kotlin okhttp3怎么自动从https网站保存cer证书到本地 给出示例代码

你可以使用OkHttp的CertificatePinner类来验证证书，然后使用OkHttp的SSLContext来保存证书。以下是示例代码：

// 创建OkHttpClient
OkHttpClient client = new OkHttpClient.Builder()
        .certificatePinner(new CertificatePinner.Builder()
                .add("example.com", "sha256/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=")
                .build())
        .build();

// 获取证书
CertificatePinner certificatePinner = client.certificatePinner();
Set<String> pins = certificatePinner.pins("example.com");

// 保存证书
SSLContext sslContext = SSLContext.getInstance("TLS");
KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
keyStore.load(null, null);
for (String pin : pins) {
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    InputStream inputStream = new ByteArrayInputStream(Base64.decode(pin.split("/")[1], Base64.DEFAULT));
    X509Certificate cert = (X509Certificate) cf.generateCertificate(inputStream);
    keyStore.setCertificateEntry(cert.getSubjectDN().toString(), cert);
}
TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
trustManagerFactory.init(keyStore);
sslContext.init(null, trustManagerFactory.getTrustManagers(), null);

// 创建OkHttpClient
OkHttpClient newClient = client.newBuilder()
        .sslSocketFactory(sslContext.getSocketFactory(), (X509TrustManager) trustManagerFactory.getTrustManagers()[])
        .build();

注意：这里的证书是使用Base64编码的，你需要将证书的内容替换成你自己的证书内容。