The template I used in the previous section applied to only one
node-the root node-and performed a trivial action, replacing the
entire XML document with an HTML document. However, you can also
apply templates to the children of a node that you've matched, and
you do that with the <xsl:apply-templates> element.
For example, say that I want to convert planets.xml to HTML. The
document node in that document is <PLANETS>, so I can match
that element with a template, setting the match attribute to the name
of the element I want to match. Then I replace the <PLANETS>
element with an <HTML> element, like this:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="PLANETS">
<HTML>
.
.
.
</HTML>
</xsl:template>
.
.
.
</xsl:stylesheet>
But what about the children of the <PLANETS> element? To
make sure that they are transformed correctly, you use the
<xsl:apply-templates> element this way:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="PLANETS">
<HTML>
<xsl:apply-templates/>
</HTML>
</xsl:template>
.
.
.
</xsl:stylesheet>
Now you can provide templates for the child nodes. In this case,
I'll just replace each of the three <PLANET> elements with some
text, which I place directly into the template for the <PLANET>
element:
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="PLANETS">
<HTML>
<xsl:apply-templates/>
</HTML>
</xsl:template>
<xsl:template match="PLANET">
<P>
Planet data will go here....
</P>
</xsl:template>
</xsl:stylesheet>
And that's it; now the <PLANETS> element is replaced by an
<HTML> element, and the <PLANET> elements are also
replaced:
<HTML>
<P>
Planet data will go
here....
</P>
<P>
Planet data will go
here....
</P>
<P>
Planet data will go
here....
</P>
</HTML>
You can see that this transformation works, but it's still less
than useful; all we've done is replace the <PLANET> elements
with some text. What if we wanted to access some of the data in the
<PLANET> element? For example, say that we wanted to place the
text from the <NAME> element in each <PLANET> element in
the output document:
<PLANET>
<NAME>Mercury</NAME>
<MASS UNITS="(Earth
= 1)">.0553</MASS>
<DAY
UNITS="days">58.65</DAY>
<RADIUS
UNITS="miles">1516</RADIUS>
<DENSITY
UNITS="(Earth = 1)">.983</DENSITY>
<DISTANCE
UNITS="million miles">43.4</DISTANCE><!--At
perihelion-->
</PLANET>
To gain access to this kind of data, you can use the select
attribute of the <xsl:value-of> element.
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