Question

I have the following simplified XML structure:

<?xml version="1.0" encoding="UTF-8"?>
<ExportData>
<TransportHeader>
    <Timestamp>2011-01-16 06:00:33</Timestamp>
    <From>
        <Name>DynamicExport</Name>
        <Version>1.</Version>
    </From>
    <MessageId>d7b5c5b69a83</MessageId>
</TransportHeader>
<ExportConfig>
    <DateTimeFormat>yyyy-MM-dd HH:mm:ss</DateTimeFormat>
    <DecimalSymbol>.</DecimalSymbol>
</ExportConfig>
<DataSet> 
    <Tables>
        <Table>
            <RH>...</RH>
            <Rows>
                <R>Data1</R>
                <R>Data2</R>
                <R>Data3</R>
                <R>Data4</R>
                <R>Data5</R>
            </Rows>
        </Table>
    </Tables>
</DataSet>
</ExportData>

I have to check if <R> elements exist or not. If no <R> elements exist the mapping has to be aborted, otherwise a <Line> element per <R> needs to be created.

I came up with this solution which works perfectly so far:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output encoding="ISO-8859-1" method="xml" indent="yes" />

<!-- suppress nodes that are not matched -->
<xsl:template match="text() | @*">
    <xsl:apply-templates select="text() | @*"/>
</xsl:template>

<xsl:template match="/">
    <xsl:choose>
        <xsl:when test="not(ExportData/DataSet/Tables/Table/Rows/node())">
            <xsl:message terminate="yes">No line items</xsl:message>
        </xsl:when>
        <xsl:otherwise>
            <xsl:apply-templates/>
        </xsl:otherwise>
    </xsl:choose>
</xsl:template>

<xsl:template match="/ExportData/DataSet/Tables/Table/Rows">
    <INVOIC02>
        <!-- apply LINE ITEMS template -->
        <xsl:apply-templates select="R"/>
    </INVOIC02>
</xsl:template>

<!-- Template creating LINE ITEMS -->
<xsl:template match="R">
    
    <Line>
        <elements></elements>
    </Line>
</xsl:template>


</xsl:stylesheet>

If there are <R> elements the output is this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<INVOIC02>
<Line>
    <elements/>
</Line>
<Line>
    <elements/>
</Line>
<Line>
    <elements/>
</Line>
<Line>
    <elements/>
</Line>
<Line>
    <elements/>
</Line>
</INVOIC02>

If there is just <Rows/> and no <R>s the mapping is aborted.

Now I have two questions:

-Is my test for <R> elements robust: test="not(ExportData/DataSet/Tables/Table/Rows/node())" ?

-I am using <xsl:apply-templates> to create the <Line> items instead of an <xsl:for-each> construct. Are my XPath expressions okay or could I make them better?

Answer 1

Is my test for elements robust: test=”not(ExportData/DataSet/Tables/Table/Rows/node())”
?

Well, do you want it to fail if there are no R elements, or fail if Rows does not have a child node(), which would include any element (not just R), text(), comment() or processing-instruction()?

If you really want to verify that there is at least one R element that is a child of Rows, you should adjust the test criteria to be more specific:

test="not(ExportData/DataSet/Tables/Table/Rows/R)"

Otherwise, it may pass that test and continue processing and not generate the content you want.

I am using <xsl:apply-templates> to create the <Line> items instead of an 
<xsl:for-each> construct. 
Are my XPath expressions okay or could I make them better?

You could get rid of the <xsl:if> conditional logic inside of your template for the root node and move that logic into a template for Rows that don’t contain R children. Putting logic into xsl:template @match criteria makes it easier for XSLT processors to optimize, which can lead to performance gains.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
    <xsl:output encoding="ISO-8859-1" method="xml" indent="yes" />

    <!-- suppress nodes that are not matched -->
    <xsl:template match="text() | @*">
        <xsl:apply-templates select="text() | @*"/>
    </xsl:template>

    <!--All Rows must contain an R.  
        If we encounter any that do not, terminate the transform -->
    <xsl:template match="/ExportData/DataSet/Tables/Table/Rows[not(R)]">
        <xsl:message terminate="yes">No line items</xsl:message>
    </xsl:template>

    <!--match for Rows that have R children -->
    <xsl:template match="/ExportData/DataSet/Tables/Table/Rows[R]">
        <INVOIC02>
            <!-- apply LINE ITEMS template -->
            <xsl:apply-templates select="R"/>
        </INVOIC02>
    </xsl:template>

    <!-- Template creating LINE ITEMS -->
    <xsl:template match="R">      
        <Line>
            <elements></elements>
        </Line>
    </xsl:template>

</xsl:stylesheet>