Question

I want to use JDOM to read in an XML file, then use XPath to extract data from the JDOM Document. It creates the Document object fine, but when I use XPath to query the Document for a List of elements, I get nothing.

My XML document has a default namespace defined in the root element. The funny thing is, when I remove the default namespace, it successfully runs the XPath query and returns the elements I want. What else must I do to get my XPath query to return results?

XML:

<?xml version='1.0' encoding='UTF-8'?> <collection xmlns='http://www.foo.com'> <dvd id='A'>   <title>Lord of the Rings: The Fellowship of the Ring</title>   <length>178</length>   <actor>Ian Holm</actor>   <actor>Elijah Wood</actor>   <actor>Ian McKellen</actor> </dvd> <dvd id='B'>   <title>The Matrix</title>   <length>136</length>   <actor>Keanu Reeves</actor>   <actor>Laurence Fishburne</actor> </dvd> </collection> 

Java:

public static void main(String args[]) throws Exception {     SAXBuilder builder = new SAXBuilder();     Document d = builder.build('xpath.xml');     XPath xpath = XPath.newInstance('collection/dvd');     xpath.addNamespace(d.getRootElement().getNamespace());     System.out.println(xpath.selectNodes(d)); } 

Answer 1

XPath 1.0 doesn’t support the concept of a default namespace (XPath 2.0 does). Any unprefixed tag is always assumed to be part of the no-name namespace.

When using XPath 1.0 you need something like this:

public static void main(String args[]) throws Exception {     SAXBuilder builder = new SAXBuilder();     Document d = builder.build('xpath.xml');     XPath xpath = XPath.newInstance('x:collection/x:dvd');     xpath.addNamespace('x', d.getRootElement().getNamespaceURI());     System.out.println(xpath.selectNodes(d)); }