XPath to convert child elements to single line list

Question

I need XPath code to take child elements (one or more) and put them on a single line, separated by commas.

So if I have the following XML:

<Authors>
  <Author>Bob Smith</Author>
  <Author>Mary Jones</Author>
  <Author>Sam Doe</Author>
</Authors>

I want the following output:

Bob Smith, Mary Jones, Sam Doe

It needs to be smart enough to leave of the comma of the last author. And there might be only one author.

Much thanks

Answer 1

XPath isn't a transformation tool so you can't use it alone to do what you want. You might be thinking of XSL, which uses XPath and is capable of transforming data.

An XPath expression that can pull data from your XML example would be

/Authors/Author

Then in whatever it is that you're using to execute the XPath expression on the document (be it XSL or some XML library) you can loop over the result and create the output you need.

In XSL you could do something along these lines:

<xsl:for-each select="/Authors/Author">
  <xsl:if test="position() != 1">
    <xsl:text>, </xsl:text>
  </xsl:if>
  <xsl:value-of select="text()"/>
</xsl:for-each>

Other languages would be more straightforward, likely using the language's join function, if it has one.