[JAVA WEB]SpringBoot实现微信V3支付（JSAPI版）

工具类采用：Hutool依赖

// 微信V3支付
public JSONObject wechatPayJsApi() throws Exception {
    String url = StrUtil.format("https://api.mch.weixin.qq.com/v3/pay/transactions/jsapi");
    String appid = "微信公众号appid";
    String mchId = "微信商户mchid";
    String notifyUrl = "支付成功回调地址";
    String nonceStr = IdUtil.simpleUUID();
    String timestamp = System.currentTimeMillis() / 1000; 
    JSONObject jsonObject = new JSONObject();
    jsonObject.set("appid", appid);
    jsonObject.set("mchid", mchId);
    jsonObject.set("description", "商品的名称");
    jsonObject.set("out_trade_no", DateUtil.format(LocalDateTime.now(), "yyyyMMddHHmmssSSS"));
    jsonObject.set("notify_url", notifyUrl);

    jsonObject.set("amount",
            new JSONObject()
                    .set("total", 金额(分))
    );
    jsonObject.set("scene_info",
            new JSONObject()
                    .set("payer_client_ip", "支付的ip")
    );
    jsonObject.set("payer",
            new JSONObject()
                    .set("openid", "微信用户openId")
    );

    HttpResponse execute = HttpUtil.createPost(url)
            .header("Content-Type", "application/json;chartset=utf-8")
            .header("Accept", "application/json")
            .header("Authorization", getToken("POST", new URL(url), jsonObject.toString()))
            .body(jsonObject.toString())
            .execute();
    if(execute.getStatus() != 200) {
        log.info("微信支付错误信息：" + execute.body());
        return execute.body();
    } else {
        String jsonResult = execute.body();
        boolean isJson = JSONUtil.isJson(jsonResult);
        if (!isJson) {
            log.info("payJSAPI 错误的返回值：" + jsonResult);
            return jsonResult;
        }
        JSONObject json = JSONUtil.parseObj(jsonResult);
        if (null == json.getStr("prepay_id")) {
            log.info("payJSAPI 错误的返回值：" + jsonResult);
            return jsonResult;
        }

        String packageStr = "prepay_id=" + json.getStr("prepay_id");
        String message = StrUtil.format("{}\n{}\n{}\n{}\n",
                APP_ID, timestamp, nonceStr, packageStr);
        String signature = sign(message.getBytes(StandardCharsets.UTF_8));
        // 组装返回
        JSONObject result = new JSONObject();
        result.set("appId", APP_ID);
        result.set("timeStamp", String.valueOf(timestamp));
        result.set("nonceStr", nonceStr);
        result.set("package", packageStr);
        result.set("signType", "RSA");
        result.set("paySign", signature);
        return result.toString();
    }
}

// 生成签名
public static String getToken(String method, URL url, String body) throws Exception {
    String message = buildMessage(method, url, timestamp, nonceStr, body);
    String signature = sign(message.getBytes(StandardCharsets.UTF_8));

    return StrUtil.format("WECHATPAY2-SHA256-RSA2048 mchid=\"{}\",nonce_str=\"{}\",timestamp=\"{}\",serial_no=\"{}\",signature=\"{}\"",
            MCH_ID, nonceStr, timestamp, MERCHANT_SERIAL_NUMBER, signature);
}
// 组合签名
public static String buildMessage(String method, URL url, long timestamp, String nonceStr, String body) {
    String canonicalUrl = url.getPath();
    if (url.getQuery() != null) { canonicalUrl += "?" + url.getQuery(); }
    return StrUtil.format("{}\n{}\n{}\n{}\n{}\n",
            method, canonicalUrl, timestamp, nonceStr, body);
}
// 获取证书
private static String sign(byte[] message) throws NoSuchAlgorithmException, SignatureException, IOException, InvalidKeyException {
    Signature sign = Signature.getInstance("SHA256withRSA"); //SHA256withRSA
    sign.initSign(getPrivateKey("你的商务支付证书目录/apiclient_key.pem"));
    sign.update(message);
    return Base64.getEncoder().encodeToString(sign.sign());
}
// 获取私钥
public static PrivateKey getPrivateKey(String filename) throws IOException {
    String content = new String(Files.readAllBytes(Paths.get(filename)), StandardCharsets.UTF_8);

    try {
        String privateKey = content.replace("-----BEGIN PRIVATE KEY-----", "")
                .replace("-----END PRIVATE KEY-----", "")
                .replaceAll("\\s+", "");

        KeyFactory kf = KeyFactory.getInstance("RSA");
        return kf.generatePrivate(new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKey)));
    } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("当前Java环境不支持RSA", e);
    } catch (InvalidKeySpecException e) {
        throw new RuntimeException("无效的密钥格式");
    }
}