XSLT Custom Sort

Question

Is it possible in XSLT to sort in alphabetical order, with 5 items as \"preferred\".

i.e. given

Answer 1

Have you seen xsl:sort element, you can create two or more sorting criteria by combining xsl:apply-templates and xsl:sort

Indeeed, here is a sample where some countries comes first, in a predefined order, then all the others. Note that these are elements, not attributes as above.

<xsl:sort select="not(CountryValue = 'Scotland')"/>
<xsl:sort select="not(CountryValue = 'India')"/>
<xsl:sort select="CountryValue"/>

Sample result:

Country

Scotland   
Scotland 
Scotland 
India 
Afghanistan 
Afghanistan 
Afghanistan 
Afghanistan 
Afghanistan 
Afghanistan 
Albania 
Albania 
Albania 
Algeria

Answer 2

In your XSLT, are you able to make use of extension functions?

If so, one method is to modify the existing list of nodes in-line, to create a new node set but with an extra 'sortname' attribute on each node. You can then iterate through this new node set, sorting using the new 'sortname' attribute:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:exsl="urn:schemas-microsoft-com:xslt">
    <xsl:output method="xml" />
    <xsl:template match="/teams">
        <xsl:variable name="extendedteams">
        <xsl:for-each select="team">
            <xsl:copy>
                <xsl:copy-of select="@*" />
                <xsl:attribute name="sortname">
                    <xsl:choose>
                        <xsl:when test="@name='England' or @name='Northern Ireland' or @name='Republic of Ireland' or @name='Scotland' or @name='Wales'">1</xsl:when>
                        <xsl:otherwise>2</xsl:otherwise>
                    </xsl:choose>
                    <xsl:value-of select="@name" />
                </xsl:attribute>
            </xsl:copy>
        </xsl:for-each>
        </xsl:variable>
        <xsl:copy>
        <xsl:for-each select="exsl:node-set($extendedteams)/team">
            <xsl:sort select="@sortname" />

            <xsl:copy>
                <xsl:copy-of select="@*[name() != 'sortname']" />
            </xsl:copy>
        </xsl:for-each>
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

In the example above, I prefix a '1' onto any national team, and a '2' on any domestic team, and then sort on this new attribute.

See information on Node Sets to see what XSLT processers support which extensions.

Answer 3

You could do this:

<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:my="http://tempuri.org"
  exclude-result-prefixes="my"
>

  <xsl:output method="xml" indent="yes" /> 

  <my:data>
    <my:nationalteams>
      <my:team id="121" /><!-- Republic of Ireland -->
      <my:team id="123" /><!-- England -->
      <my:team id="126" /><!-- Northern Ireland -->
      <my:team id="142" /><!-- Scotland -->
      <my:team id="295" /><!-- Wales -->
    </my:nationalteams>
  </my:data>

  <xsl:template match="teams">
    <xsl:copy>
      <xsl:variable name="national" select="
        document('')/*/my:data/my:nationalteams/my:team
      " />
      <!-- national teams preferred -->
      <xsl:apply-templates select="team[@id = $national/@id]">
        <xsl:sort select="@name" />
      </xsl:apply-templates>
      <!-- other teams after them -->
      <xsl:apply-templates select="team[not(@id = $national/@id)]">
        <xsl:sort select="@name" />
      </xsl:apply-templates>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="team">
    <xsl:copy-of select="." />
  </xsl:template>

</xsl:stylesheet>

The whole <my:data> could be moved to a secondary XML/config file, where you can also leave off the "my" namespace.

After that, one line would need a small change:

<xsl:variable name="national" select="
  document('config.xml')/data/nationalteams/team
" />

The output of the above is somewhat unsurprising :-)

<teams>
  <team id="123" name="England" />
  <team id="126" name="Northern Ireland" />
  <team id="121" name="Republic of Ireland" />
  <team id="142" name="Scotland" />
  <team id="295" name="Wales" />
  <team id="49" name="Arsenal" />
  <team id="299" name="Bolton" />
  <team id="84" name="Chelsea" />
  <team id="110" name="Liverpool" />
  <team id="42" name="Manchester City" />
  <team id="13" name="Manchester United" />
  <team id="298" name="Tottenham Hotspur" />
</teams>

Answer 4

Tim C has already given a nice answer, but maybe a simpler way will suffice in your case. You could simply specify two xsl:sort conditions: The first will sort by preferred/not-preferred items, the second one alphabetically by name:

<?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="/teams">
    <teams>
      <xsl:for-each select="team">
        <xsl:sort select="not(@name = 'England' or @name='Northern Ireland'
                           or @name='Republic of Ireland' 
                           or @name='Scotland' or @name='Wales')" 
                  data-type="number"/>
        <xsl:sort select="@name"/>
        <team>
          <xsl:value-of select="@name"/>
        </team>
      </xsl:for-each>
    </teams>
  </xsl:template>
</xsl:stylesheet>

Please note that you have to invert the first condition using not(). The reason is that the boolean result of your expression is converted to a number (0 is false, 1 is true) and hence the items evaluating to 'false' will be listed first.