public void init(ServletConfig servletConfig) throws ServletException {
   // ##Load Configuration
   // Load SDK configuration for
   // the resource. This intialization code can be
   // done as Init Servlet.
   InputStream is = VoidAuthorizationServlet.class.getResourceAsStream("/sdk_config.properties");
   try {
     PayPalResource.initConfig(is);
   } catch (PayPalRESTException e) {
     LOGGER.fatal(e.getMessage());
   }
 }
  // ##VoidAuthorization
  // Sample showing how to void an Authorization
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    // ###AccessToken
    // Retrieve the access token from
    // OAuthTokenCredential by passing in
    // ClientID and ClientSecret
    APIContext apiContext = null;
    String accessToken = null;
    try {
      accessToken = GenerateAccessToken.getAccessToken();

      // ### Api Context
      // Pass in a `ApiContext` object to authenticate
      // the call and to send a unique request id
      // (that ensures idempotency). The SDK generates
      // a request id if you do not pass one explicitly.
      apiContext = new APIContext(accessToken);
      // Use this variant if you want to pass in a request id
      // that is meaningful in your application, ideally
      // a order id.
      /*
       * String requestId = Long.toString(System.nanoTime(); APIContext
       * apiContext = new APIContext(accessToken, requestId ));
       */

      // ###Authorization
      // Retrieve a Authorization object
      // by making a Payment with intent
      // as 'authorize'
      Authorization authorization = getAuthorization(apiContext);

      // Void an Authorization
      // by POSTing to
      // URI v1/payments/authorization/{authorization_id}/void
      Authorization returnAuthorization = authorization.doVoid(apiContext);

      req.setAttribute("response", Authorization.getLastResponse());
      LOGGER.info(
          "Authorization id = "
              + returnAuthorization.getId()
              + " and status = "
              + returnAuthorization.getState());
    } catch (PayPalRESTException e) {
      req.setAttribute("error", e.getMessage());
    }
    req.getRequestDispatcher("response.jsp").forward(req, resp);
  }