//核心 验签 verifier的构建
ScheduledUpdateCertificatesVerifier verifier = null;
try {
/**
* mchSerialNo 商户API证书序列号
* privateKey 商户私钥文件
* mchId 商户号
* signer 签名
* apiV3Key APIv3密钥
*/
PrivateKeySigner signer = new PrivateKeySigner(mchSerialNo, privateKey);
WechatPay2Credentials credentials = new WechatPay2Credentials(mchId, signer);
byte[] bytes = apiV3Key.getBytes("utf-8");
verifier = new ScheduledUpdateCertificatesVerifier(credentials, bytes);
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e);
}