xslt1.0 / xml-为什么在添加名称空间信息时xsl文件将停止呈现xml

Question

I've got an xsl file that has been working fine. The templates are all in place and everything shows on the page when the root node is the following:

<Document>
  <...>
</Document>

However, if namespace information is added to the xml document like so:

<Document  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi_schemaLocation="urn:hl7-org:v3 CDA_SDTC.xsd" xmlns="urn:hl7-org:v3" xmlns:cda="urn:hl7-org:v3" xmlns:sdtc="urn:hl7-org:sdtc">
  <...>
</Document>

My stylesheet hasn't changed and it was working for the first example:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:ms="urn:schemas-microsoft-com:xslt"
  xmlns="http://www.w3.org/1999/xhtml">

  <xsl:template match="/">
  </xsl:template>
</xsl:stylesheet>

There's nothing being read from the xml document at all on the web output. What would be the cause for that?

I made the following change to the XSLT file:

<xsl:stylesheet
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ms="urn:schemas-microsoft-com:xslt"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:hl7-org:v3 CDA_SDTC.xsd" 
xmlns="urn:hl7-org:v3" 
xmlns:cda="urn:hl7-org:v3" 
xmlns:sdtc="urn:hl7-org:sdtc"
>

but that throws an error on the xsi:schemaLocation because of the space between v3 and CDA. If I take out that one line like so:

<xsl:stylesheet
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ms="urn:schemas-microsoft-com:xslt"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="urn:hl7-org:v3" 
xmlns:cda="urn:hl7-org:v3" 
xmlns:sdtc="urn:hl7-org:sdtc"
>

Then I still get nothing rendered out of the xml document onto the page. I know I'm missing something but I'm not familiar enough with xsl to know what it is.

Thanks for any help.

Answer 1

In XPath 1.0 expressions, unprefixed names always refer to nodes that are not in a namespace. If you want to refer to nodes that are in a namespace then you need to bind the relevant namespace URI to a prefix in the stylesheet and use that prefix in your XPaths.

In your example the document

<Document>
  <!--...-->
</Document>

has a root element with the local name Document and no namespace, so it can be matched by an XPath expression of /Document . But the document

<Document  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi_schemaLocation="urn:hl7-org:v3 CDA_SDTC.xsd" xmlns="urn:hl7-org:v3" xmlns:cda="urn:hl7-org:v3" xmlns:sdtc="urn:hl7-org:sdtc">
  <!--...-->
</Document>

has a root element with local name Document in the urn:hl7-org:v3 namespace, which is not matched by the path /Document . In order to match that you would need to add

xmlns:hl7="urn:hl7-org:v3"

to the <xsl:stylesheet> tag, and then use XPath expressions like /hl7:Document . Since the default namespace xmlns="..." applies to descendant elements as well, you'll probably find that you have to add this prefix in many places, eg /Document/a/b would probably need to change to /hl7:Document/hl7:a/hl7:b . In XSLT 2.0 you can use xpath-default-namespace but this option is not available in 1.0.

The fact that the element name doesn't have a prefix in the original XML is irrelevant - what matters to XPath is the local name and the namespace URI.

Answer 2

Your input XML no contains a default namespace xmlns="urn:hl7-org:v3" . This means your XSLT also needs to know this namespace.

The XSLT processor matches on the namespace URI. So in your XSLT you can use a different prefix, for example putting xmlns:pref="urn:hl7-org:v3" in your XSLT.

You could than select elements in your XSLT with use of that prefix: <xsl:value-of select="/pref:rootElement/pref:childElement" />