XSLT, 2nd Edition

[2.0] The collection() Function

The collection() function takes a string as its argument and returns a collection of nodes. Defined as part of the XPath 2.0 spec, it gives us the ability to use a URI to retrieve a collection of documents. How those documents are stored (or whether they’re really documents at all) is implementation-dependent. In particular, the spec mentions accessing data in a relational database as a possible implementation of the collection() function. The fact that the string passed to the function can be generated and can contain parameters makes collection() very flexible.

We’ll look at a short example here. Here’s the document we’ll pass to the collection() function:

<?xml version="1.0"?>
<!-- polist.xml -->
<collection>
  <doc href="po38292.xml"/>
  <doc href="po38293.xml"/>
  <doc href="po38294.xml"/>
  <doc href="po38295.xml"/>
</collection>

This is very similar to the list of purchase orders we worked with earlier in this chapter. The stylesheet that invokes the collection() function looks like this:

<?xml version="1.0"?>
<!-- collection.xsl -->
<xsl:stylesheet version="2.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  
  <xsl:output method="text"/>

  <xsl:template match="/">
    <xsl:text>&#xA;A test of the collection() function:</xsl:text>

    <xsl:variable name="docPile" as="node()*"
      select="collection('polist.xml')"/>

    <xsl:text>&#xA;&#xA;  The customers in the </xsl:text>
    <xsl:text>collection are: &#xA;    </xsl:text>
 <xsl:for-each select="$docPile/purchase-order/customer"> ...