public static UserProvider instantiate(Configuration conf) {
    Class<? extends UserProvider> clazz =
      conf.getClass(USER_PROVIDER_CONF_KEY, UserProvider.class, UserProvider.class);
    return ReflectionUtils.newInstance(clazz, conf);
  }
Instantiate the {@link UserProvider} specified in the configuration and set the passed
configuration via {@link UserProvider#setConf(Configuration)}
@param conf to read and set on the created {@link UserProvider}
@return a {@link UserProvider} ready for use.
hbase-common/src/main/java/org/apache/hadoop/hbase/security/UserProvider.java