XML Tutorial/XSLT stylesheet/Introduction

Batch-Processing Nodes

The xsl:for-each element processes all the nodes in the same way, one after the other. 
 
File: Data.xml
 
<?xml version="1.0"?>
<employees>
  <animal>
    <name language="English">T1</name>
    <name language="Latin">T2</name>
    <projects>
      <project>project1</project>
    </projects>
  </animal>
</employees>
File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  version="1.0">
  <xsl:template match="animal">
    <paragraph align="center">
      <br />
      <font size="+3">
        <xsl:apply-templates select="name" />
      </font>
    </paragraph>
    <table width="100%" border="2">
      <tr>
        <td>Subspecies</td>
        <td>Region</td>
        <td>Number</td>
        <td>As Of</td>
      </tr>
      <xsl:for-each select="subspecies">
        <tr>
          <td>
            <xsl:apply-templates select="name" />
          </td>
          <td>
            <xsl:value-of select="region" />
          </td>
          <td>
            <xsl:value-of select="population" />
          </td>
          <td>
            <xsl:value-of select="population/@year" />
          </td>
        </tr>
      </xsl:for-each>
    </table>
  </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?>
  <paragraph align="center"><br/><font size="+3">T1T2</font></paragraph><table width="100%" border="2"><tr><td>Subspecies</th><td>Region</th><td>Number</th><td>As Of</th></tr></table>

Every XSL stylesheet must start with xsl:stylesheet element

The attribute version="1.0" specifies version of XSL(T) specification. 
File: Data.xml

<em>Hello, world</em>
File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

</xsl:stylesheet>

Insert html tags into template

File: Data.xml

<employee>
  <firstName>Joe</firstName>
  <surname>Smith</surname>
</employee>
File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="employee">
      <b>
        <xsl:apply-templates select="firstName"/>
      </b>
      <b>
        <xsl:apply-templates select="surname"/>
      </b>
    </xsl:template>
    <xsl:template match="surname">
      <i>
        <xsl:value-of select="."/>
      </i>
    </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?><b>Joe</b><b><i>Smith</i></b>

With XSL you can modify any source text and produce different output from the same source file

"//title" matches any title element anywhere in the document.
"//author" matches any author element anywhere in the document.
"/" matches the root element.

File: Data.xml
<data>
    <title>XSL</title>
    <author>John Smith</author>
</data>
File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
      <h1>
        <xsl:value-of select="//title"/>
      </h1>
      <h2>
        <xsl:value-of select="//author"/>
      </h2>
    </xsl:template>
    <xsl:template match="/">
      <h2>
        <xsl:value-of select="//author"/>
      </h2>
      <h1>
        <xsl:value-of select="//title"/>
      </h1>
    </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?><h2>John Smith</h2><h1>XSL</h1>

"xsl:template xsl:value-of"

An XSL processors parses an XML source and tries to find a matching template rule. 
If it does, instructions inside matching template are evaluated.
File: Data.xml
<data>
    <bold>Hello, world.</bold>
    <red>I am </red>
    <italic>fine.</italic>
</data>
File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="bold">
      <paragraph>
        <b>
          <xsl:value-of select="."/>
        </b>
      </paragraph>
    </xsl:template>
    <xsl:template match="red">
      <paragraph style="color:red">
        <xsl:value-of select="."/>
      </paragraph>
    </xsl:template>
    <xsl:template match="italic">
      <paragraph>
        <i>
          <xsl:value-of select="."/>
        </i>
      </paragraph>
    </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?>
    <paragraph><b>Hello, world.</b></paragraph>
    <paragraph style="color:red">I am </paragraph>
    <paragraph><i>fine.</i></paragraph>

"xsl:value-of xsl:apply-templates"

File: Data.xml
<employee>
  <firstName>Joe</firstName>
  <surname>Smith</surname>
</employee>

File: Transform.xslt
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="employee">
      <b>
        <xsl:value-of select="."/>
      </b>
    </xsl:template>
    <xsl:template match="surname">
      <i>
        <xsl:value-of select="."/>
      </i>
    </xsl:template>
</xsl:stylesheet>
Output:
<?xml version="1.0" encoding="UTF-8"?><b>
  Joe
  Smith
</b>