private RowDataToFieldConverter createDateConverter() {
        return inputObj -> {
            int days = (int) inputObj;
            LocalDate localDate = LocalDate.ofEpochDay(days);
            return ISO_LOCAL_DATE.format(localDate);
        };
    }
Creates a runtime converter which assuming input object is not null.
inlong-sort/sort-formats/format-rowdata/format-rowdata-json/src/main/java/org/apache/inlong/sort/formats/json/RowDataToFieldConverters.java