toString-format XML documents for comparison purposes etc.

xml formatting

public final class XmlUtil
{
    public static String formatXml(Document document)
        throws Exception
    {
        // the DocumentBuilderFactory can't reliably be configured to produce
        // identical output from semantically identical documents, contrary to what
        // its methods would suggest. Hence:
        DOMImplementationRegistry registry = DOMImplementationRegistry.newInstance();
        DOMImplementationLS impl = (DOMImplementationLS)registry.getDOMImplementation("LS");
        
        LSSerializer writer = impl.createLSSerializer();
        writer.getDomConfig().setParameter("format-pretty-print", Boolean.TRUE);
        
        LSOutput output = impl.createLSOutput();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        output.setByteStream(baos);
        writer.write(document, output);
        
        return baos.toString("UTF-8");
    }
}