code: public static String getEventHandler(String className) throws IOException {
          if (getEventHandlers() != null) {
              String newHandler = getEventHandlers().get(className);
              if (newHandler != null)
                  return newHandler;
          }
          return className;
      }
docs: If the className argument needs to be mapped to a new event handler class,
  returns the new class name; otherwise returns the unmodified argument.