source.put("aaa", "");
        source.put("bbb", "a");
        assertFalse(fessConfig.validateIndexRequiredFields(source));
        source.put("aaa", " ");
        source.put("bbb", "a");
        assertFalse(fessConfig.validateIndexRequiredFields(source));
        source.put("aaa", "a");
        source.put("bbb", "a");
        assertTrue(fessConfig.validateIndexRequiredFields(source));

            return new Pair<>(key, value);
        }).collect(Collectors.toMap(Pair::getFirst, Pair::getSecond));
    }

    String getIndexAdminRequiredFields();

    default boolean validateIndexRequiredFields(final Map<String, Object> source) {
        return invalidIndexRequiredFields(source).isEmpty();
    }

    default List<String> invalidIndexRequiredFields(final Map<String, Object> source) {

        final FessConfig fessConfig = ComponentUtil.getFessConfig();

        try {
            if (!fessConfig.validateIndexRequiredFields(doc)) {
                throwError.accept(messages -> fessConfig.invalidIndexRequiredFields(doc)
                        .stream()