How to unzip files recursively in Java?

Question

I have zip file which contains some other zip files.

For example, the mail file is abc.zip and it contains xyz.zip, class1.java, class2.java. And xyz.zip contains the file class3.java and class4.java.

So I need to extract the zip file using Java to a folder that should contain class1.java, class2.java, class3.java and class4.java.

Answer 1

Warning, the code here is ok for trusted zip files, there's no path validation before write which may lead to security vulnerability as described in zip-slip-vulnerability if you use it to deflate an uploaded zip file from unknown client.

---

This solution is very similar to the previous solutions already posted, but this one recreates the proper folder structure on unzip.

public static void extractFolder(String zipFile) throws IOException {
int buffer = 2048;
File file = new File(zipFile);

try (ZipFile zip = new ZipFile(file)) {
  String newPath = zipFile.substring(0, zipFile.length() - 4);

  new File(newPath).mkdir();
  Enumeration<? extends ZipEntry> zipFileEntries = zip.entries();

  // Process each entry
  while (zipFileEntries.hasMoreElements()) {
    // grab a zip file entry
    ZipEntry entry = zipFileEntries.nextElement();
    String currentEntry = entry.getName();
    File destFile = new File(newPath, currentEntry);
    File destinationParent = destFile.getParentFile();

    // create the parent directory structure if needed
    destinationParent.mkdirs();

    if (!entry.isDirectory()) {
      BufferedInputStream is = new BufferedInputStream(zip.getInputStream(entry));
      int currentByte;
      // establish buffer for writing file
      byte[] data = new byte[buffer];

      // write the current file to disk
      FileOutputStream fos = new FileOutputStream(destFile);
      try (BufferedOutputStream dest = new BufferedOutputStream(fos, buffer)) {

        // read and write until last byte is encountered
        while ((currentByte = is.read(data, 0, buffer)) != -1) {
          dest.write(data, 0, currentByte);
        }
        dest.flush();
        is.close();
      }
    }

    if (currentEntry.endsWith(".zip")) {
      // found a zip file, try to open
      extractFolder(destFile.getAbsolutePath());
    }
  }
}

}