code: public Boolean rsa(Map<String, String> notifyParams){
          String expectSign = notifyParams.get(AlipayField.SIGN.field());
          Map<String, String> validParams = filterSigningParams(notifyParams);
          String signing = buildSignString(validParams);
          checkNotNullAndEmpty(alipay.appPubKey, "app public key can't be empty before rsa verify.");
          return RSA.verify(signing, expectSign, alipay.appPubKey, alipay.inputCharset);
      }
docs: RSA验证通知参数是否合法(如APP服务器通知)
  @param notifyParams 通知参数
  @return 合法返回true，反之false