Document to String y viceversa

	public static String documentToString(Document doc) {
		return sourceToString(new DOMSource(doc));
	}
	
	public static String sourceToString(Source source) {
		try {
			StringWriter sw = new StringWriter();
			TransformerFactory tf = TransformerFactory.newInstance();
			Transformer transformer = tf.newTransformer();
			transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
			transformer.setOutputProperty(OutputKeys.METHOD, "xml");
			transformer.setOutputProperty(OutputKeys.INDENT, "yes");
			transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");

			transformer.transform(source, new StreamResult(sw));
			return sw.toString();
		} catch (Exception ex) {
			throw new RuntimeException("Error converting to String", ex);
		}
	}
	
	public static Source toSource(String xml){
		return new StreamSource(new StringReader(xml));
	}
	
	public static Document stringToDocument(String xml) {
		Document doc = null;
		try {
			DocumentBuilder db = DocumentBuilderFactory.newInstance().newDocumentBuilder();
			doc = db.parse( new InputSource( new StringReader( xml ) ) ); 
		} catch (Exception e) {
			throw new RuntimeException("Error converting to String", e);
		}
		return doc;
	}
	
	public static Source stringToDocumentToSource(String xml) {
		return new DOMSource(stringToDocument(xml));
	}
	
	public static Source stringToSource(String xml) {
		return new StreamSource(new StringReader(xml));
	}

¿Porque es importante el Source?. A la hora de realizar el marshall/unmarshall de objetos y strings JAXB siempre quiere datos de tipo Source.

	public Object xmlToObject(String xml) throws Exception {
		ByteArrayInputStream bais = new ByteArrayInputStream(xml.getBytes(getEncoding()));
		StreamSource source = new StreamSource(bais);
		return xmlToObject(source);
	}
	
	public Object xmlToObject(Source source) throws Exception {
		return jaxb2Marshaller.unmarshal(source);
	}