Copying all XML elements and updating one of them in XSL - xslt

Question

I have a requirement in my project some thing like this,
I have to copy all the elements from an xml and for few elements I have to update if present else I have to add it.
For example in the below xml I have an element Extrensic name "taxIncluded"> , in translated xml I want the value of it be updated.If it is missing I have to include it.
input xml 1
<?xml version="1.0" encoding="UTF-8"?>
<InvoiceHeader>
<Item1>
Item description
</Item1>
<Extrensic name="taxIncluded">
<percentage>
10%
</percentage>
</Extrensic>
</InvoiceHeader>
output
<?xml version="1.0" encoding="UTF-8"?>
<InvoiceHeader>
<Item1>
Item description
</Item1>
<Extrensic name="taxIncluded">
<percentage>
20%
</percentage>
</Extrensic>
</InvoiceHeader>
input xml 2
<?xml version="1.0" encoding="UTF-8"?>
<InvoiceHeader>
<Item1>
Item description
</Item1>
</InvoiceHeader>
output
<?xml version="1.0" encoding="UTF-8"?>
<InvoiceHeader>
<Item1>
Item description
</Item1>
<Extrensic name="taxIncluded">
<percentage>
20%
</percentage>
</Extrensic>
</InvoiceHeader>
I tried creating xsl but it is not working as expected, I thought of including it here but it is a very big xsl, in the above xml example I added only a part of it.
Could some one please help me how to do it?

Answer 1

Here are two ways to do it with XSLT 2.0 ...
Method 1:
<xsl:transform
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0">
<xsl:output omit-xml-declaration="yes" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:param name="taxIncluded" select="20" />
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="InvoiceHeader[not( Extrensic[#name='taxIncluded'])]">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
<Extrensic name="taxIncluded">
<percentage>
<xsl:value-of select="$taxIncluded" />%
</percentage>
</Extrensic>
</xsl:copy>
</xsl:template>
<xsl:template match="Extrensic[#name='taxIncluded']/percentage">
<xsl:copy>
<xsl:value-of select="$taxIncluded" />%
</xsl:copy>
</xsl:template>
</xsl:transform>
Method 2:
<xsl:transform
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="2.0">
<xsl:output omit-xml-declaration="yes" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*" />
<xsl:param name="taxIncluded" select="20" />
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="InvoiceHeader">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
<xsl:variable name="Ex" as="element(Extrensic)?">
<xsl:if test="not( Extrensic[#name='taxIncluded'])">
<Extrensic name="taxIncluded" />
</xsl:if>
</xsl:variable>
<xsl:apply-templates select="$Ex" />
</xsl:copy>
</xsl:template>
<xsl:template match="Extrensic[#name='taxIncluded']">
<xsl:copy>
<xsl:apply-templates select="#*"/>
<percentage>
<xsl:value-of select="$taxIncluded" />%
</percentage>
</xsl:copy>
</xsl:template>
</xsl:transform>