private static void downloadFileFromURL(String urlString, File destination) throws Exception {
    if (System.getenv("MVNW_USERNAME") != null && System.getenv("MVNW_PASSWORD") != null) {
      String username = System.getenv("MVNW_USERNAME");
      char[] password = System.getenv("MVNW_PASSWORD").toCharArray();
      Authenticator.setDefault(new Authenticator() {
        @Override
        protected PasswordAuthentication getPasswordAuthentication() {
          return new PasswordAuthentication(username, password);
        }
      });
    }
    URL website = new URL(urlString);
    ReadableByteChannel rbc;
    rbc = Channels.newChannel(website.openStream());
    FileOutputStream fos = new FileOutputStream(destination);
    fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
    fos.close();
    rbc.close();
  }
Name of the property which should be used to override the default download url for the wrapper.
.mvn/wrapper/MavenWrapperDownloader.java