How to use only distinct values within XSLT for-each loop - xslt

Question

I am trying to retrieve only distinct values of an element. This is my XML:
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cF">
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
<property key="MeterClassTypeCode" value="cF"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cE">
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
<property key="MeterClassTypeCode" value="cE"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cC">
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
<property key="MeterClassTypeCode" value="cC"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cD">
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
<property key="MeterClassTypeCode" value="cD"/>
</LaunchedMeterClass>
I want to create an XPath to get only those "LaunchedMeterClass" nodes having an unique value for <property key="ClusterContractUUID">. At the moment, I am using the following:
<xsl:for-each select="./descendant::LaunchedMeterClass">
<xsl:choose>
<xsl:when test="./property/#key='ClusterContractUUID'">
<contract-type>
<property>
<xsl:attribute name="key">ClusterContractUUID</xsl:attribute>
<xsl:attribute name="value">
<xsl:value-of select="./property[#key='ClusterContractUUID']/#value"/>
</xsl:attribute>
</property>
</contract-type>
</xsl:when>
<xsl:otherwise>
<contract-type>
<property>
<xsl:attribute name="key">contractTypeCategory</xsl:attribute>
</property>
</contract-type>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each>
But this gives me all the elements including duplicates:
<contract-type>
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
</contract-type>
<contract-type>
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
</contract-type>
<contract-type>
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
</contract-type>
<contract-type>
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
</contract-type>
How can I write an XPath which gives only distinct values? My desired output is:
<contract-type>
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
</contract-type>
<contract-type>
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
</contract-type>
Thank you in advance for your help!

Answer 1

Try this:
XML:
<root>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cF">
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
<property key="MeterClassTypeCode" value="cF"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cE">
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
<property key="MeterClassTypeCode" value="cE"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cC">
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
<property key="MeterClassTypeCode" value="cC"/>
</LaunchedMeterClass>
<LaunchedMeterClass id="584e348b-2a06-42d0-a858-b8909f579238-St-4M-Template-Standard-cD">
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
<property key="MeterClassTypeCode" value="cD"/>
</LaunchedMeterClass>
</root>
XSLT2.0
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:template match="root">
<xsl:for-each select="distinct-values(descendant::property[#key='ClusterContractUUID']/#value)">
<contract-type>
<property>
<xsl:attribute name="key">ClusterContractUUID</xsl:attribute>
<xsl:attribute name="value">
<xsl:value-of select="."/>
</xsl:attribute>
</property>
</contract-type>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
Result:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<contract-type>
<property key="ClusterContractUUID" value="c2cebd90-9265-4cea-8018-0aac6efcced2"/>
</contract-type>
<contract-type>
<property key="ClusterContractUUID" value="d0c9f440-172c-49ad-9b95-cddce23f16fa"/>
</contract-type>
</root>
Edit:
Edited to get following-sibling values. In above XSLT, template match is # attributes side, instead of that if template match at elements, we can access the other siblings, ancestors, descendants, etc, easily.
XSLT:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:output indent="yes"/>
<xsl:template match="#*|node()">
<xsl:copy><xsl:apply-templates select="#* | node()"/></xsl:copy>
</xsl:template>
<xsl:template match="root">
<root>
<xsl:for-each select="descendant::property[#key='ClusterContractUUID'
and not(#value=preceding::property[#key='ClusterContractUUID']/#value)]">
<contract-type>
<xsl:copy><xsl:apply-templates select="#*|node()"/></xsl:copy>
<xsl:apply-templates select="following-sibling::property"/>
</contract-type>
</xsl:for-each>
</root>
</xsl:template>
</xsl:stylesheet>

Answer 2

You can perhaps try exslt's set:distinct:
http://exslt.org/set/functions/distinct/
There's an example at the bottom. Your mileage may vary.

Answer 3

This is generally known as "grouping".
In XSLT 2.0, use the <xsl:for-each-group> construct.
In XSLT 1.0, use "Muenchian grouping" - you'll find that in your favourite XSLT textbook, or in online resources.
If you really need to do it in XPath rather than XSLT (your question is unclear) the best you can do is the XPath 2.0 distinct-values() function - there's nothing in XPath 1.0 that will help you much.