Copy directory from a jar file

Thanks for the solution! For others, the following doesn’t make use of the auxiliary classes (except for StringUtils)

/I added extra information for this solution, check the end of the code, Zegor V/

public class FileUtils {
  public static boolean copyFile(final File toCopy, final File destFile) {
    try {
      return FileUtils.copyStream(new FileInputStream(toCopy),
          new FileOutputStream(destFile));
    } catch (final FileNotFoundException e) {
      e.printStackTrace();
    }
    return false;
  }

  private static boolean copyFilesRecusively(final File toCopy,
      final File destDir) {
    assert destDir.isDirectory();

    if (!toCopy.isDirectory()) {
      return FileUtils.copyFile(toCopy, new File(destDir, toCopy.getName()));
    } else {
      final File newDestDir = new File(destDir, toCopy.getName());
      if (!newDestDir.exists() && !newDestDir.mkdir()) {
        return false;
      }
      for (final File child : toCopy.listFiles()) {
        if (!FileUtils.copyFilesRecusively(child, newDestDir)) {
          return false;
        }
      }
    }
    return true;
  }

  public static boolean copyJarResourcesRecursively(final File destDir,
      final JarURLConnection jarConnection) throws IOException {

    final JarFile jarFile = jarConnection.getJarFile();

    for (final Enumeration<JarEntry> e = jarFile.entries(); e.hasMoreElements();) {
      final JarEntry entry = e.nextElement();
      if (entry.getName().startsWith(jarConnection.getEntryName())) {
        final String filename = StringUtils.removeStart(entry.getName(), //
            jarConnection.getEntryName());

        final File f = new File(destDir, filename);
        if (!entry.isDirectory()) {
          final InputStream entryInputStream = jarFile.getInputStream(entry);
          if(!FileUtils.copyStream(entryInputStream, f)){
            return false;
          }
          entryInputStream.close();
        } else {
          if (!FileUtils.ensureDirectoryExists(f)) {
            throw new IOException("Could not create directory: "
                + f.getAbsolutePath());
          }
        }
      }
    }
    return true;
  }

  public static boolean copyResourcesRecursively( //
      final URL originUrl, final File destination) {
    try {
      final URLConnection urlConnection = originUrl.openConnection();
      if (urlConnection instanceof JarURLConnection) {
        return FileUtils.copyJarResourcesRecursively(destination,
            (JarURLConnection) urlConnection);
      } else {
        return FileUtils.copyFilesRecusively(new File(originUrl.getPath()),
            destination);
      }
    } catch (final IOException e) {
      e.printStackTrace();
    }
    return false;
  }

  private static boolean copyStream(final InputStream is, final File f) {
    try {
      return FileUtils.copyStream(is, new FileOutputStream(f));
    } catch (final FileNotFoundException e) {
      e.printStackTrace();
    }
    return false;
  }

  private static boolean copyStream(final InputStream is, final OutputStream os) {
    try {
      final byte[] buf = new byte[1024];

      int len = 0;
      while ((len = is.read(buf)) > 0) {
        os.write(buf, 0, len);
      }
      is.close();
      os.close();
      return true;
    } catch (final IOException e) {
      e.printStackTrace();
    }
    return false;
  }

  private static boolean ensureDirectoryExists(final File f) {
    return f.exists() || f.mkdir();
  }
}

It uses only one external library from the Apache Software Foundation, however the used functions are only :

  public static String removeStart(String str, String remove) {
      if (isEmpty(str) || isEmpty(remove)) {
          return str;
      }
      if (str.startsWith(remove)){
          return str.substring(remove.length());
      }
      return str;
  }
  public static boolean isEmpty(CharSequence cs) {
      return cs == null || cs.length() == 0;
  }

My knowledge is limited on Apache licence, but you can use this methods in your code without library. However, i am not responsible for licence issues, if there is.