如何从PKCS12证书中解析私钥、公钥和证书序列号

public class P12Application {
    public static void main(String[] args) throws Exception {
        //从文件中解析
        try (FileInputStream is = new FileInputStream("apiclient.p12")) {
            System.out.println(P12Info.parse(is, "证书密码"));
        }

        //从Base64加密串中解析
        String p12Base64 = "xxxyyyzzz";
        byte[] base64byte = Base64.getDecoder().decode(p12Base64);
        try (ByteArrayInputStream is = new ByteArrayInputStream(base64byte)) {
            System.out.println(P12Info.parse(is, "证书密码"));
        }
    }

    @Data
    @Builder
    private static class P12Info {
        /**
         * 证书序列号.
         */
        private final String serialNo;

        /**
         * 证书秘钥.
         */
        private final PrivateKey privateKey;

        /**
         * 公钥.
         */
        private final PublicKey publicKey;

        public static P12Info parse(InputStream is, String passwd) throws Exception {
            KeyStore ks = KeyStore.getInstance("PKCS12");
            ks.load(is, passwd.toCharArray());
            String keyAlias = null; 
            //解析证书，必须有别名
            Enumeration<String> aliases = ks.aliases();
            if (aliases.hasMoreElements()) {
                keyAlias = aliases.nextElement();
            }
            //解析私钥
            PrivateKey privateKey = (PrivateKey) ks.getKey(keyAlias, passwd.toCharArray());
            Certificate cert = ks.getCertificate(keyAlias);
            BigInteger serialNumber = ((X509CertImpl) cert).getSerialNumber();
            //证书一般都使用16进制表示
            String certSn = serialNumber.toString(16);
           
            //设置证书序列号和私钥
            return P12Info.builder()
                    .serialNo(certSn)
                    .privateKey(privateKey)
                    .publicKey(cert.getPublicKey())
                    .build();
        }
    }
}