Today i had a requirement to compress and extract list of files to a tar file in Java.

Googling over net and found this library http://www.trustice.com/java/tar/ . I couldnt find the examples for using the library.

Tried out a bit and got it up working. So just posting out the code that could compress and extract files to/from a TAR File.

Compressing files to Tar File :

private File compressFilesToTarFile(List files) throws Exception {
 TarEntry tarEntry = null;
 File tarFile = new File(CommonConstants.ROOT_BACKUP_FOLDER+File.separator+CommonConstants.LOGS_BACKUP_FOLDER+File.separator +buildGeneratedTarFileName());
 tarFile.createNewFile();
 OutputStream outputStream = new FileOutputStream(tarFile);
 TarOutputStream tarOutputStream = new TarOutputStream(outputStream);
 for(File file : files)
 {
 tarEntry = new TarEntry(file);
 tarOutputStream.putNextEntry(tarEntry);
 tarOutputStream.write(getBytesFromFile(file));
 tarOutputStream.closeEntry();
 }
 tarOutputStream.close();
 return tarFile;
}

private static byte[] getBytesFromFile(File file) throws Exception {
 InputStream is = new FileInputStream(file);
 // Get the size of the file
 long length = file.length();
 if (length > Integer.MAX_VALUE) {
    // File is too large
}
 // Create the byte array to hold the data
 byte[] bytes = new byte[(int)length];
 // Read in the bytes
 int offset = 0;
 int numRead = 0;
 while (offset <bytes.length  && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
      offset += numRead;
 }
 // Ensure all the bytes have been read in
 if (offset <bytes.length) {
  throw new Exception("Could not completely read file "+file.getName());
 }
 // Close the input stream and return bytes
 is.close();
 return bytes;
}

Extracting files from Tar File

private static void untarBaseUpgradeFile(File tarFile, File dest) throws Exception
{
dest.mkdir();
TarInputStream tin = new TarInputStream(new GZIPInputStream(new FileInputStream(tarFile)));
TarEntry tarEntry = tin.getNextEntry();
while (tarEntry != null)
{
  File destPath = new File(dest.toString() + File.separatorChar + tarEntry.getName());
  if (tarEntry.isDirectory()) {
    destPath.mkdir();
  }
  else {
    FileOutputStream fout = new FileOutputStream(destPath);
    tin.copyEntryContents(fout);
    fout.close();
  }
  tarEntry = tin.getNextEntry();
}
tin.close(); tin = null;
}