NamedCSVReader add header line number

[sbi1]

Hi, I tested the NamedCSVReader. It works fine if the header is on line 1 of the CSV file. But if the header is on line 2 or any other line number than 1 it does not work. Is it possible to define a starting position e.g. header starts on line 3?

Thank you

[osiegmar]

As defined in section 2.3 of RFC 4180:

There maybe an optional header line appearing as the first line

In section 2.1.3 of current DRAFT RFC 4180-bis this is updated:

The first record in the file MAY be an optional header

followed by section 2.1.8:

[...] A comment line MAY appear in any line of the file (before or after an OPTIONAL header)

This is what the NamedCsvReader supports:

String csv = "# commented line\nheader\nbody\n";

NamedCsvReader.builder()
    .skipComments(true)
    .build(csv)
    .forEach(row -> System.out.println(row.getField("header")));

In order to skip non-RFC-compliant CSV data at the beginning you could use a BufferedReader:

BufferedReader br = new BufferedReader(new StringReader(csv));

// skip arbitrary (non-CSV) data until line break
br.readLine();

NamedCsvReader.builder()
    .build(br)
    .forEach(row -> System.out.println(row.getField("header")));

[osiegmar]

Using FastCSV 3 (soon to be released) this would work:

String csvData = """
    some arbitrary data here
    ...some other here
    header A,header B
    field A,field B
    """;

CsvReader csvReader = CsvReader.builder().build(csvData);

// Read data until you found the actual header
List<String> headerToUse = null;
for (CsvRecord csvRecord : csvReader) {
    if (csvRecord.getField(0).equals("header A")) {
        headerToUse = csvRecord.getFields();
        break;
    }
}

if (headerToUse == null) {
    throw new IllegalStateException("No header found");
}

// Initialize the NamedCsvReader with the header to use
NamedCsvReader namedCsvReader = NamedCsvReader.from(csvReader, headerToUse);

// Use the header / NamedCsvReader
for (NamedCsvRecord namedCsvRecord : namedCsvReader) {
    System.out.println(namedCsvRecord.getField("header A"));
}