code: public void registerAttribute(String namespacePrefix, String attributeName, Class<?> clazz, String fieldName, Class<?> fieldClass) {
          if (!_namespaces.containsKey(namespacePrefix))
              throw new RuntimeException("Namespace prefix '" + namespacePrefix + "' has not been registered yet");
          _xstream.aliasAttribute(clazz, fieldName, namespacePrefix + ":" + attributeName);
          _xstream.useAttributeFor(fieldName, fieldClass);
      }
docs: Registers an attribute corresponding to a specific field of a specific class, in a given namespace.
  @param namespacePrefix namespace prefix, required
  @param attributeName attribute name, required
  @param clazz class containing the field, required
  @param fieldName field name, required
  @param fieldClass field type, required