match and name, making it both matchable and callable.

The mode attribute allows the same source node to be processed by different templates in different contexts — for example, once to build a table of contents and again to build the body text. Templates with mode can only be activated by xsl:apply-templates with the same mode value.

Attributes

Examples

Match-based template rule

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<library>
  <book><title>Clean Code</title><year>2008</year></book>
  <book><title>Refactoring</title><year>1999</year></book>
</library>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/library">
    <books>
      <xsl:apply-templates select="book"/>
    </books>
  </xsl:template>

  <xsl:template match="book">
    <item year="{year}">
      <xsl:value-of select="title"/>
    </item>
  </xsl:template>
</xsl:stylesheet>

Output:

<books>
  <item year="2008">Clean Code</item>
  <item year="1999">Refactoring</item>
</books>

Named template with parameters

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<data><value>7</value></data>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text"/>

  <xsl:template name="repeat">
    <xsl:param name="text"/>
    <xsl:param name="count"/>
    <xsl:if test="$count > 0">
      <xsl:value-of select="$text"/>
      <xsl:call-template name="repeat">
        <xsl:with-param name="text" select="$text"/>
        <xsl:with-param name="count" select="$count - 1"/>
      </xsl:call-template>
    </xsl:if>
  </xsl:template>

  <xsl:template match="/data">
    <xsl:call-template name="repeat">
      <xsl:with-param name="text">*</xsl:with-param>
      <xsl:with-param name="count" select="value"/>
    </xsl:call-template>
  </xsl:template>
</xsl:stylesheet>

Output:

*******

Notes

• When two template rules match the same node, the processor uses conflict resolution: higher priority wins. If priorities are equal, the template with the more specific pattern wins (attribute patterns beat element patterns beat wildcard patterns). If still ambiguous, the processor may signal an error or pick the last declared template.
• Default built-in templates exist for every node type. For element and root nodes they recursively apply templates; for text and attribute nodes they copy the string value; for comments and processing instructions they produce nothing.
• The mode attribute value #all (XSLT 2.0+) matches in any mode; in XSLT 1.0 mode names must be an ordinary QName.
• Named templates do not have a match pattern, so they have no context node unless one is established by the caller.

See also

• xsl:apply-templates
• xsl:call-template
• xsl:with-param
• xsl:param