XPath - Selecting nodes based on attribute values

billy_bob_the_3rd · November 30th, 2004, 01:54 PM

Hi,

My problem exists when the attribute is prefixed with a namespace.

For example, consider the following node saved in a file called test.xml.

<test xmlns="http://www.testsite.ca" xmlns:abc="http://www.abc.ca/test" identifier="XYZ"></test>

Now consider the following code (using VB 6.0 and MSXML 4.0)

Code:

'*********START**************
Set XmlLoadDocument = New MSXML2.DOMDocument40
'Set namespace properties
Call XmlLoadDocument.SetProperty("SelectionNamespaces", "xmlns:testNS='http://www.testsite.ca'" )
'Load test.xml into a XML document called test
Call XmlLoadDocument.Load(test.xml) 
'Use XPath to retrieve the node
Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test[@testNS:abc = 'http://www.abc.ca/test']")
'*************END*************

The node tempNode is null (Nothing). No nodes are returned.

I have also tried executing,

Code:

Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test[@abc = 'http://www.abc.ca/test']")

and

Code:

Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test[@* = 'http://www.abc.ca/test']")

none of which return any nodes.

However, if I execute

Code:

Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test[@identifier = 'XYZ']")

then I get the proper results. A node is returned.

This leads me to believe that the problem exists when attributes are prefixed with a namespace.

Anyone know how to get past this problem????

jkmyoung · November 30th, 2004, 08:31 PM

The problem is that anything prefixed "xmlns:" is seen as a namespace declaration, not an actual attribute to be processed.

From www.w3c.org http://www.w3.org/TR/1999/REC-xslt-1...#built-in-rule
"The built-in template rule for namespace nodes is also to do nothing. There is no pattern that can match a namespace node; so, the built-in template rule is the only template rule that is applied for namespace nodes."
So you really can't reference the namespace declaration at all.

joefawcett · December 1st, 2004, 07:30 AM

xmlns:abc="http://www.abc.ca/test" is a namespace declaration, it doesn't affect the test element at all in your example. To select the test element you need, after setting the Selectionnamespaces as you have done:

Code:

Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test")

There are no prefixed attributes in your example, if "identifier" were prefixed, i.e.

Code:

<test xmlns="http://www.testsite.ca" abc:identifier="XYZ" xmlns:abc="http://www.abc.ca/test"></test>

then you could do:

Code:

Set tempNode = XmlLoadDocument.selectSingleNode("testNS:test[abc:identifier = 'xyz']")

In that case you would have to declare two namespace associations:

Code:

Call XmlLoadDocument.SetProperty("SelectionNamespaces", "xmlns:testNS='http://www.testsite.ca' xmlns:abc='http://www.abc.ca/test'" )

--

Joe (Microsoft MVP - XML)

billy_bob_the_3rd · December 1st, 2004, 05:54 PM

What I really want to do is check if a namespace exists in the <test> tag. That is,

Given the xml:

Code:

<test xmlns="http://www.testsite.ca" xmlns:abc="http://www.abc.ca/test" identifier="XYZ"></test>

if namespace "http://www.abc.ca/test" exists then do something.

mhkay · December 1st, 2004, 06:12 PM

Use the namespace axis.

xsl:if test="namespace::*[. = 'http://www.abc.ca/test']"

Michael Kay
http://www.saxonica.com/