How to transform Java Document object into XML String ?

When working with org.w3c.dom.Document object in java, it is often usefull to get the XML String representation for debug.
A common way to do achieve that goal is simply to use getDocumentElement() method like this:

    // Print XML Document to the output console
    org.w3c.dom.Document doc = ...
    System.out.println(doc.getDocumentElement());

However, in some case, according to the XML processor loaded, this method doesn't work. I was faced to this problem with Tomcat servlet container. In such case the following solution can help a lot especially for debug.
A way to bypass the problem is to perform a "null" XSLT transformation as shown below:

   	public static String getXMLDocString(Document arg, ServletContext context)
	{
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		
		String 	xslFilePath = context.getRealPath("default.xsl");
		File	xslFile		= new File(xslFilePath);
		
		try {
			TransformerFactory tFactory = TransformerFactory.newInstance();
			Transformer transformer =
				tFactory.newTransformer(
					new StreamSource(xslFile) );
			transformer.transform(new DOMSource(arg), new StreamResult(baos));
		} catch (TransformerConfigurationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (TransformerFactoryConfigurationError e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (TransformerException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
		
		String res = new String(baos.toByteArray());

		return res;

	}

Note the use of default.xsl stylesheet, which tranform a XML file into the same XML file: