一个简单方法：构造xml的document，并将其转换为string

    首先，构造一个document对象：

	Document doc = null;
	try {
            doc = DocumentBuilderFactory.newInstance()
				.newDocumentBuilder().newDocument();
	} catch (ParserConfigurationException e) {
        e.printStackTrace();
        return null;
	}

    然后，在doc中加入需要的节点，例如：

	Element register = doc.createElement("Register");
	register.setAttribute("id", REGISTER_ATTRIB_ID);
	register.setAttribute("type", REGISTER_ATTRIB_TYPE);
	doc.appendChild(register);
		
	Element params = doc.createElement("Params");
	register.appendChild(params);

        Element item = doc.createElement(tagName);
        item.appendChild(doc.createTextNode(textNode));
        params.appendChild(item);

    最后，将document对象转换成字符串：

	public static String convertDocToString(Document doc, String propertyName, String progertyValue){
		Transformer transformer = null;
		try {
			transformer = TransformerFactory.newInstance().newTransformer();
		} catch (TransformerConfigurationException e) {
			e.printStackTrace();
			return null;
		} catch (TransformerFactoryConfigurationError e) {
			e.printStackTrace();
			return null;
		}
		transformer.setOutputProperty(propertyName, progertyValue);
		DOMSource domSource = new DOMSource(doc);
		StreamResult streamResult = new StreamResult();
		
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		streamResult.setOutputStream(os);
		try {
			transformer.transform(domSource, streamResult);
		} catch (TransformerException e) {
			e.printStackTrace();
			return null;
		} finally {
			try {
				os.flush();
				os.close();
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}
		
		return os.toString();
	}