presto-hive/src/main/java/io/prestosql/plugin/hive/authentication/HiveIdentity.java/HiveIdentity/HiveIdentity
class HiveIdentity:    public HiveIdentity(ConnectorIdentity identity)
    {
        requireNonNull(identity, "identity is null");
        this.username = Optional.of(requireNonNull(identity.getUser(), "identity.getUser() is null"));
    }