@GET
@Path("/start")
public void start(@Context HttpServletRequest request, @Context HttpServletResponse response) throws IOException {

    String url = initFlow().newAuthorizationUrl().setRedirectUri("http://localhost:8080/GDriveRest/app/gdrive/finish").build();
    response.sendRedirect(url);
}

@GET
@Path("/finish")
public void finish(@Context HttpServletRequest request, @Context HttpServletResponse response) throws IOException {

    AuthorizationCodeFlow flow = initFlow();
    flow.newTokenRequest(request.getParameter("code"));

    response.sendRedirect("http://m.memegen.com/1yx6o5.jpg?"+request.getParameter("code")+"&id="+flow.getClientId());
}

private AuthorizationCodeFlow initFlow() throws IOException {

    InputStream in = GDrive.class.getResourceAsStream("/client_secret.json");
    GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY, new InputStreamReader(in));

    return new GoogleAuthorizationCodeFlow.Builder(new NetHttpTransport(),
                                                   JacksonFactory.getDefaultInstance(),
                                                   clientSecrets, SCOPES).setAccessType("offline").build();
}