static String getUsernameFromConf(Configuration conf) {
    String oldStyleUgi = conf.get(DEPRECATED_UGI_KEY);
    if (oldStyleUgi != null) {
      // We can't use the normal configuration deprecation mechanism here
      // since we need to split out the username from the configured UGI.
      LOG.warn(
        DEPRECATED_UGI_KEY + " should not be used. Instead, use " + HBASE_HTTP_STATIC_USER + ".");
      return Iterables.get(Splitter.on(',').split(oldStyleUgi), 0);
    } else {
      return conf.get(HBASE_HTTP_STATIC_USER, DEFAULT_HBASE_HTTP_STATIC_USER);
    }
  }
Retrieve the static username from the configuration.
hbase-http/src/main/java/org/apache/hadoop/hbase/http/lib/StaticUserWebFilter.java