微信支付开发文档地址：https://pay.weixin.qq.com/wiki/doc/api/index.html

一、应用场景

线下场所付款方式：（便利店、自动贩卖机）
1、顾客出示二维码，店员用扫码枪进行扫码
2、展示二维码，让顾客进行扫码支付
公众号付款方式:
app付款方式:做第三方应用（app），可以集成微信支付功能，由app 去调微信支付功能，就可以进行支付了
PC网站付款方式：网站展示二维码，让顾客进行扫码支付

二、开发准备

先登录，获取openid

三、开发流程

调用统一下单支付api

CreateOrderRequestVo unifiedorderVo = getUnifiedorderVo(weixinPay,                     "o8C3f5VUxyZGd58JxDi38q5JrTjo", clientIp, appId, mchId, signKey);
CreateOrderResponseVo responseVo = unifiedOrder(unifiedorderVo);

/**
     * 获取微信预下单对象(JSAPI支付)
     * @return 微信预下单对象
     */
    private CreateOrderRequestVo getUnifiedorderVo(WeixinPay weixinPay, String openid, String ip, String appId, String mchId, String signKey) {
        // 获取域名
        String domain = systemConfigService.getValueByKeyException(Constants.CONFIG_KEY_SITE_URL);
        String apiDomain = systemConfigService.getValueByKeyException(Constants.CONFIG_KEY_API_URL);
        AttachVo attachVo = new AttachVo(Constants.Small_Shop_Settle_Pay, weixinPay.getUid());
        CreateOrderRequestVo vo = new CreateOrderRequestVo();
//       List<StoreOrderInfo> orderInfoList = storeOrderInfoService.getListByOrderNo(storeOrder.getOrderId());
        vo.setAppid(appId);
        vo.setMch_id(mchId);
        vo.setNonce_str(WxPayUtil.getNonceStr());
        vo.setSign_type(PayConstants.WX_PAY_SIGN_TYPE_MD5);
//        vo.setBody(PayConstants.PAY_BODY);
//        vo.setBody(orderInfoList.get(0).getProductName());
        String siteName = systemConfigService.getValueByKeyException(Constants.CONFIG_KEY_SITE_NAME);
        // 因商品名称在微信侧超长更换为网站名称
        vo.setBody(siteName);
        vo.setAttach(JSONObject.toJSONString(attachVo));
        vo.setOut_trade_no(CrmebUtil.getOrderNo("wxNo"));
        // 订单中使用的是BigDecimal,这里要转为Integer类型
        vo.setTotal_fee(weixinPay.getPayPrice().multiply(BigDecimal.TEN).multiply(BigDecimal.TEN).intValue());
        vo.setSpbill_create_ip(ip);
        vo.setNotify_url(apiDomain + PayConstants.WX_PAY_NOTIFY_API_URI);
        if (weixinPay.getPaymentChannel().equals(PayConstants.PAY_CHANNEL_WE_CHAT_H5)){// H5
            vo.setTrade_type(PayConstants.WX_PAY_TRADE_TYPE_H5);
            vo.setOpenid(null);
        }
        if (weixinPay.getPaymentChannel().equals(PayConstants.PAY_CHANNEL_WE_CHAT_PROGRAM)){// 小程序
            vo.setTrade_type(PayConstants.WX_PAY_TRADE_TYPE_JS);
            vo.setOpenid(openid);
        }
        if (weixinPay.getPaymentChannel().equals(PayConstants.PAY_CHANNEL_WE_CHAT_APP_IOS) || weixinPay.getPaymentChannel().equals(PayConstants.PAY_CHANNEL_WE_CHAT_APP_ANDROID)) {
            vo.setTrade_type("APP");
            vo.setOpenid(null);
        }
        CreateOrderH5SceneInfoVo createOrderH5SceneInfoVo = new CreateOrderH5SceneInfoVo(
                new CreateOrderH5SceneInfoDetailVo(
                        domain,
                        systemConfigService.getValueByKeyException(Constants.CONFIG_KEY_SITE_NAME)
                )
        );
        vo.setScene_info(JSONObject.toJSONString(createOrderH5SceneInfoVo));
        String sign = WxPayUtil.getSign(vo, signKey);
        vo.setSign(sign);
        vo.setSmallShopSettledPayRequest(weixinPay.getSmallShopSettledPayRequest());
        return vo;
    }

private CreateOrderResponseVo unifiedOrder(CreateOrderRequestVo unifiedorderVo) {
    try {
        String url = PayConstants.WX_PAY_API_URL + PayConstants.WX_PAY_API_URI;
        String request = XmlUtil.objectToXml(unifiedorderVo);
        String xml = restTemplateUtil.postXml(url, request);
        HashMap<String, Object> map = XmlUtil.xmlToMap(xml);
        if (null == map) {
            throw new CrmebException("微信下单失败！");
        }
CreateOrderResponseVo responseVo = CrmebUtil.mapToObj(map, CreateOrderResponseVo.class);
    return responseVo;
    } catch (Exception e) {
        e.printStackTrace();
        throw new CrmebException(e.getMessage());
    }
}