Evaluating xpath expressions

Question

Hi all,
I have an xml document as
<?xml version="1.0" encoding="UTF-8"?>
<purchaseReport xmlns="http://www.example.com/Report" >
<regions>
<zip code="95819">
<part number="872-AA" quantity="1"/>
<part number="926-AA" quantity="1"/>
<part number="833-AA" quantity="1"/>
<part number="455-BX" quantity="1"/>
</zip>
<zip code="63143">
<part number="455-BX" quantity="4"/>
</zip>
</regions>
<parts>
<part number="872-AA">Lawnmower</part>
</parts>
</purchaseReport>
when I evaluate the for an expression xpath_object.evaluate(f,"/purchaseReport/parts/part/@number",NODE)
I am getting null as return value.
I have set the namespace context for xpath_object as
xpath_object.setNameSpaceContext(new name_space_context());
class name_space_context implements NamespaceContext{
public String getNamespaceURI(String prefix){
//System.out.println("A call was made here");
if(prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)){
System.out.println("A call was made here");
return "http://www.example.com/Report";
else if(prefix.equals(XMLConstants.XML_NS_PREFIX)) {
System.out.println("A call was made here");
return XMLConstants.XML_NS_URI;
else if (prefix.equals(XMLConstants.XMLNS_ATTRIBUTE)){
System.out.println("A call was made here");
return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
else if(prefix.equals("def")){
System.out.println("A call was made here def");
return "http://www.example.com/Report";
else if(prefix.equals("si")){
System.out.println("A call was made here si");
return "http://www.example.com/Report/si";
else if(prefix.equals("")){
System.out.println("A call was made here empty");
return "http://www.example.com/Report";
else {
return "There is no matching prefix with the given input" + prefix;
please explain why me I am getting null when I evalute the expression.

Answer 1

Hi tsuji,
I am trying to update the element value in my xml , by getting input the xml and the xpath.
My code is as below.
InputSource is;
is = new InputSource(new StringReader(input.toString()));
Node node = (Node)xPath.evaluate(XPATH, is, XPathConstants.NODE);
node.setTextContent(newValue);
I succeeded in evaluating the namespace prefix also.
After updating the value of the node, I tried to display the updated xml. But i couldnt succeed.
i tried,
Making 'Document' out of the 'is' - but failed throws NullPointerException in Document doc=dBuilder.parser(is)
Please help me in displaying the updated XMLdocument.
I have a doubt here, in this case like mere changing the value of the node, will it change the original InputSource 'is'
But , when i used
NodeIterator nl = XPathAPI.selectNodeIterator(doc, xpath); //here doc is the Document object, xpath is String object
n=nl.nextNode();
n.setTextContent(newValue);
Then when i tried displaying the doc again, it gave me the updated document.
I couldnt proceed with NodeIterator , i couldnt apply the setNamespaceContext.
Kindly help me in this regard.
Thanks,
Sabarisri. N