Importing only specific columns from CSV file

Question

I'm trying to import CSV files using Java library openCSV. Is there any way to load only specific columns not all of them? My code right now is:

JFileChooser fileopen = new JFileChooser();
                FileFilter filter = new FileNameExtensionFilter(
                        "CSV file", "csv");
                fileopen.addChoosableFileFilter(filter);

                int ret = fileopen.showDialog(null, "Choose file");
                                if (ret == JFileChooser.APPROVE_OPTION) {
    try {
        File file = fileopen.getSelectedFile();
        System.out.println("Opening: " + file.getName());
        File csvFilename = fileopen.getSelectedFile();
        try (CSVReader csvReader = new CSVReader(new FileReader(csvFilename), ',', '\'',11 )) {
            String[] row = null;
            while((row = csvReader.readNext()) != null) {
                System.out.println(row[0]
                        + " # " + row[1]
                        + " #  " + row[2]);
            }
        } 
    } catch (FileNotFoundException ex) {
        Logger.getLogger(Glass_search.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(Glass_search.class.getName()).log(Level.SEVERE, null, ex);
    }

    }

This file also got headings so maybe this way?

Jeronimo Backes · Accepted Answer · 2018-03-17 08:46:08Z

1

For that particular case univocity-parsers is a much better fit as you can easily choose what columns to get:

CsvParserSettings parserSettings = new CsvParserSettings();
settings.detectFormatAutomatically(); //detects the format 

//extracts the headers from the input
settings.setHeaderExtractionEnabled(true);

//or give the header names yourself
// if you use this it will override the headers read from the input (enabled above).
settings.setHeaders("A", "B", "C");

//now for the column selection
settings.selectFields("A", "C"); //rows will contain only values of column "A" and "C"
//or
settings.selectIndexes(0, 2); //rows will contain only values of columns at position 0 and 2

List<String[]> rows = new CsvParser(settings).parseAll(new File("/path/to/your.csv"), "UTF-8");

You can also get the values of each column in a List:

ColumnProcessor columnProcessor = new ColumnProcessor();
settings.setProcessor(columnProcessor);
CsvParser parser = new CsvParser(settings);
parser.parse(new File("/path/to/your.csv), "UTF-8"); //all rows are submitted to the processor created above.

Map<String, List<String>> columnValues = columnProcessor.getColumnValuesAsMapOfNames();

This should solve all your problems, hope it helps.

Disclaimer: I'm the author of this library. It's open-source and free (Apache 2.0 license)

answered Mar 17, 2018 at 8:46

Jeronimo Backes

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1 Comment

n0rek Over a year ago

First one works just perfect, now I'm trying to use file from JFileChooser and upload it to MSSQL database :) Thank you. Your library saved me a lot work.

Joakim Danielson · Accepted Answer · 2018-03-14 13:58:30Z

1

If you create your CSVReader instance using a CSVReaderBuilder you can set your own parser for the reader to use. All you need then is to create your own parser that implements the ICSVParser interface.

answered Mar 14, 2018 at 13:58

Joakim Danielson

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1 Comment

n0rek Over a year ago

ahh crap, that's not my level of exp yet ;) Thanks anyway

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