Parse namespaced xml with ruby nokogiri - ruby

Question

I have as second of xml
<Environment
Name="test"
xmlns="http://schemas.dmtf.org/ovf/environment/1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:oe="http://schemas.dmtf.org/ovf/environment/1"
oe:id="123456789">
<PropertySection>
<Property oe:key="mykey" oe:value="test"/>
</PropertySection>
</Environment>
I'm using ruby and nokogiri to parse the document. i.e.
file = File.open('/tmp/myxml.xml')
doc = Nokogiri::XML(file)
env = doc.at('Environment')
id = env['id']
printf("ID [%s]\n", id)
properties = env.at('PropertySection')
This works and successfully prints the id from the xml.
I now want to access the Property attribute with the key 'mykey'. I tried the following:
value = properties.at('Property[#key="mykey"]')['value']
printf("Value %s\n", value)
Unfortunately the properties.at method returns a nil object. I tried modifying the xml itself to remove the 'oe' namespace from the attribute 'key'. Re-running my script it works.
How can I get nokogiri to recognise the namespace when calling .at() ?

Answer 1

You should use the Nokogiri namespace syntax: http://nokogiri.org/tutorials/searching_a_xml_html_document.html#namespaces.
First, make sure you have namespaces you can use:
ns = {
'xmlns' => 'http://schemas.dmtf.org/ovf/environment/1',
'oe' => 'http://schemas.dmtf.org/ovf/environment/1'
}
(I'm defining both even though they are the same in this example). You might also look into using the namespaces already available in doc.collect_namespaces.
Then you can just do:
value = properties.at('./xmlns:Property[#oe:key="mykey"]/#oe:value', ns).content
Note that I am using ./ here because, for this specific search, Nokogiri interprets the XPath as CSS without it. You may wish to use .//.