Question

I am using XSLT to convert a very large XML document into (X)HTML. For some of the tags I am converting them to a <div>. I would like to be able to create a unique id for these tags, using an incremented integer to form part of the unique id.

An example of the rule I am using is:

<xsl:template match="bookcoll/book">
    <div class="book">
        <xsl:apply-templates/>
    </div>
</xsl:template>

This XSLT template is working nicely. What I would now like to have is the tag:

<div class="book">;  

becoming:

<div class="book" id="book-[COUNTER-VALUE]">  

Ideally the counter would start from 1, not 0.

I don’t know if it makes much difference, I am using the Java packages javax.xml.parsers and javax.xml.transform to perform the actual transformation. I am a bit of an XSLT noob, so if there’s any pertinent information I’ve missed please let me know.

How could this be achieved in XSLT?

Answer 1

The natural/idiomatic/failsafe solution would be:

<div class="book" id="book-{generate-id()}">

It’s not incrementing, but it’s guaranteed to be unique. And it’s going to produce HTML-valid ID strings (name tokens).

EDIT: If it must be incrementing, do something like the following:

<!-- in the calling template… -->
<xsl:apply-templates select="bookcoll/book[xpath to filter them if necessary]" />

<!-- …later -->
<xsl:template match="bookcoll/book">
  <div class="book" id="book-{position()}">
    <xsl:apply-templates/>
  </div>
</xsl:template>

You can use format-number() to adapt the output of position() to your needs.

position() will return the node position relative to the “batch” that is currently being processed. With an explicit call to <xsl:apply-templates> you make sure that they are numbered the way you want.