获取微信平台证书(保存)

平台证书微信平台是没有提供的，需要我们自个获取

需要准备的东西如下：

商户号、apiclient_key.pem(下载证书的时候有提供)、api秘钥

依赖

<!-- alipay-->
        <dependency>
            <groupId>com.alipay.sdk</groupId>
            <artifactId>alipay-sdk-java</artifactId>
            <!--<version>3.7.26.ALL</version>-->
        </dependency>

下面开始上代码

/**
     * 获取平台证书
     *
     * @return
     */
    @Override
    public Map<String, Object> getPlatformCertificate() {
        // 获取平台证书列表
        try {
            IJPayHttpResponse response = WxPayApi.v3(
                    RequestMethod.GET,
                    WxDomain.CHINA.toString(),
                    WxApiType.GET_CERTIFICATES.toString(),
                    WxPayConfig.MCH_ID,
                    getSerialNumber(),
                    null,
                    WxPayConfig.keyPath,
                    ""
            );

            //String timestamp = response.getHeader("Wechatpay-Timestamp");
            //String nonceStr = response.getHeader("Wechatpay-Nonce");
            String serialNumber = response.getHeader("Wechatpay-Serial");
            //String signature = response.getHeader("Wechatpay-Signature");
            String body = response.getBody();
            int status = response.getStatus();

            log.info("serialNumber: {}", serialNumber);
            log.info("status: {}", status);
            log.info("body: {}", body);
            int isOk = 200;
            if (status == isOk) {
                cn.hutool.json.JSONObject jsonObject = JSONUtil.parseObj(body);
                JSONArray dataArray = jsonObject.getJSONArray("data");
                // 默认认为只有一个平台证书
                cn.hutool.json.JSONObject encryptObject = dataArray.getJSONObject(0);
                JSONObject encryptCertificate = encryptObject.getJSONObject("encrypt_certificate");
                String associatedData = encryptCertificate.getStr("associated_data");
                String cipherText = encryptCertificate.getStr("ciphertext");
                String nonce = encryptCertificate.getStr("nonce");
                String serialNo = encryptObject.getStr("serial_no");
                //平台证书文件要存在，即使是空的
                String platSerialNo = savePlatformCert(associatedData, nonce, cipherText, WxPayConfig.platformCertPath);
                log.info("平台证书序列号: {} serialNo: {}", platSerialNo, serialNo);
            }
            // 根据证书序列号查询对应的证书来验证签名结果
            boolean verifySignature = WxPayKit.verifySignature(response, WxPayConfig.platformCertPath);
            System.out.println("verifySignature:" + verifySignature);
            Map<String, Object> maps = (Map<String, Object>) JSON.parse(body);
            return maps;
        } catch (Exception e) {
            e.printStackTrace();
            throw new CustomException("系统繁忙，请稍后重试");
        }
    }

/**
     * 保存平台证书
     *
     * @param associatedData 关联数据
     * @param nonce          随机字符串
     * @param cipherText     密文
     * @param certPath       证书路径
     * @return
     */
    private String savePlatformCert(String associatedData, String nonce, String cipherText, String certPath) {
        try {
            AesUtil aesUtil = new AesUtil(WxPayConfig.API_SECRET.getBytes(StandardCharsets.UTF_8));
            // 平台证书密文解密
            // encrypt_certificate 中的  associated_data nonce  ciphertext
            String publicKey = aesUtil.decryptToString(associatedData.getBytes(StandardCharsets.UTF_8), nonce.getBytes(StandardCharsets.UTF_8), cipherText);
            // 保存证书
            FileWriter writer = new FileWriter(certPath);
            writer.write(publicKey);
            // 获取平台证书序列号
            X509Certificate certificate = PayKit.getCertificate(new ByteArrayInputStream(publicKey.getBytes()));
            return certificate.getSerialNumber().toString(16).toUpperCase();
        } catch (Exception e) {
            e.printStackTrace();
            return e.getMessage();
        }
    }

/**
     * 平台证书 格式.pem 这里需要用绝对路径
     */
    public static final String platformCertPath = "classpath:cert/platformCert.pem";

执行后平台证书就下载到target目录下了

-----BEGIN PUBLIC KEY-----
-----END PUBLIC KEY-----