Apache Xalan project has released XalanJ 2.7.3 few days ago, and I thought to write couple of blog posts here, to report on the basic sanity of XalanJ 2.7.3's functional quality.
Following is a simple XML transformation requirement.
XML input document :
<?xml version="1.0" encoding="UTF-8"?>
<elem>
<a>2</a>
<a>3</a>
<a>5</a>
<a>1</a>
<a>7</a>
<a>4</a>
</elem>
We need to write an XSLT 1.0 stylesheet, that outputs the maximum value from the list of XML "a" elements mentioned within above cited XML document.
Following are the three XSLT 1.0 stylesheets that I've come up with, that do this correctly,
1)
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exslt="http://exslt.org/common"
version="1.0">
<xsl:output method="text"/>
<xsl:template match="/elem">
<xsl:variable name="temp">
<xsl:for-each select="a">
<xsl:sort select="." data-type="number" order="descending"/>
<e1><xsl:value-of select="."/></e1>
</xsl:for-each>
</xsl:variable>
<xsl:value-of select="concat('Maximum : ', exslt:node-set($temp)/e1[1])"/>
</xsl:template>
</xsl:stylesheet>
2)
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exslt="http://exslt.org/common"
version="1.0">
<xsl:output method="text"/>
<xsl:template match="/elem">
Maximum : <xsl:call-template name="findMax"/>
</xsl:template>
<xsl:template name="findMax">
<xsl:variable name="temp">
<xsl:for-each select="a">
<xsl:sort select="." data-type="number" order="descending"/>
<e1><xsl:value-of select="."/></e1>
</xsl:for-each>
</xsl:variable>
<xsl:value-of select="exslt:node-set($temp)/e1[1]"/>
</xsl:template>
</xsl:stylesheet>
3)
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="text"/>
<xsl:template match="/elem">
<xsl:choose>
<xsl:when test="count(a) = 0"/>
<xsl:when test="count(a) = 1">
Maximum : <xsl:value-of select="a[1]"/>
</xsl:when>
<xsl:otherwise>
<xsl:variable name="result">
<xsl:call-template name="findMax">
<xsl:with-param name="curr_max" select="a[1]"/>
<xsl:with-param name="next_node" select="a[2]"/>
</xsl:call-template>
</xsl:variable>
Maximum : <xsl:value-of select="$result"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template name="findMax">
<xsl:param name="curr_max"/>
<xsl:param name="next_node"/>
<xsl:choose>
<xsl:when test="$next_node/following-sibling::*">
<xsl:choose>
<xsl:when test="number($next_node) > number($curr_max)">
<xsl:call-template name="findMax">
<xsl:with-param name="curr_max" select="$next_node"/>
<xsl:with-param name="next_node" select="$next_node/following-sibling::*[1]"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:call-template name="findMax">
<xsl:with-param name="curr_max" select="$curr_max"/>
<xsl:with-param name="next_node" select="$next_node/following-sibling::*[1]"/>
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:when>
<xsl:otherwise>
<xsl:choose>
<xsl:when test="number($next_node) > number($curr_max)">
<xsl:value-of select="$next_node"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$curr_max"/>
</xsl:otherwise>
</xsl:choose>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
I somehow, personally like the XSLT solution 3) illustrated above, for these requirements. This solution, traverses the sequence of XML "a" elements till the end of "a" elements list, and outputs the maximum value from the list at the end of XML elements traversal. This solution, seems to have an algorithmic time complexity of O(n), with a little bit of possible overhead of XSLT recursive template calls than the other two XSLT solutions.
The XSLT solutions 1) and 2) illustrated above, seem to have higher algorithmic time complexity than solution 3), due to the use of XSLT xsl:sort instruction (which probably has algorithmic time complexity of O(n * log(n)) or O(n * n)). The XSLT solutions 1) and 2) illustrated above, also seem to have higher algorithmic "space complexity" (this measures the memory used by the algorithm) due to storage of intermediate sorted result.
The XalanJ command line, to run above cited XSLT transformations are following,
java org.apache.xalan.xslt.Process -in file.xml -xsl file.xsl
