Weird behavior of XPath.evaluate()

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Weird behavior of XPath.evaluate()

Weird behavior of XPath.evaluate()

2007-05-10 - By Christine Li

Reply: 1 2 3 4

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: jycli@(protected)

"Jason Morris" <jason.morris@(protected)>
Sent by: jm56692@(protected)
10/05/2007 12:19 PM

To
xalan-j-users@(protected)
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

 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: jycli@(protected)
 
 
 
<table width=100%>
<tr valign=top>
<td width=40%>"Jason Morris"
<jason.morris@(protected)> 
 Sent by: jm56692@(protected)
10/05/2007 12:19 PM
<td width=59%>
<table width=100%>
<tr valign=top>
<td>
<div align=right>To</div>
<td>xalan-j-users@(protected)
<tr valign=top>
<td>
<div align=right>cc</div>
<td>
<tr valign=top>
<td>
<div align=right>Subject</div>
<td>Weird behavior of XPath.evaluate()<
/table>
 
<table>
<tr valign=top>
<td>
<td></table>
 </table>
 
 
 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 <a href="http://xml.apache.org/xalan-j/xpath
_apis.html#namespacecontext" target=_blank>http://xml
.apache.org/xalan-j/xpath_apis.html#namespacecontext
</a> 
 
<?xml version='1.0'?> 
 
<foo:document xmlns:foo="<a href=http://apache.org/foo target=
_blank>http://apache.org/foo</a>"
xmlns:bar="<a href=http://apache.org/bar target=_blank>
http://apache.org/bar</a>"> 
   <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&quot
;; 
 
       // 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 "<a href=http:/
/apache.org/foo target=_blank>
http://apache.org/foo</a>"; 
       else if ( prefix.equals("bar")) 
           return "<a href=http:/
/apache.org/bar target=_blank>http://apache.org/bar</a>"; 
       else 
           return XMLConstants.NULL_NS_URI; 
   } 
    
   public String getPrefix(String namespace) 
   { 
       if (namespace.equals("<a href=http:/
/apache.org/foo target=_blank>http://apache.org/foo</a>")) 
           return "foo"; 
       else if (namespace.equals("<a href=http
://apache.org/bar target=_blank>
http://apache.org/bar</a>")) 
           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