Re: [xml] Namespace Query Issue

["Martin (gzlist)" <gzlist googlemail com>]

On 18/04/2008, Alistair Leslie-Hughes <leslie_alistair hotmail com> wrote:
> Hi,
>
>  When use xmlXPathEval with the query "/root/WEB:Site" on the following xml
>
>  <?xml version=\"1.0\"?>
>  <root xmlns:WEB='http://www.winehq.org'>
>      <WEB:Site version=\"1.0\" />
>  </root>
>
>  I get the following error
>  XPath error : Undefined namespace prefix
>  xmlXPathEval: evaluation failed
>
>  Using the same xml and query in MSXML it works.
>
>  Can someone explain what I am doing wrong?
>
>  Best Regards
>   Alistair Leslie-Hughes

You need to register the namespace prefix/uri pair on the xpath context.

See:
http://xmlsoft.org/html/libxml-xpathInternals.html#xmlXPathRegisterNs

Some example xpath code:
http://xmlsoft.org/examples/xpath1.c

Or python version, which is brief enough for email:
>>> import libxml2
>>> doc = libxml2.parseDoc("""<?xml version="1.0"?>
... <root xmlns:WEB='http://www.winehq.org'>
...      <WEB:Site version="1.0"/>
... </root>""")
>>> ctx = doc.xpathNewContext()
>>> ctx.xpathRegisterNs("WEB", "http://www.winehq.org";)
0
>>> ctx.xpathEval("count(//WEB:*)")
1.0

This one really needs to go on an FAQ thingy really.

Martin