Michael Kay schrieb:
As David suggests, I think I'd go for the approach of generating a
stylesheet. In effect your <REPORT_FORMAT> element defines a miniature
programming language, and a good way of implementing such languages is
often to translate them to XSLT. I've done similar things with report
specifications entered interactively on the screen. You're already
doing dynamic construction/evaluation of XPath expressions, so dynamic
construction of the entire stylesheet (or of the controlling
framework, it can always include/import a fixed module) isn't a major
step from that.
I don't have the code to generate the stylesheet, but I'd like to
propose what I imagine the result should look like.
There is a string representation of the sorting order, captured in the
xsl:variable $order. Then there is one generated matching template for
each value of $order that may occur in reality. (Well, I didn't write
the code to generate these templates, so I hand-coded one and left the
rest up to imagination.) And there is a template to format the output
(the copy template). Auto-generated stuff should go in one module,
hand-coded stuff in the other one.
Surely, this could be improved. Any comments welcome.
Two stylesheets and XML data follow.
Michael Ludwig
mludwig(_at_)forelle:~/Werkstatt/xsl > expand -t2 Sapir-2008-05-22.xsl
<xsl:transform version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<xsl:import href="Sapir-sorting.xsl"/>
<xsl:template match="REPORT">
<xsl:copy>
<ORDER-USED><xsl:value-of select="$order"/></ORDER-USED>
<xsl:apply-templates select="*"/>
</xsl:copy>
</xsl:template>
</xsl:transform>
mludwig(_at_)forelle:~/Werkstatt/xsl > expand -t2 Sapir-sorting.xsl
<xsl:transform version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<!-- Generate this module to include all needed permutations
of your sort parameters. Hopefully, not too many! -->
<!-- sorting criteria identifier; normalize by eliminating spaces -->
<xsl:variable name="order"
select="translate(/REPORT/REPORT_FORMAT/ORDER_BY, ' ', '')"/>
<!-- just the copy template to generate output -->
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
<!-- sorting templates; should be generated -->
<xsl:template match="X[ $order = 'DATE,ID_1,ID_2,TYPE' ]">
<xsl:copy>
<xsl:apply-templates select="X_ROW">
<xsl:sort select="DATE"/>
<xsl:sort select="ID_1"/>
<xsl:sort select="ID_2"/>
<xsl:sort select="TYPE"/>
</xsl:apply-templates>
</xsl:copy>
</xsl:template>
<!-- more of these -->
</xsl:transform>
mludwig(_at_)forelle:~/Werkstatt/xsl > expand -t2 Sapir-2008-05-22.xml
<REPORT>
<REPORT_HDR>...</REPORT_HDR>
<REPORT_FORMAT>
<ORDER_BY>DATE, ID_1, ID_2, TYPE</ORDER_BY>
<PARENT_NODE>X</PARENT_NODE>
<CHILD_NODE>X_ROW</CHILD_NODE>
</REPORT_FORMAT>
<X>
<X_ROW>
<DATE>2008-05-25</DATE>
<ID_1>14</ID_1>
<TYPE>A</TYPE>
</X_ROW>
<X_ROW>
<DATE>2008-05-19</DATE>
<ID_1>3</ID_1>
<TYPE>B</TYPE>
</X_ROW>
<X_ROW>
<DATE>2008-05-29</DATE>
<ID_1>2</ID_1>
<TYPE>A</TYPE>
</X_ROW>
<X_ROW>
<DATE>2008-05-22</DATE>
<ID_1>6</ID_1>
<TYPE>C</TYPE>
</X_ROW>
</X>
</REPORT>
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