商家转账到零钱为商户提供同时向多个用户微信零钱转账的能力，具有高效、免费、快速到账、安全等优点。

示例

pom文件中引入

            <!-- https://mvnrepository.com/artifact/cn.hutool/hutool-all -->
            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>5.8.10</version>
            </dependency>

代码

    public String transferAccounts() {
        // 商户号
        String mchid = "商户号";
        // 商户证书路径（在你本机测试时放你本机路径中的就可以）
        Map<String, Object> postMap = new HashMap<>();
        // 申请商户号的appid或商户号绑定的appid（企业号corpid即为此appid）
        postMap.put("appid", "appid");
        // 商家批次单号 长度 1~32
        postMap.put("out_batch_no", IdUtil.getSnowflake(0, 0).nextIdStr());
        // 该笔批量转账的名称
        postMap.put("batch_name", "测试转账");
        // 转账说明，UTF8编码，最多允许32个字符
        postMap.put("batch_remark", "测试转账");
        // 总金额 单位为“分”
        postMap.put("total_amount", 10);
        // 转账总笔数
        postMap.put("total_num", 1);
        // 转账明细列表
        List<Map<String, Object>> list = new ArrayList<>();
        // 转账明细
        Map<String, Object> subMap = new HashMap<>(4);
        // 商家批次单号
        subMap.put("out_detail_no", IdUtil.getSnowflake(0, 0).nextIdStr());
        // 转账金额
        subMap.put("transfer_amount", 10);
        // 转账备注
        subMap.put("transfer_remark", "明细备注");
        // 用户在直连商户应用下的用户标示
        subMap.put("openid", "openid");
        list.add(subMap);
        postMap.put("transfer_detail_list", list);
        // 发起转账操作
        return postTransBatRequest(JSON.toJSONString(postMap), mchid);
    }

    /**
     * 发起批量转账API 批量转账到零钱
     * 证书下载地址：需要指到文件 例如：D:\XXX.pem
     *
     * @param requestJson       组合参数
     * @param mchID4M           商户号
     * @return String
     */
    public static String postTransBatRequest(String requestJson, String mchID4M) {
        try {
            CloseableHttpClient httpclient = HttpClients.createDefault();
            HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/v3/transfer/batches");
            // NOTE: 建议指定charset=utf-8。低于4.4.6版本的HttpCore，不能正确的设置字符集，可能导致签名错误
            httpPost.addHeader("Content-Type", "application/json");
            httpPost.addHeader("Accept", "application/json");
            // 文档证书序列号
            httpPost.addHeader("Wechatpay-Serial", "文档证书序列号");
            // -------------------------核心认证 start-----------------------------------------------------------------
            String strToken = getToken("POST",
                    "/v3/transfer/batches",
                    requestJson, mchID4M, "文档证书序列号", "证书下载地址");
            // 添加认证信息
            httpPost.addHeader("Authorization", "WECHATPAY2-SHA256-RSA2048 " + strToken);
            // ---------------------------核心认证 end---------------------------------------------------------------
            httpPost.setEntity(new StringEntity(requestJson, "UTF-8"));
            // 发起转账请求
            CloseableHttpResponse response = httpclient.execute(httpPost);
            // 获取返回的数据
            HttpEntity entity = response.getEntity();
            return EntityUtils.toString(entity);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * @param method       请求方法 post
     * @param canonicalUrl 请求地址
     * @param body         请求参数
     * @param merchantId   这里用的商户号
     * @param certSerialNo 商户证书序列号
     * @param keyPath      商户证书地址
     * @return String
     */
    public static String getToken(String method, String canonicalUrl, String body, String merchantId,
                                  String certSerialNo, String keyPath) throws Exception {
        // 获取32位随机字符串
        String nonceStr = getRandomString(32);
        // 当前系统运行时间
        long timestamp = System.currentTimeMillis() / 1000;
        if (StringUtils.isEmpty(body)) body = "";
        String message = method + "\n" + canonicalUrl + "\n" + timestamp + "\n" + nonceStr + "\n" + body + "\n";
        // 签名操作
        Signature sign = Signature.getInstance("SHA256withRSA");
        sign.initSign(getPrivateKey(keyPath));
        sign.update(message.getBytes(StandardCharsets.UTF_8));
        String signature =  Base64.encodeBase64String(sign.sign());
        // 组装参数
        return "mchid=\"" + merchantId + "\",timestamp=\"" + timestamp + "\",nonce_str=\"" + nonceStr +
                "\",serial_no=\"" + certSerialNo + "\",signature=\"" + signature + "\"";
    }

    /**
     * 微信支付-前端唤起支付参数-获取商户私钥
     *
     * @param filename 私钥文件路径  (required)
     * @return 私钥对象
     */
    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.decodeBase64(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");
        }
    }

    public static String getRandomString(int length) {
        String base = "abcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        return sb.toString();
    }

常见错误

接口返回没有开通API支付之类的话，是因为微信商户平台没有打开API转账权限
开通方法：产品中心-商家转账到零钱-前往功能，已开通如下图所示

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