Java: A zip in a zip becomes unreadable

Question

For a project I need to create a zip that contains two zip files. I created some methods to do that, however, the resulting zip is not correct.

Consider the following test class:

package nl.test;

import java.io.BufferedOutputStream;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

import org.junit.Test;

public class ZipTest {

    @Test
    public void test() throws IOException {
        Path p = Paths.get("input.txt");
        try (BufferedWriter writer = Files.newBufferedWriter(p)) {
            writer.write("text to compress");
        }
        Path p1 = createZipFile("p.zip", p);
        createZipFile("p1.zip", p1);
    }

    private Path createZipFile(String zipName, Path p) {
        try {
            OutputStream fos = Files.newOutputStream(Paths.get(zipName));
            ZipOutputStream zos = new ZipOutputStream(fos);
            OutputStream bos = new BufferedOutputStream(zos);
            try (Writer writer = new OutputStreamWriter(bos)) {
                zos.putNextEntry(new ZipEntry(p.toString()));
                writer.write(new String(Files.readAllBytes(p)));
                writer.flush();
            }
            return Paths.get(zipName);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

When executing this, the file p1.zip does indeed contain a p.zip, however, that p.zip is unreadable. Is there a way to fix this? Or is there another way to place a zip in a zip?

Answer 1

Here's a simpler way:

1. right click on the file that you want to add in "p.zip"
2. click add to archive and edit the settings if you want to
3. right click anywhere in the folder where p.zip exists and hover your mouse over new and select "Compressed Zipped Folder"
4. after it is created just drag the p.zip into the zipped folder just created now.
5. voilà!

Answer 2

Until I find out why this is not working, it is solved using zip4j:

package nl.test;

import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

import org.junit.Test;

import net.lingala.zip4j.core.ZipFile;
import net.lingala.zip4j.model.ZipParameters;
import net.lingala.zip4j.util.Zip4jConstants;

public class ZipTest2 {

    @Test
    public void test() throws IOException {
        Path p = Paths.get("input.txt");
        try (BufferedWriter writer = Files.newBufferedWriter(p)) {
            writer.write("text to compress");
        }
        Path p1 = createZipFile("p1.zip", p);
        createZipFile("p2.zip", p1);
    }

    private Path createZipFile(String compressedFile, Path inputPath) {
        try {
            ZipFile zipFile = new ZipFile(compressedFile);
            ZipParameters parameters = new ZipParameters();

            parameters.setCompressionMethod(Zip4jConstants.COMP_DEFLATE);
            parameters.setCompressionLevel(Zip4jConstants.DEFLATE_LEVEL_FASTEST);
            zipFile.addFile(inputPath.toFile(), parameters);

            return Paths.get(compressedFile);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

This works when adding a resulting zip to another zip.