Question

I have XML documents which I want to transfer into another structure. An example of a document looks as follows:

<application>
    <contactPerson>
        <name>Dominik</name>
        <countryCode>DE</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Dorothea</name>
        <countryCode>DE</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Fiona</name>
        <countryCode>FR</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Fabian</name>
        <countryCode>FR</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Florian</name>
        <countryCode>FR</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Gabi</name>
        <countryCode>GB</countryCode>
    </contactPerson>
    <contactPerson>
        <name>Gert</name>
        <countryCode>GB</countryCode>
    </contactPerson>
</application>

Now what I want to do is group the elements by country, meaning the result should look like this:

<application>
    <memberState>
        <countryCode>De</countryCode>
        <contactPerson>
            <name>Dominik</name>
        </contactPerson>
        <contactPerson>
            <name>Dorothea</name>
        </contactPerson>
    </memberState>
    <memberState>
        <countryCode>FR</countryCode>
        <contactPerson>
            <name>Fiona</name>
        </contactPerson>
        <contactPerson>
            <name>Fabian</name>
        </contactPerson>
        <contactPerson>
            <name>Florian<name>
        </contactPerson>
    </memberState>
    <memberState>
        <countryCode>GB</countryCode>
        <contactPerson>
            <name>Gabi</name>
        </contactPerson>
        <contactPerson>
            <name>Gert</name>
        </contactPerson>
    </memberState>
</application>

I am using an XPath for-each pattern to select all countries, but it doesn’t do what it is supposed to do. My pattern looks as follows:

  <xsl:template match="/">
    <application>
      <xsl:for-each select="/application/contactPerson/countryCode[not(.=preceding-sibling::*/application/contactPerson/countryCode)]">
        <memberState>
          <countryCode>
            <xsl:value-of select="."/>
          </countryCode>
          <contactPerson>
            <name>
              <xsl:value-of select="../name"/>
            </name>
          </contactPerson>
        </memberState>
      </xsl:for-each>
    </application>
  </xsl:template>

The error is probably somewhere in the XPath expression which does not compile. I changed it to the following

<xsl:for-each select="/application/contactPerson/countryCode[not(.=preceding-sibling::*)]">

because I think I am already at the right position of my tree. This solution compiles, but it doesn’t give me a unique list of countries as I intended by using “preceding-sibling” but the complete list instead.

Besides that I need the solution to my problem, I would be especially thankful for some help on understanding what is actually happening here.

1. Is it possible to give a relative path as in my second solution or do I have to give the complete path each time?
2. Am I on the right track for making a unique list of country codes, or would that generally be implemented differently?
3. Is the solution I am looking for actually implementable with XSLT?

I appreciate your help very much.

Answer 1

Your XPath expression was almost correct:

<xsl:for-each 
    select="/application/contactPerson/countryCode[not(.=preceding-sibling::*)]"> 

The reason it didn’t work is that countryCode doesn’t have any siblings. To find the previous countryCodes, you need to move up one level and then back down:

<xsl:for-each 
    select="/application/contactPerson/countryCode[not(. = ../preceding-sibling::*/countryCode)]"> 

I believe that should successfully iterate through the distinct countryCodes.

This modification to your template should work. You needed another loop to iterate through all the people for each country:

<xsl:template match="/">
    <application>
      <xsl:for-each select="/application/contactPerson/countryCode[not(.=../preceding-sibling::*/countryCode)]">
        <memberState>
          <countryCode>
            <xsl:value-of select="."/>
          </countryCode>
          <xsl:for-each select="/application/contactPerson[countryCode = current()]">
          <contactPerson>
            <name>
              <xsl:value-of select="name"/>
            </name>
          </contactPerson>
          </xsl:for-each>
        </memberState>
      </xsl:for-each>
    </application>
  </xsl:template>