XSl Templates

XSL processors do parses the XML source and tries to find out the matching template rule. If it do find it, then the instructions inside the matching template is evaluated.

XML source

<?xml version="1.0"?>
<xslTutorial >

<bold>Hello, world.</bold>
<red>I am </red>
<italic>fine.</italic>
</xslTutorial>

HTML output 1
<P>
<B>Hello, world.</B></P>
<P style="color:red">I am </P>
<P>
<i>fine.</i></P>

XSL stylesheet 1

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="bold">
<P><B><xsl:value-of select="."/></B></P>
</xsl:template>
<xsl:template match="red">
<P style="color:red"><xsl:value-of select="."/></P>
</xsl:template>
<xsl:template match="italic">
<P><i><xsl:value-of select="."/></i></P>
</xsl:template>
</xsl:stylesheet>

Location Paths

Parts of the XML document to which the template should be applied are been determined by the Location Paths. A required syntax is specified in XPath specification. Simple cases do look similar to the filesystem addressing. see Stylesheet 1

XML source

<?xml version="1.0"?>
<xslTutorial >
<AAA id='a1' pos='start'>
<BBB id='b1'/>
<BBB id='b2'/>
</AAA>
<AAA id='a2'>
<BBB id='b3'/>
<BBB id='b4'/>
<CCC id='c1'>
<DDD id='d1'/>
</CCC>
<BBB id='b5'>
<CCC id='c2'/>
</BBB>
</AAA>
</xslTutorial>

HTML output 1

<DIV style="color:purple">BBB id=b1</DIV>
<DIV style="color:purple">BBB id=b2</DIV>
<DIV style="color:purple">BBB id=b3</DIV>
<DIV style="color:purple">BBB id=b4</DIV>
<DIV style="color:red">DDD id=d1</DIV>
<DIV style="color:purple">BBB id=b5</DIV>

XSL stylesheet 1

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="BBB">
<DIV style="color:purple">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
<xsl:template match="/xslTutorial/AAA/CCC/DDD">
<DIV style="color:red">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
</xsl:stylesheet>

The Processing always do starts with the template match="/" . This is a root element and its only child is the document element, in our case it is XSl Tutorial. Many of the stylesheets do not contains this element explicitly. When the explicit template does not exist implicit the template, which do contains the instruction is called. This means: It processes all the childrens of the current node, including the text nodes.

Wildcard

A Template can do match from the selection of a location paths, individual paths being separated with the "|". (see Stylesheet 1). The wildcard * selects all the possibilities. Compare the Stylesheet 1 with the Stylesheet 2.

XML source

<?xml version="1.0"?>
<xslTutorial >
<employee>
<firstName>Joe</firstName>
<surname>Smith</surname>
</employee>
</xslTutorial>

HTML output 1

<DIV>[template: firstName outputs Joe ]</DIV>
<DIV>[template: surname outputs Smith ]</DIV>

XSL stylesheet 1

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="firstName|surname">
<DIV><xsl:text> [template: </xsl:text>
<xsl:value-of select="name()"/>
<xsl:text> outputs </xsl:text>
<xsl:apply-templates/ >
<xsl:text> ]</xsl:text> </DIV>
</xsl:template>
</xsl:stylesheet>

XSL stylesheet 2

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="*">
<DIV><xsl:text> [template: </xsl:text>
<xsl:value-of select="name()"/>
<xsl:text> outputs </xsl:text>
<xsl:apply-templates/ >
<xsl:text> ]</xsl:text> </DIV>
</xsl:template>
</xsl:stylesheet>

XSL Modes

Modes in XSL do allow the element to be processed for multiple times, each time producing different result. In the Stylesheet 2 one of the modes do not exist.

XML source

<?xml version="1.0"?>
<xslTutorial >
<AAA id='a1' pos='start'>
<BBB id='b1'/>
<BBB id='b2'/>
</AAA>
<AAA id='a2'>
<BBB id='b3'/>
<BBB id='b4'/>
<CCC id='c1'>
<CCC id='c2'/>
</CCC>
<BBB id='b5'>
<CCC id='c3'/>
</BBB>
</AAA>
</xslTutorial>

HTML output 1

<DIV style="color:red">CCC id=c1</DIV>
<DIV style="color:red">CCC id=c2</DIV>
<DIV style="color:red">CCC id=c3</DIV>
<DIV style="color:blue">CCC id=c1</DIV>
<DIV style="color:blue">CCC id=c2</DIV>
<DIV style="color:blue">CCC id=c3</DIV>
<DIV style="color:purple">CCC id=c1</DIV>
<DIV style="color:purple">CCC id=c2</DIV>
<DIV style="color:purple">CCC id=c3</DIV>

XSL stylesheet 1

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="/">
<xsl:apply-templates select="//CCC" mode="red"/>
<xsl:apply-templates select="//CCC" mode="blue"/>
<xsl:apply-templates select="//CCC"/>
</xsl:template>
<xsl:template match="CCC" mode="red">
<DIV style="color:red">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
<xsl:template match="CCC" mode="blue">
<DIV style="color:blue">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
<xsl:template match="CCC">
<DIV style="color:purple">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
</xsl:stylesheet>

XSL stylesheet 2

<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:template match="/">
<xsl:apply-templates select="//CCC" mode="red"/>
<xsl:apply-templates select="//CCC" mode="yellow"/>
</xsl:template>
<xsl:template match="CCC" mode="red">
<DIV style="color:red">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
<xsl:template match="CCC">
<DIV style="color:purple">
<xsl:value-of select="name()"/>
<xsl:text> id=</xsl:text>
<xsl:value-of select="@id"/>
</DIV>
</xsl:template>
</xsl:stylesheet>

The Template Priority

Very often several of the templates do match the selected element in the XML source. It should be therefore decided which one to use. Templates are been ordered according to their priority which can be specified with the priority attributte. If a template do not contain this attribute, its priority is been calculated according to several rules.

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