From: Aaron Patterson <aaron@...>
Date: 2009-08-03T07:25:45+09:00
Subject: Re: [libxml]: Can't find nodes using XPath, namespaces mess

On Sat, Aug 01, 2009 at 05:33:31AM +0900, Stanislaw Wozniak wrote:
> Hi,
> 
> I am having problems accessing elements in the XML documents using
> XPath. My xml document looks like that:
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <configuration-data
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
> xsi:schemaLocation="urn:company:platform:foundation:configuration:defn:v1"
> xmlns="urn:company:platform:foundation:configuration:defn:v1">

  ^^^^^ That says that all nodes inside this document (if not explicitly
  namespaced) belong to an implicit namespace

> <attributeList>
> <attribute name="siteid" validationRuleName="String" description="Site
> id">
> <tree name="siteid_hierarchy">
> <treenode name="Root">
> <treenode name="1" />
> </treenode>
> </tree>
> </attribute>
> </attributeList>
> </configuration-data>
> 
> 
> My XPath only works when I remove all the namespaces from the root node
> but I do need to access it without modifying the xml.

You need to register that namespace with the libxml xpath engine.  I'm
not sure how you register namespaces with libxml-ruby, but with
nokogiri, I would do this:

  doc = Nokogiri::XML(xml)
  doc.xpath('//ns:attribute', 'ns' => 'urn:company:platform:foundation:configuration:defn:v1')

Nokogiri will automatically register root level namespaces, so you could
also do this:

  doc = Nokogiri::XML(xml)
  doc.xpath('//xmlns:attribute')

I know there is a way to do this with libxml-ruby, I just don't know the
syntax off the top of my head.  Look through the libxml-ruby
documentation for "find", and I'm sure you'll find how to register
namespaces.

-- 
Aaron Patterson
http://tenderlovemaking.com/