replace namespace prefix and add attributes using XSLT - xslt

Question

suppose I have following XML as source:
<ns0:msg xmlns:ns0="namespace0">
<ns0:hdr a_lot_of_attrs="value">
some nodes...
</ns0:hdr>
<ns0:body>
<ns0:data a_lot_of_attrs="value">
<ns1:purchase_order xmlns:ns1="namespace1">some nodes...</ns1:purchase_order>
</ns0:data>
</ns0:body>
</ns0:msg>
And I need following XML as the result:
<a:msg xmlns:a="namespace0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<a:hdr a_lot_of_attrs="value">
some nodes...
</a:hdr>
<a:body>
<a:data a_lot_of_attrs="value">
<b:purchase_order
xsi:schemaLocation="filelocation"
xmlns:b="namespace1"
xmlns:c="namespace2">some nodes...</b:purchase_order>
</a:data>
</a:body>
</a:msg>
Basically I need just to replace the namespace prefix ns0 into a and ns1 into b. Further more, the root element <a:msg> as well as the <b:purchase_order> need to be added by some additional attributes.
My attemp is by using following XSLT:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ns0="namespace0"
xmlns:ns1="namespace1"
xmlns:a="namespace0"
xmlns:b="namespace1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
exclude-result-prefixes="ns0 ns1">
<xsl:output method="xml" encoding="UTF-8" indent="yes"/>
<xsl:template match="/">
<a:msg xmlns:msg="namespace1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<xsl:copy>
<xsl:apply-templates select="ns0:msg/*"/>
</xsl:copy>
</a:msg>
</xsl:template>
<xsl:template match="/ns0:msg/ns0:body/ns0:data/ns1:purchase_order">
<b:purchase_order xsi:schemaLocation="filelocation" xmlns:c="namespace2">
<xsl:copy>
<xsl:apply-templates select="node()"/>
</xsl:copy>
</b:purchase_order>
</xsl:template>
<xsl:template match="ns0:*">
<xsl:element name="a:{local-name()}">
<xsl:apply-templates select="#* | node()"/>
</xsl:element>
</xsl:template>
<xsl:template match="ns1:*">
<xsl:element name="b:{local-name()}">
<xsl:apply-templates select="#* | node()"/>
</xsl:element>
</xsl:template>
<xsl:template match="#*">
<xsl:copy-of select="."/>
</xsl:template>
</xsl:stylesheet>
It works fine so far, except the node <purchase_order> has been populated 2 times:
<a:msg xmlns:a="namespace0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<a:hdr a_lot_of_attrs="value">
some nodes...
</a:hdr>
<a:body>
<a:data a_lot_of_attrs="value">
<b:purchase_order xmlns:b="namespace1" xmlns:c="namespace2" xsi:schemaLocation="filelocation">
<ns1:purchase_order xmlns:ns0="namespace0" xmlns:ns1="namespace1">some nodes...</ns1:purchase_order>
</b:purchase_order>
</a:data>
</a:body>
</a:msg>
I tried several times by tweaking the second <xsl:template> but could not get it right. Would someone pls advise where I get wrong here and how can I get this done?
Thanks a lot.

Answer 1

You current template that matches ns1:purchase_order contains an xsl:copy as well as the creation of the new b:purchase_order. Therefore you are copying the old node as well as creating a new one.
You can remove the xsl:copy from the template, like so:
<xsl:template match="ns1:purchase_order">
<b:purchase_order xsi:schemaLocation="filelocation" xmlns:c="namespace2">
<xsl:apply-templates select="node()"/>
</b:purchase_order>
</xsl:template>
Note that you don't necessarily have to specify the full path in the template match. You would only really need to do this if you had a second ns1:purchase_order in the XML, at a different location, that you didn't want to match.