Comprimere e decomprimere file tar.gz con Java

Java di default non ha classi per la compressione / decompressione dei file tar.gz.

Però possiamo usare Apache Commons Compress.

Se usate Maven:

<dependencies>
	<dependency>
		<groupId>org.apache.commons</groupId>
		<artifactId>commons-compress</artifactId>
		<version>1.20</version>
	</dependency>
</dependencies>

Qui sotto un codice con le due funzioni:

import org.apache.commons.compress.archivers.ArchiveEntry;
import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
import org.apache.commons.compress.archivers.tar.TarArchiveOutputStream;
import org.apache.commons.compress.compressors.gzip.GzipCompressorInputStream;
import org.apache.commons.compress.compressors.gzip.GzipCompressorOutputStream;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;

public class Main {

    public static void main(String[] args) {
        Path pathOut = Paths.get("/home/user/file.tar.gz");
        Path pathInput = Paths.get("/home/user/file.xls");
        Path target = Paths.get("/home/user/test_comp");

        try {
            compress(pathInput, pathOut);
        } catch (IOException ex) {
            System.out.println("ERR: " + ex.getMessage());
        }

        System.out.println("COMPRESSIONE OK");

        try {
            decompress(pathOut, target);
        } catch (IOException ex) {
            System.out.println("ERR: " + ex.getMessage());
        }

        System.out.println("DE-COMPRESSIONE OK");
    }

    private static void compress(Path input, Path output) throws IOException {
        try (OutputStream fOut = Files.newOutputStream(output);
             BufferedOutputStream buffOut = new BufferedOutputStream(fOut);
             GzipCompressorOutputStream gzOut = new GzipCompressorOutputStream(buffOut);
             TarArchiveOutputStream tOut = new TarArchiveOutputStream(gzOut)) {

            TarArchiveEntry tarEntry = new TarArchiveEntry(input.toFile(), input.getFileName().toString());
            tOut.putArchiveEntry(tarEntry);
            Files.copy(input, tOut);
            tOut.closeArchiveEntry();

            tOut.finish();
        }
    }

    private static void decompress(Path input, Path output) throws IOException {
        try (InputStream fi = Files.newInputStream(input);
             BufferedInputStream bi = new BufferedInputStream(fi);
             GzipCompressorInputStream gzi = new GzipCompressorInputStream(bi);
             TarArchiveInputStream ti = new TarArchiveInputStream(gzi)) {

            ArchiveEntry entry;
            while ((entry = ti.getNextEntry()) != null) {
                Path targetDirResolved = output.resolve(entry.getName());
                Path normalizePath = targetDirResolved.normalize();

                if (entry.isDirectory()) {
                    Files.createDirectories(normalizePath);
                } else {
                    Path parent = normalizePath.getParent();
                    if (parent != null) {
                        if (Files.notExists(parent)) {
                            Files.createDirectories(parent);
                        }
                    }

                    Files.copy(ti, normalizePath, StandardCopyOption.REPLACE_EXISTING);
                }
            }
        }
    }

}

Enjoy!