code: public static Object[] extract(String xmltext) throws AesException     {
  		Object[] result = new Object[3];
  		try {
  			DocumentBuilder db = Wxs.xmls();
  			StringReader sr = new StringReader(xmltext);
  			InputSource is = new InputSource(sr);
  			Document document = db.parse(is);
  
  			Element root = document.getDocumentElement();
  			NodeList nodelist1 = root.getElementsByTagName("Encrypt");
  			NodeList nodelist2 = root.getElementsByTagName("ToUserName");
  			result[0] = 0;
  			result[1] = nodelist1.item(0).getTextContent();
  			result[2] = nodelist2.item(0).getTextContent();
  			return result;
  		} catch (Exception e) {
  			e.printStackTrace();
  			throw new AesException(AesException.ParseXmlError);
  		}
  	}
docs: 提取出xml数据包中的加密消息
  @param xmltext 待提取的xml字符串
  @return 提取出的加密消息字符串
  @throws AesException