Compressed CSV

CSV files are typically used as uncompressed files. However, compressing CSV files can be advantageous, especially for larger files, as it saves disk space and reduces transfer times. Depending on the system’s I/O performance, working with compressed CSV files can also speed up data processing.

Example

The following example demonstrates how to write and read CSV files with FastCSV using GZIP compression:

ExampleCsvCompression.java

package example;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import de.siegmar.fastcsv.reader.CsvReader;
import de.siegmar.fastcsv.writer.CsvWriter;

/**
 * Example for writing and reading compressed CSV data.
 */
public class ExampleCsvCompression {

    public static void main(final String[] args) throws IOException {
        final Path file = Files.createTempFile("fastcsv", ".csv.gz");
        file.toFile().deleteOnExit();

        System.out.println(file.toAbsolutePath());

        writeCsvGzipped(file);
        readCsvGzipped(file);
    }

    private static void writeCsvGzipped(final Path file) throws IOException {
        try (var csv = CsvWriter.builder().build(gzipWriter(file))) {
            csv.writeRecord("header1", "header2");
            csv.writeRecord("value1", "value2");
        }
    }

    private static OutputStreamWriter gzipWriter(final Path file)
        throws IOException {
        final var bufOut = new BufferedOutputStream(Files.newOutputStream(file));
        final var gzipOut = new GZIPOutputStream(bufOut);
        return new OutputStreamWriter(gzipOut, UTF_8);
    }

    private static void readCsvGzipped(final Path file) throws IOException {
        System.out.println("Reading compressed CSV file:");

        try (var csv = CsvReader.builder().ofCsvRecord(gzipReader(file))) {
            csv.forEach(System.out::println);
        }
    }

    private static Reader gzipReader(final Path file) throws IOException {
        final var bufIn = new BufferedInputStream(Files.newInputStream(file));
        final var gzipIn = new GZIPInputStream(bufIn);
        return new InputStreamReader(gzipIn, UTF_8);
    }

}

You also find this source code example in the FastCSV GitHub repository.