return charMappingService.getCharMappingFile(form.dictId).map(file -> {
            try (InputStream inputStream = form.charMappingFile.getInputStream()) {
                file.update(inputStream);
            } catch (final IOException e) {
                logger.warn("Failed to process a request.", e);
                throwValidationError(messages -> messages.addErrorsFailedToUploadMappingFile(GLOBAL),