XSLT recursive sort by attribute

I found multiple questions and answers regarding nested/recursive sort using XSLT, but was not able to map it on my situation.

My situation:

• "set" element can consist of 0 or more "property" elements
• a "set" element can consist of 0 or more subsets
• both set and property elements consist of attribute "key"
• I want to sort the "set"s by "key" attribute, and per "set": sort by "k开发者_JAVA技巧ey" of "properties" elements

The XML looks something like:

<set key="...">
  <property key="..."/>
  <property key="..."/>
  <property key="..."/>
  <set key="...">
    <set key="...>
      <property key="..."/>
      <property key="..."/>
      <property key="..."/>
    </set>
  </set>
</set>

Suggestions?

In simple situations it can be achieved like this:

<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes"/>
    <xsl:template match="@* | node()">
        <xsl:copy>
            <xsl:apply-templates select="@* | node()">
                <xsl:sort select="@key" data-type="number"/>
            </xsl:apply-templates>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

Applied to this XML:

<set key="1">
  <property key="6"/>
  <property key="8"/>
  <property key="1"/>
  <set key="3">
    <set key="0">
      <property key="4"/>
      <property key="2"/>
      <property key="9"/>
    </set>
  </set>
</set>

Result will be:

<set key="1">
    <property key="1"></property>
    <set key="3">
        <set key="0">
            <property key="2"></property>
            <property key="4"></property>
            <property key="9"></property>
        </set>
    </set>
    <property key="6"></property>
    <property key="8"></property>
</set>

I guess real-life app is more complex, but your example doesn't show that.

Personally, I don't think XSL-T is suited for this sort of thing. It's an XML transformation language, not a programming language for sorting.

I think it'd be better to use the right tool for the job: Use a language like Java or C# to produce the XML in sorted form, then use XSL-T to transform it.

If you're struggling with it, you probably should re-think the approach.