Order XML elements using XSLT

imshriram · June 30th, 2011, 01:59 AM

I have an XML with few elements and an XSD that tells the order in which the elements from the XML should appear.

Using XSLT, can I change the order of the elements in the XML to conform to the XSD?

samjudson · June 30th, 2011, 02:18 AM

I'm sure the answer is yes, but I suspect it would be some very complicated XSLT.

mhkay · June 30th, 2011, 05:33 AM

Let's split this into two steps: (a) extract from the XSD the order in which you want elements to appear, (b) do the reordering.

Let's start with (b). If we assume we're talking about a simple linear ordering (no choice or repetition) then it's not too difficult. Define the required order like this:

Code:

<xsl:variable name="order" as="element(*)>
  <name/><title/><description/><status/><asphyxiation/>
</xsl:variable>

and then sort your elements like this:

Code:

<xsl:perform-sort select="$input">
  <xsl:sort select="index-of($order/node-name(.), node-name(.))"/>
</xsl:perform-sort>

Stage (a), extracting information from a schema, is more difficult, and it all depends how clever you want to be (e.g, in handling choice and repetition, not to mention such things as types derived by extension or restriction, substitution groups, or the like.)

imshriram · July 1st, 2011, 03:26 AM

Hi Kay, Thanks for your reply. I am feeling better to know that this could be achieved in the first place.
But i am not able to get it to work:
Input:

Code:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <group>
        <element4>SomeValue4</element4>
      <element1>Changed1</element1>
      <element2>Changed2</element2>
      <element3>Changed3</element3>
    </group>
</root>

XSL:

Code:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output indent="yes"/>
 <xsl:variable name="order" as="element(*)">
  <element1/><element2/><element3/><element4/>
</xsl:variable>
<xsl:variable name="input" select="/" />
<xsl:template match="/">
<xsl:perform-sort select="$input">
  <xsl:sort select="index-of($order/node-name(.), node-name(.))"/>
</xsl:perform-sort>
</xsl:template>
</xsl:stylesheet>

But the output i get is

Code:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <group>
        <element4>SomeValue4</element4>
      <element1>Changed1</element1>
      <element2>Changed2</element2>
      <element3>Changed3</element3>
    </group>
</root>

I am not sure on what i am doing wrong.

mhkay · July 1st, 2011, 04:27 AM

You've set $input to a single node (the root node, '/'). There's not much point in sorting a sequence that contains only one node. Try

Code:

<xsl:variable name="input" select="/root/group/*" />

samjudson · July 1st, 2011, 05:36 AM

You also need to make the following change to the sort:

Code:

<xsl:sort select="index-of($order//node-name(.), node-name(.))"/>

imshriram · July 9th, 2011, 04:08 AM

Oops, I get the following error now,

A sequence of more than one item is not allowed as the value of variable $order (<element1/>, <element2/>, ...) ; SystemID: ; Line#: 9; Column#: -1

Martin Honnen · July 9th, 2011, 06:16 AM

Change

Code:

<xsl:variable name="order" as="element(*)">

to

Code:

<xsl:variable name="order" as="element()*">

imshriram · July 10th, 2011, 08:17 AM

You guys are awesome.
Kay, Martin Honnen and Samjudson. How do i close this thread as answered?

samjudson · July 10th, 2011, 10:56 AM

You can't mark a post as the 'answer' on here. I think you can click the 'Thanks' button for any post that is helpful though.