Transforming an XML file to another XML file using XSLT

Question

I have a simple xml file I would like to transform using XSLT.

The first node is the schema(header), the following nodes are the actual data. Notice that there are some missing fields in the data.

<ex:file xmlns:ex="http://example.com">
  <ex:header>
    <ex:title>houseNumber</ex:title>
    <ex:title>street</ex:title>
    <ex:title>city</ex:title>
    <ex:title>state</ex:title>
  </ex:header>
  <ex:address>
    <ex:field>108</ex:field>
    <ex:field>Ridgewood Circle</ex:field>
    <ex:field>Rochester</ex:field>
    <ex:field>NY</ex:field>
  </ex:address>
  <ex:address>
    <ex:field/>
    <ex:field>W. Clark</ex:field>
    <ex:field>Springfield</ex:field>
    <ex:field>IL</ex:field>
  </ex:address>
</ex:file>

We would like to transform this XML in two ways. First, we want to use the information in the "header" and substitute the four ex:field elements, in such a way I can get an XML that looks like:

<ex:file xmlns:ex="http://example.com">
  <ex:header>
    <ex:title>houseNumber</ex:title>
    <ex:title>street</ex:title>
    <ex:title>city</ex:title>
    <ex:title>state</ex:title>
  </ex:header>
  <ex:address>
    <ex:houseNumber>108</ex:houseNumber>
    <ex:street>Ridgewood Circle</ex:street>
    <ex:city>Rochester</ex:city>
    <ex:state>NY</ex:state>
  </ex:address>
  <ex:address>
    <ex:houseNumber/>
    <ex:street>W. Clark</ex:street>
    <ex:city>Springfield</ex:city>
    <ex:state>IL</ex:state>
  </ex:address>
</ex:file>

The second transformation is to eliminate those empty element:

<ex:file xmlns:ex="http://example.com">
  <ex:header>
    <ex:title>houseNumber</ex:title>
    <ex:title>street</ex:title>
    <ex:title>city</ex:title>
    <ex:title>state</ex:title>
  </ex:header>
  <ex:address>
    <ex:houseNumber>108</ex:houseNumber>
    <ex:street>Ridgewood Circle</ex:street>
    <ex:city>Rochester</ex:city>
    <ex:state>NY</ex:state>
  </ex:address>
  <ex:address>
    <ex:street>W. Clark</ex:street>
    <ex:city>Springfield</ex:city>
    <ex:state>IL</ex:state>
  </ex:address>
</ex:file>

Notice that the "houseNumber" in the second "record" is gone.

I have gone through the XSLT tutorial ( http://www.w3schools.com/xsl/default.asp ) several times and I am not sure if this can be actually done.

Thanks in advance to all.

Answer 1

The following transformation solves your first problem. It is an identity transform with one additional template that specifies what should be done to each ex:field element.

XSLT Stylesheet

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:ex="http://example.com">

    <xsl:output method="xml" indent="yes"/>
    <xsl:strip-space elements="*"/>

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

    <xsl:template match="ex:address">
        <xsl:copy>
            <xsl:for-each select="ex:field">
            <xsl:variable name="pos" select="position()"/>
                <xsl:element name="{concat('ex:',../../ex:header/ex:title[position() = $pos])}">
                    <xsl:apply-templates select="@*|node()"/>
                </xsl:element>
            </xsl:for-each>
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

XML Output

<?xml version="1.0" encoding="utf-8"?>
<ex:file xmlns:ex="http://example.com">
   <ex:header>
      <ex:title>houseNumber</ex:title>
      <ex:title>street</ex:title>
      <ex:title>city</ex:title>
      <ex:title>state</ex:title>
   </ex:header>
   <ex:address>
      <ex:houseNumber>108</ex:houseNumber>
      <ex:street>Ridgewood Circle</ex:street>
      <ex:city>Rochester</ex:city>
      <ex:state>NY</ex:state>
   </ex:address>
   <ex:address>
      <ex:houseNumber/>
      <ex:street>W. Clark</ex:street>
      <ex:city>Springfield</ex:city>
      <ex:state>IL</ex:state>
   </ex:address>
</ex:file>

---

To also exclude empty input elements, it is better to reformulate the above for-each as a separate template matching ex:field elements. Then, add a second template that matches ex:field elements if they do not contain any text.

XSLT Stylesheet

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:ex="http://example.com">

    <xsl:output method="xml" indent="yes"/>
    <xsl:strip-space elements="*"/>

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

    <xsl:template match="ex:field">
        <xsl:variable name="pos" select="position()"/>
                <xsl:element name="{concat('ex:',../../ex:header/ex:title[position() = $pos])}">
                    <xsl:apply-templates select="@*|node()"/>
                </xsl:element>
    </xsl:template>

    <xsl:template match="ex:field[not(text())]"/>

</xsl:stylesheet>

Final XML Output

<?xml version="1.0" encoding="utf-8"?>
<ex:file xmlns:ex="http://example.com">
   <ex:header>
      <ex:title>houseNumber</ex:title>
      <ex:title>street</ex:title>
      <ex:title>city</ex:title>
      <ex:title>state</ex:title>
   </ex:header>
   <ex:address>
      <ex:houseNumber>108</ex:houseNumber>
      <ex:street>Ridgewood Circle</ex:street>
      <ex:city>Rochester</ex:city>
      <ex:state>NY</ex:state>
   </ex:address>
   <ex:address>
      <ex:street>W. Clark</ex:street>
      <ex:city>Springfield</ex:city>
      <ex:state>IL</ex:state>
   </ex:address>
</ex:file>