code: public static String getElementValue(Element parent, String tagName) {
  		Element element = getChildElement(parent, tagName);
  		if (element != null) {
  			NodeList nodes = element.getChildNodes();
  			if (nodes != null && nodes.getLength() > 0) {
  				for (int i = 0; i < nodes.getLength(); i++) {
  					Node node = nodes.item(i);
  					if (node instanceof Text) {
  						return ((Text) node).getData();
  					}
  				}
  			}
  		}
  
  		return null;
  	}
docs: Gets the value of the child element by tag name under the given parent
  element. If there is more than one child element, return the value of the
  first one.
  
  @param parent the parent element
  @param tagName the tag name of the child element
  @return value of the first child element, NULL if tag not exists