PrepayRequest prepayRequest = new PrepayRequest();
Amount amount = new Amount();
amount.setCurrency("CNY");
amount.setTotal(payOrderExist.getPayFee());
prepayRequest.setAmount(amount);
prepayRequest.setAppid("xx");///这个是什么appid??
prepayRequest.setMchid(MERCHANT_ID);
prepayRequest.setDescription(desc);
prepayRequest.setNotifyUrl(serverHost + "/api/order/app/pay/callback");
prepayRequest.setOutTradeNo(String.valueOf(payOrderExist.getId()));
PrepayResponse prepayResponse = appService.prepay(prepayRequest)
APP支付需要使用移动应用APPID
你通过什么下单的就是哪个的appid,比如微信小程序下单的就需要微信小程序的APPID,公众号就得用公众号的