Question

TASK : I have an existing xml document (UTF-8) which uses xml namespaces and xml schema. I need to parse to a particular element, append content (that also needs to use xml namespace prefixes) to this element and then write out the Document again.

which is the best XML parser library that I should be using for this TASK ?

I’ve seen a previous thread (Best XML parser for Java) but was not sure if dom4j or JDOM is any good for namespaces/xmlSchema and good support for UTF-8 characters.

Some parsers that seems like a task for
JDom
Dom4J
XOM
WoodStock

Any idea which one is the best ? 🙂 I use JDK 6 and would prefer NOT to use the built-in SAX/DOM facilities to do this job because that requires me to write too much code.

Would help to have some examples of doing such a task.

Answer 1

Using JDOM, taking an InputStream and making it a Document:

InputStream inputStream = (InputStream)httpURLConnection.getContent();
DocumentBuilderFactory docbf = DocumentBuilderFactory.newInstance();
docbf.setNamespaceAware(true);
DocumentBuilder docbuilder = docbf.newDocumentBuilder();
Document document = docbuilder.parse(inputStream, baseUrl);

At that point, you have the XML in a Java object. Done. Easy.

You can either use the document object and the Java API to just walk through it, or also use XPath, which I find easier (once I learned it).

Build an XPath object, which takes a bit:

public static XPath buildXPath() {
    XPathFactory factory = XPathFactory.newInstance();
    XPath xpath = factory.newXPath();
    xpath.setNamespaceContext(new AtomNamespaceContext());
    return xpath;
}


public class AtomNamespaceContext implements NamespaceContext {

    public String getNamespaceURI(String prefix) {
        if (prefix == null)
            throw new NullPointerException("Null prefix");
        else if ("a".equals(prefix))
            return "http://www.w3.org/2005/Atom";
        else if ("app".equals(prefix))
            return "http://www.w3.org/2007/app";
        else if ("os".equals(prefix))
            return "http://a9.com/-/spec/opensearch/1.1/";
        else if ("x".equals(prefix)) 
            return "http://www.w3.org/1999/xhtml";
        else if ("xml".equals(prefix))
            return XMLConstants.XML_NS_URI;
        return XMLConstants.NULL_NS_URI;
    }

    // This method isn't necessary for XPath processing.
    public String getPrefix(String uri) {
        throw new UnsupportedOperationException();
    }

    // This method isn't necessary for XPath processing either.
    public Iterator getPrefixes(String uri) {
        throw new UnsupportedOperationException();
    }
}

Then just use it, which (thankfully) doesn’t take much time at all:

return Integer.parseInt(xpath.evaluate("/a:feed/os:totalResults/text()", document));