Weird behavior of XPath.evaluate()

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Weird behavior of XPath.evaluate()

Weird behavior of XPath.evaluate()

2007-05-10 - By Jason Morris

Reply: 1 2 3 4

Perfect - works like a charm. Thanks so much Christine and Keshlam for a
simple fix to a stupid mistake!

Jason

On 5/10/07, Christine Li <jycli@(protected)> wrote:
>
>
> 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
> * <http://xml.apache.org/xalan-j/xpath_apis.html#namespacecontext>
>
> <?xml version='1.0'?>
>
> <foo:document xmlns:foo="*http://apache.org/foo* <http://apache.org/foo>"
> xmlns:bar="* http://apache.org/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* <http://apache.org/foo>";
> else if ( prefix.equals("bar"))
> return "*http://apache.org/bar* <http://apache.org/bar>";
> else
> return XMLConstants.NULL_NS_URI;
> }
>
> public String getPrefix(String namespace)
> {
> if (namespace.equals("*http://apache.org/foo*<http://apache.org/foo>
> "))
> return "foo";
> else if (namespace.equals("* http://apache.org/bar*<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
>
>

Perfect - works like a charm. Thanks so much Christine and Keshlam for a simple
fix to a stupid mistake! Jason <div>On
5/10/07, Christine Li <<a href="mailto:jycli
@(protected)">
jycli@(protected)</a>> wrote:<blockquote class="gmail_quote" style=
"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding
-left: 1ex;">
 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: <a href="mailto:jycli@(protected)" target="_blank" onclick="return top.js
.OpenExtLink(window,event,this)">jycli@(protected)</a>
 
 
 
<table width="100%">
<tbody><tr valign="top">
<td width="40%">"Jason Morris"
<<a href="mailto:jason.morris@(protected)" target="_blank" onclick="return
top.js.OpenExtLink(window,event,this)">jason.morris@(protected)</a>> 
 Sent by: <a href="mailto:jm56692@(protected)
" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">jm56692
@(protected)</a>
10/05/2007 12:19 PM
</td><td width="59%">
<table width="100%">
<tbody><tr valign="top">
<td>
<div align="right">To</div>
</td><td><a href="mailto:xalan-j-users@(protected)
.apache.org" target="_blank" onclick="return top.js.OpenExtLink(window,event
,this)">xalan-j-users@(protected)</a>
</td></tr><tr valign="top">
<td>
<div align="right">cc</div>
</td><td>
 </td></tr><tr valign="top">
<td>
<div align="right">Subject</div>
</td><td>Weird behavior of XPath.evaluate()</td></tr></tbody></table>
 
<table>
<tbody><tr valign="top">
<td>
 </td><td> </td></tr></tbody></table>
 </td></tr></tbody></table><div>
 
 
 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" onclick="return top.js.OpenExtLink
(window,event,this)">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" onclick="return top.js.OpenExtLink(window,event,this)">http://apache.org/foo</a>
"
xmlns:bar="<a href="http://apache.org/bar" target="_blank" onclick=
"return top.js.OpenExtLink(window,event,this)">
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" onclick="return top.js.OpenExtLink(window,event
,this)">
http://apache.org/foo</a>"; 
       else if ( prefix.equals("bar")) 
           return "<a href="http:/
/apache.org/bar" target="_blank" onclick="return top.js.OpenExtLink(window,event
,this)">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" onclick="return top.js.OpenExtLink(window,event
,this)">http://apache.org/foo</a>
")) 
           return "foo"; 
       else if (namespace.equals("<a href=
"http://apache.org/bar" target="_blank" onclick="return top.js.OpenExtLink
(window,event,this)">
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 

 </div></blockquote></div>