使用微信支付接口退款

准备工作

微信支付开发文档：https://pay.weixin.qq.com/docs/merchant/apis/jsapi-payment/create.html

退款与查单的请求头类似，但是查单是GET请求，所以在构造签名的时候相对简单些，但是退款请求中有请求参数，在构造签名时，需要将请求体添加到请求头参数中。

开始开发

1、构造请求参数

查看微信支付开发文档，请求参数中refund_id/out_refund_no，transaction_id/out_trade_no这两个参数，一个是微信支付系统中的退款号以及订单号，一个是自己的系统中的退款号以及订单号，这里我们使用后者；其次必填的参数还有refund、total、currency、amount

		//构造请求参数
        Map data = new HashMap();
        data.put("out_trade_no", orderDao.getOrder_no());
        data.put("out_refund_no", orderDao.getRefund_order_no());
        Map amount = new HashMap();
        amount.put("refund", (int) (Double.parseDouble(orderDao.getPrice()) * 100));
        amount.put("total", (int) (Double.parseDouble(orderDao.getPrice()) * 100));
        amount.put("currency", "CNY");
        data.put("amount", amount);

2.构造请求头签名（具体方法类可以查看博主上篇文章）

⚠️：与查单不同的是，退款借口是post请求并且携带参数，在构建请求头签名时，getToken()中的第三个参数是请求体的json类型

		String schema = "WECHATPAY2-SHA256-RSA2048 ";
        HttpUrl httpurl = HttpUrl.parse("https://api.mch.weixin.qq.com/v3/refund/domestic/refunds");
        // 设置请求链接
        HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/v3/refund/domestic/refunds");
        //设置请求头信息
        httpPost.setHeader("Authorization", schema + getToken("POST", httpurl, JSONObject.toJSONString(data)));
        httpPost.setHeader("Accept", "application/json");
        httpPost.setHeader("Content-Type", "application/json");
        httpPost.setEntity(new StringEntity(JSONObject.toJSONString(data)));
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        CloseableHttpResponse response = httpClient.execute(httpPost);
        // 获取响应状态码
        int statusCode = response.getStatusLine().getStatusCode();
        // 获取响应内容
        String responseBody = EntityUtils.toString(response.getEntity());
        // 关闭响应对象
        response.close();
        map.put("code", statusCode);
        map.put("data", responseBody);

3.完整接口代码

	@PostMapping("/refund_order")
    public Map refund_order(@RequestBody OrderDao orderDao) throws IOException, SignatureException, NoSuchAlgorithmException, InvalidKeyException {
    
        Map map = new HashMap<>();
        //构造请求参数
        Map data = new HashMap();
        data.put("out_trade_no", orderDao.getOrder_no());
        data.put("out_refund_no", orderDao.getRefund_order_no());
        Map amount = new HashMap();
        amount.put("refund", (int) (Double.parseDouble(orderDao.getPrice()) * 100)); // 我存的是string类型的单位为元的价格，所以需要转换成整形单位为分
        amount.put("total", (int) (Double.parseDouble(orderDao.getPrice()) * 100)); 
        amount.put("currency", "CNY");
        data.put("amount", amount);
        String schema = "WECHATPAY2-SHA256-RSA2048 "; //注意有一个空格
        HttpUrl httpurl = HttpUrl.parse("https://api.mch.weixin.qq.com/v3/refund/domestic/refunds");
        // 设置请求链接
        HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/v3/refund/domestic/refunds");
        //设置请求头信息
        httpPost.setHeader("Authorization", schema + getToken("POST", httpurl, JSONObject.toJSONString(data)));
        httpPost.setHeader("Accept", "application/json");
        httpPost.setHeader("Content-Type", "application/json");
        httpPost.setEntity(new StringEntity(JSONObject.toJSONString(data))); //设置请求参数
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        CloseableHttpResponse response = httpClient.execute(httpPost);
        // 获取响应状态码
        int statusCode = response.getStatusLine().getStatusCode();
        // 获取响应内容
        String responseBody = EntityUtils.toString(response.getEntity());
        // 关闭响应对象
        response.close();
        map.put("code", statusCode);
        map.put("data", responseBody);
        return map;
    }

4.apifox测试结果