XSLT templates and recursion

Question

Im new to XSLT and am having some problems trying to format an XML document which has recursive nodes.

My XML Code:

Hopefully my XML shows:

• All <item> are nested with <items>
• An item can have either just attributes, or sub nodes
• The level to which <item> nodes are nested can be infinently deep

<?xml version="1.0" encoding="utf-8" ?> 
- <items>
  <item groupID="1" name="Home" url="//" /> 
- <item groupID="2" name="Guides" url="/Guides/">
- <items>
- <item groupID="26" name="Online-Poker-Guide" url="/Guides/Online-Poker-Guide/">
- <items>
- <item>
  <id>107</id> 
- <title>
- <![CDATA[ Poker Betting - Online Poker Betting Structures
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-betting-structures
  ]]> 
  </url>
  </item>
- <item>
  <id>114</id> 
- <title>
- <![CDATA[ Beginners&#39; Poker - Poker Hand Ranking
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-hand-ranking
  ]]> 
  </url>
  </item>
- <item>
  <id>115</id> 
- <title>
- <![CDATA[ Poker Terms - 4th Street and 5th Street
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-poker-terms
  ]]> 
  </url>
  </item>
- <item>
  <id>116</id> 
- <title>
- <![CDATA[ Popular Poker - The Popularity of Texas Hold&#39;em
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-popularity-texas-holdem
  ]]> 
  </url>
  </item>
- <item>
  <id>364</id> 
- <title>
- <![CDATA[ The Impact of Traditional Poker on Online Poker (and vice versa)
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-tradional-vs-online
  ]]> 
  </url>
  </item>
- <item>
  <id>365</id> 
- <title>
- <![CDATA[ The Ultimate, Absolute Online Poker Scandal
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/online-poker-scandal
  ]]> 
  </url>
  </item>
  </items>
- <items>
- <item groupID="27" name="Beginners-Poker" url="/Guides/Online-Poker-Guide/Beginners-Poker/">
- <items>
+ <item>
  <id>101</id> 
- <title>
- <![CDATA[ Poker Betting - All-in On the Flop
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/poker-betting-all-in-on-the-flop
  ]]> 
  </url>
  </item>
+ <item>
  <id>102</id> 
- <title>
- <![CDATA[ Beginners&#39; Poker - Choosing an Online Poker Room
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/beginners-poker-choosing-a-room
  ]]> 
  </url>
  </item>
+ <item>
  <id>105</id> 
- <title>
- <![CDATA[ Beginners&#39; Poker - Choosing What Type of Poker to Play
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/beginners-poker-choosing-type-to-play
  ]]> 
  </url>
  </item>
+ <item>
  <id>106</id> 
- <title>
- <![CDATA[ Online Poker - Different Types of Online Poker
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/online-poker
  ]]> 
  </url>
  </item>
+ <item>
  <id>109</id> 
- <title>
- <![CDATA[ Online Poker - Opening an Account at an Online Poker Site
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/online-poker-opening-an-account
  ]]> 
  </url>
  </item>
+ <item>
  <id>111</id> 
- <title>
- <![CDATA[ Beginners&#39; Poker - Poker Glossary
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/beginners-poker-glossary
  ]]> 
  </url>
  </item>
+ <item>
  <id>117</id> 
- <title>
- <![CDATA[ Poker Betting - What is a Blind?
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/poker-betting-what-is-a-blind
  ]]> 
  </url>
  </item>
- <item>
  <id>118</id> 
- <title>
- <![CDATA[ Poker Betting - What is an Ante?
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/poker-betting-what-is-an-ante
  ]]> 
  </url>
  </item>
+ <item>
  <id>119</id> 
- <title>
- <![CDATA[ Beginners Poker - What is Bluffing?
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/online-poker-what-is-bluffing
  ]]> 
  </url>
  </item>
- <item>
  <id>120</id> 
- <title>
- <![CDATA[ Poker Games - What is Community Card Poker?
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/online-poker-what-is-community-card-poker
  ]]> 
  </url>
  </item>
- <item>
  <id>121</id> 
- <title>
- <![CDATA[ Online Poker - What is Online Poker?
  ]]> 
  </title>
- <url>
- <![CDATA[ /Guides/Online-Poker-Guide/Beginners-Poker/online-poker-what-is-online-poker
  ]]> 
  </url>
  </item>
  </items>
  </item>
  </items>
  </item>
  </items>
  </item>
  </items>

The XSL code:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" indent="yes"/>

    <xsl:template name="loop">
        <xsl:for-each select="items/item">
            <ul>
            <li><xsl:value-of select="@name" /></li>
            <xsl:if test="@name and child::node()">
                <ul>
                    <xsl:for-each select="items/item">
                        <li><xsl:value-of select="@name" />test</li>
                    </xsl:for-each>
                </ul>
                <xsl:call-template name="loop" />
            </xsl:if>
            <xsl:if test="child::node() and not(@name)">
                <xsl:for-each select="/items">
                    <li><xsl:value-of select="id" /></li>
                </xsl:for-each>
            </xsl:if>
            </ul>
        </xsl:for-each>
        <xsl:for-each select="item/items/item">
            <li>hi</li>
        </xsl:for-each>
    </xsl:template>

    <xsl:template match="/" name="test">
            <xsl:call-template name="loop" />
    </xsl:template>

</xsl:stylesheet>

Im trying to write the XSL so that every <items> node will render a <ul> and every <items> node will render an <li>.

The XSL needs to be recursive because i cant tell how deep the nested nodes will go.

Can anyone help?

Regards, Al

Answer 1

This is easy. The XSLT processor does all the recursion and the looping for you, all you need to do is to specify templates for nodes you want to handle.

<xsl:stylesheet 
  version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>
  <!-- <items> with <item> children becomes <ul> -->
  <xsl:template match="items[item]">
    <ul>
      <xsl:apply-templates select="item" />
    </ul>
  </xsl:template>

  <!-- <items> without <item> children is not handled -->
  <xsl:template match="items[not(item)]" />

  <!-- <item> with @name becomes <li> -->
  <xsl:template match="item[@name]">
    <li>
      <xsl:value-of select ="@name" />
      <xsl:apply-templates select="items" />
    </li>
  </xsl:template>

  <!-- <item> without @name becomes <li>, too -->
  <xsl:template match="item[not(@name)]">
    <li>
      <xsl:value-of select ="id" />
      <xsl:apply-templates select="items" />
    </li>
  </xsl:template>
</xsl:stylesheet>

The <xsl:apply-templates> always is the recursive/iterative step in XSLT. It takes any nodes that fit its select expression and finds templates for them.

Your job is it to craft an appropriate select expression, supply a template for every node you want to handle and otherwise get out of the way. ;-) Resist the urge to cram everything into one big template or use <xsl:for-each> just because it feels convenient - it is not. Separate templates create more reusable and maintainable, less deeply nested code, and XSLT processors are optimized for template handling, so this might even be the more efficient approach.

Answer 2

You should be able to do this without writing a loop, if I understand your needs correctly.

It's generally better to use a more declarative style, in this instance writing a template matching the <items> tag and converting it to a <ul> and another matching <item> converting it to a <li>. An <xsl:apply-templates/> call inside both templates would supply the recursion.

Answer 3

The following stylesheet performs the specified formatting. Note the use of xsl:apply-templates to recurse down the XML tree. See 5.4 Applying Template Rules for more information.

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes"/>
    <xsl:template match="/">
        <xsl:apply-templates select="items"/>
    </xsl:template>

    <xsl:template match="items">
        <ul>
            <xsl:apply-templates select="item" />
        </ul>
    </xsl:template>

    <xsl:template match="item">
        <li>
            <xsl:choose>
                <xsl:when test="@name">
                    <xsl:value-of select="@name"/>
                </xsl:when>
                <xsl:otherwise>
                    <xsl:value-of select="id"/>
                </xsl:otherwise>
            </xsl:choose>
            <xsl:apply-templates select="items" />
        </li>
    </xsl:template>
</xsl:stylesheet>

Answer 4

I think you can just write the XSL-T to match on <item>. The only way recursion would matter would be if you wanted to retain parent/child relationships. Matching on <item> will be sufficient if your requirement is to map each one to a bullet in an unordered list