@Override
  public UserGroupInformation getUser() {
    if (username == null || "".equals(username)) {
      return null;
    }
    return UserGroupInformation.createRemoteUser(username);
  }
Represents the identity information stored in an HBase authentication token.
hbase-client/src/main/java/org/apache/hadoop/hbase/security/token/AuthenticationTokenIdentifier.java