XSLT - append sibling

Question

I'm trying to use XSLT to append context-param as last sibling. There's no common parent element so the task is a little bit harder.

I'd like to append following element:

<context-param>
    <param-name>miku</param-name>
    <param-value>kawaii</param-value>
</context-param>

as the last context-param element (eg. all context-param elements must be next to each other, they can't be scattered anywhere in xml) in following xml:

<web-app>
  <not_interesting_element1/>
  <not_interesting_element2/>

  <context-param>
    <param-name>not_interesting_param_key1</param-name>
    <param-value>kawaii</param-value>
  </context-param>
  <context-param>
    <param-name>not_interesting_param_key2</param-name>
    <param-value>kawaii</param-value>
  </context-param>
  <context-param>
    <param-name>parameterThatsGuaranteedToBeHere</param-name>
    <param-value>someValue</param-value>
  </context-param>


  <not_interesting_element3/>
  <not_interesting_element4/>
  <!-- ... servlets, ... -->
</web-app>

The result should look like this:

<web-app>
  <not_interesting_element1/>
  <not_interesting_element2/>

  <context-param>
    <param-name>not_interesting_param_key1</param-name>
    <param-value>kawaii</param-value>
  </context-param>
  <context-param>
    <param-name>not_interesting_param_key2</param-name>
    <param-value>kawaii</param-value>
  </context-param>
  <context-param>
    <param-name>parameterThatsGuaranteedToBeHere</param-name>
    <param-value>someValue</param-value>
  </context-param>
  <context-param>
      <param-name>miku</param-name>
      <param-value>kawaii</param-value>
  </context-param>

  <not_interesting_element3/>
  <not_interesting_element4/>
  <!-- ... servlets, ... -->
</web-app>

How could I do it please?

Answer 1

This transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:param name="pElemToAdd">
    <context-param>
        <param-name>miku</param-name>
        <param-value>kawaii</param-value>
    </context-param>
 </xsl:param>

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

 <xsl:template match="context-param[last()]">
  <xsl:call-template name="identity"/>
  <xsl:copy-of select="$pElemToAdd"/>
 </xsl:template>
</xsl:stylesheet>

when applied to the provided XML document:

<web-app>
    <not_interesting_element1/>
    <not_interesting_element2/>
    <context-param>
        <param-name>not_interesting_param_key1</param-name>
        <param-value>kawaii</param-value>
    </context-param>
    <context-param>
        <param-name>not_interesting_param_key2</param-name>
        <param-value>kawaii</param-value>
    </context-param>
    <context-param>
        <param-name>parameterThatsGuaranteedToBeHere</param-name>
        <param-value>someValue</param-value>
    </context-param>
    <not_interesting_element3/>
    <not_interesting_element4/>
    <!-- ... servlets, ... -->
</web-app>

produces the wanted, correct result:

<web-app>
   <not_interesting_element1/>
   <not_interesting_element2/>
   <context-param>
      <param-name>not_interesting_param_key1</param-name>
      <param-value>kawaii</param-value>
   </context-param>
   <context-param>
      <param-name>not_interesting_param_key2</param-name>
      <param-value>kawaii</param-value>
   </context-param>
   <context-param>
      <param-name>parameterThatsGuaranteedToBeHere</param-name>
      <param-value>someValue</param-value>
   </context-param>
   <context-param>
      <param-name>miku</param-name>
      <param-value>kawaii</param-value>
   </context-param>
   <not_interesting_element3/>
   <not_interesting_element4/><!-- ... servlets, ... -->
</web-app>

Explanation:

1. The identity rule copies every node "as-is".

2. There is a single template, overriding the identity template. This template matches the last context-param element of all context-param elements that are children of their parent.

3. In the overriding template two actions are performed; the current node is copied by a call to the identity rule; then the element to be appended is copied to the output. For convenience and flexibility, we assume that the element to be appended is passed as a parameter to the transformation.