How to create a zip file in Java

Question

Look at this example:

StringBuilder sb = new StringBuilder();
sb.append("Test String");

File f = new File("d:\\test.zip");
ZipOutputStream out = new ZipOutputStream(new FileOutputStream(f));
ZipEntry e = new ZipEntry("mytext.txt");
out.putNextEntry(e);

byte[] data = sb.toString().getBytes();
out.write(data, 0, data.length);
out.closeEntry();

out.close();

This will create a zip in the root of D: named test.zip which will contain one single file called mytext.txt. Of course you can add more zip entries and also specify a subdirectory like this:

ZipEntry e = new ZipEntry("folderName/mytext.txt");

You can find more information about compression with Java here.

Java 7 has ZipFileSystem built in, that can be used to create, write and read file from zip file.

Java Doc: ZipFileSystem Provider

Map<String, String> env = new HashMap<>();
// Create the zip file if it doesn't exist
env.put("create", "true");

URI uri = URI.create("jar:file:/codeSamples/zipfs/zipfstest.zip");

try (FileSystem zipfs = FileSystems.newFileSystem(uri, env)) {
    Path externalTxtFile = Paths.get("/codeSamples/zipfs/SomeTextFile.txt");
    Path pathInZipfile = zipfs.getPath("/SomeTextFile.txt");          
    // Copy a file into the zip file
    Files.copy(externalTxtFile, pathInZipfile, StandardCopyOption.REPLACE_EXISTING); 
}

To write a ZIP file, you use a ZipOutputStream. For each entry that you want to place into the ZIP file, you create a ZipEntry object. You pass the file name to the ZipEntry constructor; it sets the other parameters such as file date and decompression method. You can override these settings if you like. Then, you call the putNextEntry method of the ZipOutputStream to begin writing a new file. Send the file data to the ZIP stream. When you are done, call closeEntry. Repeat for all the files you want to store. Here is a code skeleton:

FileOutputStream fout = new FileOutputStream("test.zip");
ZipOutputStream zout = new ZipOutputStream(fout);
for all files
{
    ZipEntry ze = new ZipEntry(filename);
    zout.putNextEntry(ze);
    send data to zout;
    zout.closeEntry();
}
zout.close();

Here is an example code to compress a Whole Directory(including sub files and sub directories), it's using the walk file tree feature of Java NIO.

import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class ZipCompress {
    public static void compress(String dirPath) {
        final Path sourceDir = Paths.get(dirPath);
        String zipFileName = dirPath.concat(".zip");
        try {
            final ZipOutputStream outputStream = new ZipOutputStream(new FileOutputStream(zipFileName));
            Files.walkFileTree(sourceDir, new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult visitFile(Path file, BasicFileAttributes attributes) {
                    try {
                        Path targetFile = sourceDir.relativize(file);
                        outputStream.putNextEntry(new ZipEntry(targetFile.toString()));
                        byte[] bytes = Files.readAllBytes(file);
                        outputStream.write(bytes, 0, bytes.length);
                        outputStream.closeEntry();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    return FileVisitResult.CONTINUE;
                }
            });
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

To use this, just call

ZipCompress.compress("target/directoryToCompress");

and you'll get a zip file directoryToCompress.zip

Spring boot controller, zip the files in a directory, and can be downloaded.

@RequestMapping(value = "/files.zip")
@ResponseBody
byte[] filesZip() throws IOException {
    File dir = new File("./");
    File[] filesArray = dir.listFiles();
    if (filesArray == null || filesArray.length == 0)
        System.out.println(dir.getAbsolutePath() + " have no file!");
    ByteArrayOutputStream bo = new ByteArrayOutputStream();
    ZipOutputStream zipOut= new ZipOutputStream(bo);
    for(File xlsFile:filesArray){
        if(!xlsFile.isFile())continue;
        ZipEntry zipEntry = new ZipEntry(xlsFile.getName());
        zipOut.putNextEntry(zipEntry);
        zipOut.write(IOUtils.toByteArray(new FileInputStream(xlsFile)));
        zipOut.closeEntry();
    }
    zipOut.close();
    return bo.toByteArray();
}