How to use xslt to alter xml namespaces - xslt

Question

I'm trying to use xslt to change namespaces an xml file. I was hoping to get something a bit closer than I have so far but I'm going around in circles so I thought I'd ask the question a little earlier than I ordinarily would...
My XML file is
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<ns2:apple xmlns:ns2="http://veg.com/app/api/apple" xmlns:ns1="http://veg.com/app/api" xmlns:ns3="http://veg.com/app/api/apple/red"
xmlns:ns4="http://veg.com/app/banana" xmlns:ns5="http://veg.com/app/api/pear" xmlns:ns6="http://veg.com/app/api/orange"
ns1:created="2016-05-23T16:47:55+01:00" ns1:href="http://falseserver:8080/app/api/apple/1" ns1:id="1">
<ns2:name>granny smith</ns2:name>
<ns2:flavour>sweet</ns2:flavour>
<ns2:origin>southwest region</ns2:origin>
</ns2:apple>
The only part I want to change are the urls in the namespace atributes of the root element to (veg to fruit)
<ns2:apple xmlns:ns2="http://fruit.com/app/api/apple" xmlns:ns1="http://fruit.com/app/api" xmlns:ns3="http://fruit.com/app/api/apple/red"
xmlns:ns4="http://fruit.com/app/banana" xmlns:ns5="http://fruit.com/app/api/pear" xmlns:ns6="http://fruit.com/app/api/orange"
ns1:created="2016-05-23T16:47:55+01:00" ns1:href="http://falseserver:8080/app/api/apple/1" ns1:id="1">
I've tried a few things but have failed spectacularly so far. My last attempt was
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="*">
<xsl:element name="{local-name()}" namespace="http://fruit.com/app/api/apple">
<xsl:apply-templates select="#*|node()"/>
</xsl:element>
</xsl:template>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
which has given me a ridiculous result -
<?xml version="1.0" encoding="UTF-8"?><ns0:apple xmlns:ns0="http://fruit.com/app/api/apple" ns1:created="2016-05-23T16:47:55+01:00" ns1:href="http://falseserver:8080/app/api/apple/1" ns1:id="1">
<ns1:name xmlns:ns1="http://fruit.com/app/api/apple">granny smith</ns1:name>
<ns2:flavour xmlns:ns2="http://fruit.com/app/api/apple">sweet</ns2:flavour>
<ns3:origin xmlns:ns3="http://fruit.com/app/api/apple">southwest region</ns3:origin>
</ns0:apple>
I think my first and biggest issue is trying to do the correct match. As you can see I have resorted to a * but this is out of desperation rather than because I think it's the right way to go! I'm also not sure why it drops all the other namespace attributes from the tag bu this also seems to happen quite consistently in all the ways I've tried so far. I've no idea how I've managed to get the new 'tag namespaces' in the document but I suspect if I could at least get the start of the xsl doc correct I'd be much closer to the answer...

Answer 1

In the code provided (your "spectacular failure") you have left the XSLT processor to think up new prefixes. When you don't specify a prefix in xsl:element, an XSLT 1.0 processor is expected to dream one up. This changes in XSLT 2.0, which is required to put the element in the default namespace. If you want to use the prefix ns2, then specify
<xsl:element name="ns2:{local-name()}" namespace="http://fruit.com/app/api/apple">
which will work in either release (except that in XSLT 1.0, processors have blanket permission to change namespace prefixes any way they want: but most processors don't do this in ordinary circumstances).
This will work for the namespaces that are actually used in element names. It will drop namespaces that are unused. Your example appears to retain some unused namespaces from the source document, but changing the prefix.
If you know that the root element of your document is always ns2:apple, then generate that element in the output using a literal result element with all the desired namespaces.
If you don't know the name of the root element in advance, then controlling its namespace declarations is quite hard to achieve in XSLT 1.0 (and rarely needed!). In XSLT 2.0 you can do it using the xsl:namespace instruction.