新接入商户号，配置后提示错误《下载平台证书返回状态码异常，状态码为:500》，查了下之前有人反馈《新商户不再签发平台证书，需要使用商户公钥进行敏感信息加密和验签》，这个商户公钥是通过 https://pay.weixin.qq.com/doc/v3/merchant/4012153196 这里获取的吗，但是下载的文件pub_key.pem 在加载的时候提示错误，《无效的证书》， 《Unable to initialize, java.io.IOException: Too short》，加载的代码如下 使用的是 https://github.com/wechatpay-apiv3/wechatpay-apache-httpclient
得如何加载和使用这个公钥呢
X509Certificate publicKey = PemUtil.loadCertificate(new ClassPathResource(merchantId + "/pub_key.pem").getInputStream());
Verifier verifier = new CertificatesVerifier(Collections.singletonList(publicKey));
新接入的商户号使用公钥可参考：https://pay.weixin.qq.com/docs/merchant/products/platform-certificate/wxp-pub-key-guide.html
https://github.com/wechatpay-apiv3/wechatpay-java
用https://search.maven.org/artifact/com.github.wechatpay-apiv3/wechatpay-java
// 可以根据实际情况使用publicKeyFromPath或publicKey加载公钥 Config config = new RSAPublicKeyConfig.Builder() .merchantId(merchantId) .privateKeyFromPath(privateKeyPath) .publicKeyFromPath(publicKeyPath) .publicKeyId(publicKeyId) .merchantSerialNumber(merchantSerialNumber) .apiV3Key(apiV3Key) .build();// 这是以前的使用方式ClassPathResource classPathResource = new ClassPathResource(MerchantConfig.getV3KeyPath(merchantId));PrivateKey privateKey = PemUtil.loadPrivateKey(classPathResource.getInputStream());// 获取证书管理器实例CertificatesManager certificatesManager = CertificatesManager.getInstance();// 向证书管理器增加需要自动更新平台证书的商户信息certificatesManager.putMerchant(merchantId,new WechatPay2Credentials(merchantId, new PrivateKeySigner(merchantConfig.getSerialNumber(), privateKey)),merchantConfig.getApiV3Key().getBytes(StandardCharsets.UTF_8));// ... 若有多个商户号，可继续调用putMerchant添加商户信息// 从证书管理器中获取verifierVerifier verifier = certificatesManager.getVerifier(merchantId);CloseableHttpClient builder = WechatPayHttpClientBuilder.create().withMerchant(merchantId, merchantConfig.getSerialNumber(), privateKey).withValidator(new WechatPay2Validator(verifier)).build();WxpayFeignService wxpayFeignService = Feign.builder().client(new ApacheHttpClient(builder)).encoder(new SpringEncoder(messageConverters())).decoder(new SpringDecoder(messageConverters())).requestInterceptor(template -> template.header("Content-Type", "application/json; charset=utf-8")).logLevel(loggerLevel).logger(new Slf4jLogger(WxpayFeignService.class)).contract(new SpringMvcContract()).target(WxpayFeignService.class, "https://api.mch.weixin.qq.com");PublicKey publicKey = PemUtil.loadCertificate(new ClassPathResource(merchantId + "/pub_key.pem").getInputStream());Verifier verifier = new CertificatesVerifier(Collections.singletonList(publicKey));.withMerchant(merchantId, merchantConfig.getSerialNumber(), privateKey)