XML to XML with XSLT Sorting

Question

I have a couple of huge XMLs and I need to sort only a some small portions of them. As output I should have the same XML but with sorted substructures. Here is an example:

<testStructure>
<parentStruct>
    <firstpPreChild>some value here</firstpPreChild>
    <secondPreChild>some other value</secondPreChild>
    <thirdPreChild>third value here</thirdPreChild>
    <fourtPreChild>fourth value here</fourtPreChild>
    <struct id="5">
        <num>5</num>
    </struct>
    <struct id="4">
        <num>4</num>
    </struct>
    <struct id="1">
        <num>1</num>
    </struct>
    <struct id="2">
        <num>2</num>
    </struct>
    <struct id="3">
        <num>3</num>
    </struct>
     <firstAdditionalChild>some value here</firstAdditionalChild>
    <secondAdditionalChild>some other value</secondAdditionalChild>
    <thirdAdditionalChild>third value here</thirdAdditionalChild>
    <fourtAdditionalChild>fourth value here</fourtAdditionalChild>-->
</parentStruct>
<otherStruct>
    <firstChild>some value here</firstChild>
    <secondChild>some other value</secondChild>
    <thirdChild>third value here</thirdChild>
    <fourtChild>fourth value here</fourtChild>
</otherStruct>

should be transformed to

<testStructure>
<parentStruct>
    <firstpPreChild>some value here</firstpPreChild>
    <secondPreChild>some other value</secondPreChild>
    <thirdPreChild>third value here</thirdPreChild>
    <fourtPreChild>fourth value here</fourtPreChild>
    <struct id="1">
        <num>1</num>
    </struct>
    <struct id="2">
        <num>2</num>
    </struct>
    <struct id="3">
        <num>3</num>
    </struct>
    <struct id="4">
        <num>4</num>
    </struct>
    <struct id="5">
        <num>5</num>
    </struct>
     <firstAdditionalChild>some value here</firstAdditionalChild>
    <secondAdditionalChild>some other value</secondAdditionalChild>
    <thirdAdditionalChild>third value here</thirdAdditionalChild>
    <fourtAdditionalChild>fourth value here</fourtAdditionalChild>-->
</parentStruct>
<otherStruct>
    <firstChild>some value here</firstChild>
    <secondChild>some other value</secondChild>
    <thirdChild>third value here</thirdChild>
    <fourtChild>fourth value here</fourtChild>
</otherStruct>

as sort criteria can be used either num or @id. I've tried some variation like this:

<xsl:template match="node()|@*">
<xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
</xsl:copy>
</xsl:template>

which works, but shifts the sorted structure from its original position. Unfortunately I need the same structure as output.

Thanks in advance for the help!

What do you expect if the <struct> elements are not adjacent, but have some other child in between? — Christopher Creutzig
– Christopher Creutzig, Commented Feb 14, 2011 at 13:05

score 3 · Accepted Answer · 2011-02-15 21:23:38Z

3

Grouping by adjacent and then sorting, this XSLT 1.0 stylesheet:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:key name="kStructByFirstPreceding"
             match="struct"
             use="generate-id(
                     preceding-sibling::struct[
                        not(preceding-sibling::*[1]/self::struct)
                     ][1]
                  )"/>
    <xsl:template match="node()|@*" name="identity">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="struct[not(preceding-sibling::*[1]/self::struct)]">
        <xsl:apply-templates select=".|key('kStructByFirstPreceding',
                                           generate-id())"
                             mode="copy">
            <xsl:sort select="@id"/>
        </xsl:apply-templates>
    </xsl:template>
    <xsl:template match="struct"/>
    <xsl:template match="node()" mode="copy">
        <xsl:call-template name="identity"/>
    </xsl:template>
</xsl:stylesheet>

Output:

<testStructure>
    <parentStruct>
        <firstpPreChild>some value here</firstpPreChild>
        <secondPreChild>some other value</secondPreChild>
        <thirdPreChild>third value here</thirdPreChild>
        <fourtPreChild>fourth value here</fourtPreChild>
        <struct id="1">
            <num>1</num>
        </struct>
        <struct id="2">
            <num>2</num>
        </struct>
        <struct id="3">
            <num>3</num>
        </struct>
        <struct id="4">
            <num>4</num>
        </struct>
        <struct id="5">
            <num>5</num>
        </struct>
        <firstAdditionalChild>some value here</firstAdditionalChild>
        <secondAdditionalChild>some other value</secondAdditionalChild>
        <thirdAdditionalChild>third value here</thirdAdditionalChild>
        <fourtAdditionalChild>fourth value here</fourtAdditionalChild>--&gt; 
    </parentStruct>
    <otherStruct>
        <firstChild>some value here</firstChild>
        <secondChild>some other value</secondChild>
        <thirdChild>third value here</thirdChild>
        <fourtChild>fourth value here</fourtChild>
    </otherStruct>
</testStructure>

Simpler XSLT 2.0 solution:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="*[struct]">
        <xsl:copy>
            <xsl:for-each-group select="*"
                                group-adjacent="boolean(self::struct)">
                <xsl:apply-templates select="current-group()">
                    <xsl:sort select="@id[current-grouping-key()]"/>
                </xsl:apply-templates>
            </xsl:for-each-group>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

edited Feb 15, 2011 at 21:23

answered Feb 14, 2011 at 13:11

user357812

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5 Comments

Martin Honnen Over a year ago

+1 for showing way to solve the problem. Alejandro, I have one question: I think the XSLT 2.0 solution with group-adjacent="boolean(self::struct)" will only work with an XSLT processor that automatically strips white space text nodes (like AltovaXML Tools does) or if you add <xsl:strip-space elements="*"/> to the code. In both cases I think you also need <xsl:output indent="yes"/> to get readable and indented output, as you posted. Have you deliberately ignored that to keep the samples short or are you working with some tool/editor which does the indenting automatically?

user357812 Over a year ago

@Martin Honnen: You are right about stripping whitespace only text nodes, I was using Altova, editing now. About identation: a never pay attention to xsl:output/@indent because every processor does what it wants and because in production I would never use identation.

Flack Over a year ago

@Alejandro. +1 for no indentaion in production.

user612834 Over a year ago

Hi, thanks for the great answer. I have another problem here. What happens if the struct structure exists elswhere in the tree?

user357812 Over a year ago

@user612834: XSLT 1.0 answer will group in any hierarchy level. Fixing XSLT 2.0 solution according.

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