Question

When running this code in Eclipse I get only null values:

    String recordsAsXML = "<vGVC:Row xmlns:vGVC=\"urn:com.versai:Bacon:GetViewContentsResponse.v1.0\"><vGVC:Column><vGVC:Value>aaa0</vGVC:Value><vGVC:ObjectName>2ff31656-b10c-11e0-99f6-e01321378d2a</vGVC:ObjectName></vGVC:Column><vGVC:ModifiedAfterQuery>false</vGVC:ModifiedAfterQuery></vGVC:Row>";


    DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
    domFactory.setNamespaceAware(true);
    DocumentBuilder builder = domFactory.newDocumentBuilder();
    InputSource is = new InputSource();
    is.setCharacterStream(new StringReader(recordsAsXML));

    Document doc = builder.parse(is);

    XPathFactory factory = XPathFactory.newInstance();
    XPath xpath = factory.newXPath();
    XPathExpression expr = xpath.compile("//vGVC:Value/text()");

    Object result = expr.evaluate(doc, XPathConstants.NODESET);
    NodeList nodes = (NodeList) result;

    for (int i = 0; i < nodes.getLength(); i++) {
        System.out.println(nodes.item(i).getNodeValue()); 
    }

I’m trying to extract the “aaa0” value.
Could you please help me understand what I’m doing wrong?

Thanks in advance, Michal.

Answer 1

You should use namespace context to let XPath know about your namespace, for example like this:

xpath.setNamespaceContext(new NamespaceContext() {  
    @Override public Iterator<?> getPrefixes(String namespaceURI) { return null; }
    @Override public String getPrefix(String namespaceURI) { return "vGVC"; }
    @Override public String getNamespaceURI(String prefix) { return "urn:com.versai:Bacon:GetViewContentsResponse.v1.0"; }
});

This should be done before calling evaluate, and if you have more than one namespace to handle, you can add them all in one implementation and use if statements to return the right prefix/URI.

More details in the javadocs here: http://download.oracle.com/javase/6/docs/api/javax/xml/namespace/NamespaceContext.html