public List<Role> listRoles(String userName,  PrincipalType principalType)
      throws HiveException {
    try {
      return getMSC().list_roles(userName, principalType);
    } catch (Exception e) {
      throw new HiveException(e);
    }
  }
Get all existing role names.

@return List of role names.
@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java