----- Original Message -----
Sent: Wednesday, September 26, 2001 8:58
AM
Subject: RE: [dom4j-user] simplest way to
use namespaces URI in xpath in dom4j?
Hi James,
You are right about the confusing aspects of namespaces, esp.
regarding XPath expressions. The standard states that namespace prefixes in
XPath expressions are resolved with regard to the "expression context", which
I presume is what part of the tree is currently under
examination.
In the following example XML document, the prefix z is mapped
to three different namespaces on three different elements:
<?xml version="1.0"?>
<z:A
xmlns:z="urn:zorglub">
<z:B
xmlns:z="urn:zappa">
<z:C
xmlns:z="urn:zoot">
</z:C>
</z:B>
</z:A>
If I do selectNodes("//z:*") on the document node I get both
z:A, z:B and z:C back. This would indicate to me that the XPath namespace
prefixes used are not "totally independant of the prefixes used in the source
document", as you state, but I guess this would depend on exactly what is
meant by the "expression context".
Of course, your suggestion should still work since it
establishes a NamespaceContext explicitly.
Any XPath gurus care to comment?
Cheers,
-- Steen
-----Original Message-----
From: James
Strachan [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, September 26, 2001 1:07 AM
To: Steen Lehmann - SilverStream; 'Martijn Koster'
Cc: [EMAIL PROTECTED]
Subject:
Re: [dom4j-user] simplest way to use namespaces URI in xpath in dom4j?
Hi Guys
One other option is to explicity setup an
org.jaxen.NamespaceContext object with one or more namespace prefixes matched
to the namespace URIs you need which can then be used in an XPath.
I'm thinking of adding something like the following to the
XPath interface (along with maybe similar changes in Jaxen)
Document doc = ..;
// create the XPath with our namespace prefixes
XPath xpath = doc.createXPath( "/foo:aaa/foo:bbb/foo:xxx"
);
// map the prefixes to the URIs we want
xpath.addNamespace( "foo", "http://www.example.org/my/" );
// now lets use it
List list =
xpath.selectNodes( doc );
A word of warning though - namespaces seem to be an area of
much confusion - but the namespace prefixes that are mapped to URIs inside an
XPath expressoin (such as the above xpath object) are totally independent of
the prefixes used in the source document. To put that another way, it doesn't
matter what prefixes you choose to use in your XPath expressions, only what
URIs they map to and the namespace URIs that are in the source
document.
James
----- Original Message -----
From: Steen Lehmann - SilverStream
To: 'Martijn Koster'
Cc:
'[EMAIL PROTECTED]'
Sent: Tuesday,
September 25, 2001 7:24 AM
Subject: RE: [dom4j-user]
simplest way to use namespaces URI in xpath in dom4j?
This is a way to match on a known namespace uri and local
element name. It's a bit on the verbose side.
/*[local-name()="aaa" and namespace-uri()="http://www.example.org/my/"]/*[local-name()="bbb"
and namespace-uri()="http://www.example.org/my/"]
If you know that no other elements are called aaa or bbb in
the document regardless of namespaces, you can omit the test for namespace-uri
in the expression and end up with:
/*[local-name()="aaa"]/*[local-name()="bbb"]
which is a bit nicer.
BTW you will want to use
single quotes instead of double quotes (or escape the double quotes) to embed
the expressions in a Java String.
-- Steen
> -----Original
Message-----
> From: Martijn Koster [mailto:[EMAIL PROTECTED]]
> Sent: Monday, September 24, 2001 6:16 PM
> To: [EMAIL PROTECTED]
> Subject: [dom4j-user] simplest way to use
namespaces URI in xpath in
> dom4j?
>
>
> What is the easiest way in Dom4J to specify an XPath expression
for a
> document where you know the namespace URI
of the desired nodes, but
> not the prefix? Ie in:
>
> <?xml
version='1.0'?>
> <my:aaa xmlns:my="http://www.example.org/my/"
>
xmlns:his="http://www.example.org/his/">
> <my:bbb>
> <my:xxx/>
> <his:xxx/>
> </my:bbb>
> </my:aaa>
>
> I want to select element my:xxx, but I don't know
the prefix "my",
> only "http://www.example.org/my/". I can
navigate to it using QNames,
> but I want to use a
single XPath expression. I can do it by hand:
>
> Namespace ns =
> root.getNamespaceForURI("http://www.example.org/my/");
> String prefix = ns.getPrefix();
> doc.selectNodes("/" + prefix ":aaa/"
+ prefix + ":bbb/" +
> prefix + ":xxx");
>
> but that gets ugly.
Is there a way I can do something like:
>
> doc.selectNodes("/aaa/bbb/xxx", ns);
>
> or
>
> doc.selectNodes(new
XPathExpression("/aaa/bbb/xxx", ns));
>
> or some such?
>
> -- Martijn
>
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