Regarding xpath parsing of xml with default namespace using Saxon

Question

I wanted some info related to xpath parsing of default namespace using saxon. I am using the Saxon-HE-9.5.1-3.jar to use xpath 2 features in my code. After including the saxon library in the class path, I am facing a issue parsing xpath for XML documents with default namespaces.

Sample XML in am using :

<?xml version="1.0" encoding="utf-8"?>
<RESPONSE  xmlns="http://www.abc.com/" responseCode="200">
  <HEADER>
    <HITS>100</HITS>
  </HEADER>
</RESPONSE>

Valid XPATH: /RESPONSE/HEADER/HITS

Below are the cases where it works and does not work:

1. "XPATH Works" : When no namespace is specified
   Example : <RESPONSE responseCode="200">

2. "XPATH Works" : When namespace with prefix is given
   Example : <RESPONSE xmlns:res="http://www.abc.com/" responseCode="200">

3. "XPATH does not work" : When default namespace with out prefix is given Example : <RESPONSE xmlns="http://www.abc.com/" responseCode="200">

Can you please help me out on why saxon treats no namespace and default namespace in a different way ? Also how do I solve the case of doing xpath for documents with default namespace.

Below is chunks of my code:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import net.sf.saxon.xpath.XPathEvaluator;
import net.sf.saxon.xpath.XPathFactoryImpl;

.
.
.

DocumentBuilder builder;
Document doc;

DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
builder = domFactory.newDocumentBuilder();
doc = builder.parse(new ByteArrayInputStream(b, 0, size));

XPathFactory factory = XPathFactoryImpl.newInstance(XPathConstants.DOM_OBJECT_MODEL);
XPathEvaluator xpathCompiler = (XPathEvaluator) factory.newXPath();
XPathExpression expr = xpathCompiler.compile(xpath);
NodeList childNodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);

Thanks & Regards Pratap

Answer 1

This is not Saxon-specific but rather a fundamental part of how namespaces work. In your examples 1 and 2 the RESPONSE element is not in a namespace but in case 3 it (and all its descendants) are in the http://www.abc.com/ namespace. With the javax.xml.xpath API you need to define a NamespaceContext if you want to be able to match nodes in a specific namespace, or since you're in XPath 2.0 you can use the *:localName notation to match all nodes with a given local name regardless of their namespace.

/*:RESPONSE/*:HEADER/*:HITS