public void test_maxUsernameLength() throws IOException {
        FessProp.propMap.clear();
        FessConfig fessConfig = new FessConfig.SimpleImpl() {
            @Override
            public Integer getLdapMaxUsernameLengthAsInteger() {
                return Integer.valueOf(-1);
            }
        };
        File file = File.createTempFile("test", ".properties");
        file.deleteOnExit();

        return getSystemProperty(Constants.STORAGE_BUCKET, StringUtil.EMPTY);
    }

    Integer getLdapMaxUsernameLengthAsInteger();

    default String getLdapSecurityPrincipal(final String username) {
        final String value;
        final int maxLength = getLdapMaxUsernameLengthAsInteger();
        if (username == null) {
            value = StringUtil.EMPTY;