FileUploadServiceImpl_getLines.java

public Flux<String> getLines(Flux<FilePart> filePartFlux) {

    return filePartFlux.flatMap(filePart ->
            filePart.content().map(dataBuffer -> {
                byte[] bytes = new byte[dataBuffer.readableByteCount()];
                dataBuffer.read(bytes);
                DataBufferUtils.release(dataBuffer);

                return new String(bytes, StandardCharsets.UTF_8);
            })
            .map(this::processAndGetLinesAsList)
            .flatMapIterable(Function.identity());
}