Can we Create a Sequence in XSLT? - xslt

Question

I am generating a text file using xslt.when i pass the xml input the xslt is converting the xml input as text file.can we provide the sequence number for each invocation.
and store it in some variable.
1)If suppose for the first time execution one text file is created so there is a variable inside the xslt (<sequence>) it should assign as number 1 like below
<sequence>1</sequence>
2)for the second time execution one more text file is created so the the sequence variable should increase.
<sequence>2<sequence>
3)for the third time execution one more text file is created so the sequence becomes like this
<sequence>3</sequence>
This thing we can generally do by create a sequence in oracle database and call that sequence inside the xslt and for each execution the sequence get increased
<sequence>CallOracleSequence</sequence>
can anyone please suggest with out using Oracle sequence.can we handle this inside the xslt.

Answer 1

The XSLT will not maintain state between executions of the transforms.
One option would be to leverage an external config file that contains the sequence number. Using an entity reference, you can make that XML config part of the XSLT document to read it's current value and when the XSLT executes, increment the number and overwrite the config file with the new sequence number using <xsl:result-document>.
Below is a working example of an XSLT 2.0 stylesheet that assumes there is a sequence file called sequence.xml in the same directory as the XSLT being executed:
<?xml version="1.0" encoding="UTF-8"?>
<!--delare entities to reference the sequence file-->
<!DOCTYPE xsl:stylesheet [
<!ENTITY sequenceFile SYSTEM "sequence.xml">
]>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:output name="sequenceOutput" method="xml" indent="yes"/>
<!--this variable is used to store the expanded entity reference for
the current sequence.xml file
When the XSLT is parsed it will "look" like this to the XML parser:
<xsl:variable name="sequence><sequence>1</sequence></xsl:variable>
-->
<xsl:variable name="sequence">
<!--
this entity reference will expand to:
<sequence>x</sequence>
when the XSLT is parsed
-->
&sequenceFile;
</xsl:variable>
<!--
Use the document() function with an empty value to read the XSLT
and then parse the sequence value produced by the entity reference
-->
<xsl:variable name="currentSequenceValue"
select="number(document('')/*/xsl:variable[#name='sequence']/sequence)"/>
<xsl:template match="/">
<!--do normal processing of the XML document-->
<xsl:apply-templates />
<!--
This will overwrite the sequence file with the incremented value
-->
<xsl:result-document format="sequenceOutput" href="sequence.xml">
<sequence><xsl:value-of select="$currentSequenceValue+1"/></sequence>
</xsl:result-document>
</xsl:template>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>

Answer 2

Usually the sequence number will relate to something in the input, so you can use position() or xsl:number. But the details depend on the structure of the input.

Answer 3

This can be achieved with a single XSLT 2.0 transformation by writing out two files -- the result of the transformation and the updated number of executions:
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:variable name="vRepetitions" select=
"document('file:///c:/temp/delete/numberOfRepetitions.xml')/* +1"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="/">
<xsl:result-document
href="file:///c:/temp/delete/iteration{$vRepetitions}.xml">
<xsl:apply-templates/>
</xsl:result-document>
<xsl:result-document href="file:///c:/temp/delete/numberOfRepetitions.xml">
<n><xsl:value-of select="$vRepetitions"/></n>
</xsl:result-document>
</xsl:template>
</xsl:stylesheet>
There are two files involved: the source XML document and an file containing the current number of executions -- the latter must be initially created to contain:
<n>0</n>
When the above transformation is applied on any source XML document (for this demo it just applies the identity rule on it), it does its usual processing and produces the wanted result. Additionally, the transformation reads the XML document that contains the current number of executuions and updates this number and writes the updated (number of executions) document back to disk:
Saxon 9.1.0.5J from Saxonica
Java version 1.6.0_31
Stylesheet compilation time: 625 milliseconds
Processing file:/C:/Program%20Files/Java/jre6/bin/marrowtr.xml
Building tree for file:/C:/Program%20Files/Java/jre6/bin/marrowtr.xml using class net.sf.saxon.tinytree.TinyBuilder
Tree built in 16 milliseconds
Tree size: 4 nodes, 4 characters, 0 attributes
Loading net.sf.saxon.event.MessageEmitter
Building tree for file:///c:/temp/delete/numberOfRepetitions.xml using class net.sf.saxon.tinytree.TinyBuilder
Tree built in 0 milliseconds
Tree size: 4 nodes, 1 characters, 0 attributes
Writing to file:/c:/temp/delete/iteration2.xml
Writing to file:/c:/temp/delete/numberOfRepetitions.xml
Execution time: 140 milliseconds
Memory used: 11477344
NamePool contents: 16 entries in 16 chains. 6 prefixes, 7 URIs
Here we see that at the second execution the transformation creates two files:
iteration2.xml contains the result from the second execution of the transformation.
numberOfRepetitions.xml If we examine this file, its contents after the second execution is as expected:
. . . .
<n>2</n>