Question on Apply Template

vvenk · July 10th, 2008, 11:39 AM

As suggested by one of you, I went through the Tutorials on XSLT.

I got confused when I got to the section on <xsl:apply-templates>.

In the example they have for the section:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
  <html>
   <body>
    <h2>My CD Collection</h2>
    <xsl:apply-templates/>
   </body>
  </html>
</xsl:template>

<xsl:template match="cd">
  <p>
  <xsl:apply-templates select="title"/>
  <xsl:apply-templates select="artist"/>
  </p>
</xsl:template>

<xsl:template match="title">
  Title: <span style="color:#ff0000">
           <xsl:value-of select="."/>
         </span>
         <br />
</xsl:template>
<xsl:template match="artist">
  Artist: <span style="color:#00ff00">
  <xsl:value-of select="."/></span>
  <br />
</xsl:template>
</xsl:stylesheet>

What makes it print all the Titles and Artists in the XML file without a <xsl:for-each> element?

Also, with only the first occurence of <xsl:template> element, it dumps the contents of the XML file after printing the heading "My CD Collection".

Venki

Venki

Venki · July 10th, 2008, 11:46 AM

hello Vvenk, can you show the XMl file that you for the example and the output from the xslt ? so that i can help you.

Venki

Martin Honnen · July 10th, 2008, 11:49 AM

Processing starts for the root node /, that template creates the html element with a body child element and a h2 child element of the body and inside the body element has an xsl:apply-templates that processes all child nodes of the root node. The single child node of the root node is the catalog element, as the stylesheet contains no matching template the built-in template is used which simply processes the child nodes of the catalog element. Those are the cd elements and that way the template matching the cd elements is applied to each cd element. That template outputs a p element and applies the templates for title and artist.

--
Martin Honnen
Microsoft MVP - XML

vvenk · July 10th, 2008, 11:50 AM

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/xsl" href="cdcatalog_apply.xsl"?>

<catalog>
    <cd>
        <title>Empire Burlesque</title>
        <artist>Bob Dylan</artist>
        <country>USA</country>
        <company>Columbia</company>
        <price>10.90</price>
        <year>1985</year>
    </cd>
    <cd>
        <title>Hide your heart</title>
        <artist>Bonnie Tyler</artist>
        <country>UK</country>
        <company>CBS Records</company>
        <price>9.90</price>
        <year>1988</year>
    </cd>
</catalog>

Venki

Venki · July 10th, 2008, 11:59 AM

yes vvenk, to have exp simple , the line

<xsl:template match="cd">

in your code makes to print all "title" and "Artist" which is the child of "cd" node.
the line
<xsl:template match="cd">
looks for all node with the node name "cd" and once it matches the node ,it applies the template.

As martin said they are choosing the entire xml document using <xsl:template match="/"> by the selecting the root element "/"

let me know if you have any further questions.

Venki

Martin Honnen · July 10th, 2008, 12:10 PM

Venki, your explanation is not correct. / selects respectively matches the root node (the document node) which is quite different from the root element selected by /* (or /catalog in case of the sample document).
So don't confuse the root node with the root element.

--
Martin Honnen
Microsoft MVP - XML

mhkay · July 10th, 2008, 12:21 PM

xsl:apply-templates selects one or more nodes and tosses them into the air, saying "is anyone interested in these?". Around the playing field are lots of template rules, all waiting for nodes to be thrown into the air. When one of them sees a node that it fancies, it catches it and does the action called for, which will often involve selecting some further nodes and throwing them in the air, a process which carries on until the processing is complete.

The beauty of the mechanism lies in the loose coupling: the rule that throws a node in the air doesn't know who will catch it, and the rule that catches it doesn't know who threw it. This makes template rules highly reusable, and highly adaptable to documents with variable or unpredictable structure.

If xsl:apply-templates is written with no select attribute (a common case) then it selects all the children of the current node. If all the template rules do this, the effect is a recursive walk of the entire document tree, each node being processed by the best matching template rule.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Venki · July 10th, 2008, 12:21 PM

Quote:

quote:Originally posted by Martin Honnen
Venki, your explanation is not correct. / selects respectively matches the root node (the document node) which is quite different from the root element selected by /* (or /catalog in case of the sample document).
So don't confuse the root node with the root element.

--
Martin Honnen
Microsoft MVP - XML

thank you Martin for correcting me...still some confusion persists between node and element..
to clear this can you give some exp or example in specific to differentiate this two.

Venki