// CS639: Show how to use XPath when the XML has a namespace.

// See the catalog.xml file in this directory (using default NS)

// and the catalog1.xml file that is edited to use a prefix e:

// This program is available from http://www.edankert.com/defaultnamespaces.html

// in the linked xpath-examples.zip

// We need to provide the XPath processor with a way to look up prefixes

// we use in the XPath expression. Here we just set up one prefix "edx"

// to be used for the NS in the XML file, and then use it in the XPath

// expression //edx:cd to find all the cd elements in the XML file,

// (whatever their prefix is in the XML file.)

import …

public class XPathExample {

public static void main(String[] args) {

try {

DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();

domFactory.setNamespaceAware(true);

DocumentBuilder builder = domFactory.newDocumentBuilder();

Document document = builder.parse(new InputSource("file:catalog1.xml"));

XPathFactory factory = XPathFactory.newInstance();

XPath xpath = factory.newXPath();

xpath.setNamespaceContext(new NamespaceContext() {

public String getNamespaceURI(String prefix) {

if (prefix.equals("edx")) {

return "http://www.edankert.com/examples/";

}

return "";

}

public String getPrefix(String namespaceURI) {

if (namespaceURI.equals("http://www.edankert.com/examples/")) {

return "edx";

}

return "";

}

public Iterator<String> getPrefixes(String namespaceURI) {

List<String> list = new ArrayList<String>();

if (namespaceURI.equals("http://www.edankert.com/examples/")) {

list.add("edx");

}

return list.iterator();

}

});

Object nodes = xpath.evaluate("//edx:cd", document.getDocumentElement(), XPathConstants.NODESET);

if (nodes instanceof NodeList) {

for (int i = 0; i < ((NodeList)nodes).getLength(); i++) {

System.out.println(((NodeList)nodes).item( i).getTextContent());

}

}

} catch (ParserConfigurationException e) {

e.printStackTrace();

} catch (XPathExpressionException e) {

e.printStackTrace();

} catch (SAXException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

}

File catalog1.xml

<?xml version="1.0"?>

<e:catalog xmlns:e="http://www.edankert.com/examples/">

<e:cd>

<e:artist>Stoat</e:artist>

<e:title>Future come and get me</e:title>

</e:cd>

<e:cd>

<e:artist>Sufjan Stevens</e:artist>

<e:title>Illinois</e:title>

</e:cd>

<e:cd>

<e:artist>The White Stripes</e:artist>

<e:title>Get behind me satan</e:title>

</e:cd>

</e:catalog>

java XPathExample

Stoat

Future come and get me

Sufjan Stevens

Illinois

The White Stripes

Get behind me satan