Re: Weird behavior of XPath.evaluate()

[Christine Li]

Hi, Jason

Set namespace aware to true on DocumentBuilderFactory.

DocumentBuilderFactory fct = DocumentBuilderFactory.newInstance ();
fct.setNamespaceAware(true);

Christine Li
XSLT Development
IBM Toronto Lab
Tel: (905)413-2601
Email: [EMAIL PROTECTED]



"Jason Morris" <[EMAIL PROTECTED]> 
Sent by: [EMAIL PROTECTED]
10/05/2007 12:19 PM

To
xalan-j-users@xml.apache.org
cc

Subject
Weird behavior of XPath.evaluate()






Hi all,

Apologies if this has been asked before but it is driving me mad. I am 
happily able to evaluate non-namespaced XPath expressions using either an 
InputSource or a document context element. I can evaluate namespaced 
expressions using the InputSource, but it doesn't work if I evaluate a 
namespaced expression passing an Element as a context node. 

Take the example file from 
http://xml.apache.org/xalan-j/xpath_apis.html#namespacecontext 

<?xml version='1.0'?>

 <foo:document xmlns:foo="http://apache.org/foo"; xmlns:bar=" 
http://apache.org/bar";>
    <bar:element>MyBar</bar:element> 
  </foo:document>
 
I want to evaluate "/foo:document/bar:element", which should return 
"MyBar". I use the following code:

package test;

import java.util.Iterator;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathFactory ;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.xml.sax.InputSource;

public class NamespaceTest
{
    public static void main(String[] argv) throws Exception
    {
        String doc = " namespace.xml";
        String xPath = "/foo:document/bar:element";

        // Parse the doc independently to get the root Element
        DocumentBuilderFactory fct = DocumentBuilderFactory.newInstance 
();
        DocumentBuilder builder = fct.newDocumentBuilder();
        Document document = builder.parse("file:" + doc);
        Element rootElement = document.getDocumentElement();

        // Setup the namespace context 
        XPathFactory factory = XPathFactory.newInstance();
        XPath xp = factory.newXPath();
        NamespaceContext ctx = new MyNamespaceContext();
        xp.setNamespaceContext(ctx);
 
        // Create an InputSource of the file 
        InputSource is = new InputSource(doc);
 
        // This works
        String resultString1 = xp.evaluate(xPath,is);
        // This doesn't
        String resultString2 = xp.evaluate (xPath,rootElement);

        System.out.println("RES1=" + resultString1);
        System.out.println("RES2=" + resultString2);
    }
}



class MyNamespaceContext implements NamespaceContext 
{
    public String getNamespaceURI(String prefix)
    {
        if (prefix.equals("foo"))
            return " http://apache.org/foo";;
        else if ( prefix.equals("bar"))
            return "http://apache.org/bar";;
        else
            return XMLConstants.NULL_NS_URI;
    }
 
    public String getPrefix(String namespace) 
    {
        if (namespace.equals("http://apache.org/foo";))
            return "foo"; 
        else if (namespace.equals(" http://apache.org/bar";))
            return "bar";
        else
            return null;
    }

    public Iterator getPrefixes(String namespace)
    {
        return null;
    } 
} 


When I execute this (against Xalan 2.7.0), resultString1 returns "MyBar" 
correctly, resultString2 is set as empty string. Surely they should both 
return the correct result? Interestingly, if I use the exact same code to 
evaluate a namespace-free expression, both versions work fine. 

Is this a bug, or am I doing something stupid with the rootElement I am 
passing in?

Any and all assistance greatly appreciated,

Jason