參考連結：

https://stackoverflow.com/questions/12501117/programmatically-obtain-keystore-from-pem

https://stackoverflow.com/questions/6559272/algid-parse-error-not-a-sequence

https://stackoverflow.com/questions/15344125/load-a-rsa-private-key-in-java-algid-parse-error-not-a-sequence/21458628

http://www.bouncycastle.org/latest_releases.html

生成SSLSocketFactory程式碼（核心）：

import javax.net.ssl.KeyManager;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.xml.bind.DatatypeConverter;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.nio.file.Files;
 
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.KeyStore;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
 
import java.security.interfaces.RSAPrivateKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;

public class KeyTest {

  public static SSLSocketFactory getSocketFactoryPEM(String certPath, String keyPath) throws Exception {
    byte[] certByte = Files.readAllBytes(Paths.get(certPath));
    byte[] keyByte = Files.readAllBytes(Paths.get(keyPath));

    byte[] certBytes = parseDERFromPEM(certByte, "-----BEGIN CERTIFICATE-----", "-----END CERTIFICATE-----");
    byte[] keyBytes = parseDERFromPEM(keyByte, "-----BEGIN RSA PRIVATE KEY-----", "-----END RSA PRIVATE KEY-----");

    X509Certificate cert = generateCertificateFromDER(certBytes);
    RSAPrivateKey key  = generatePrivateKeyFromDER(keyBytes);

    KeyStore keystore = KeyStore.getInstance("JKS");
    keystore.load(null);
    keystore.setCertificateEntry("cert-alias", cert);
    keystore.setKeyEntry("key-alias", key, "<password>".toCharArray(), new Certificate[] {cert});

    KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
    kmf.init(keystore, "<password>".toCharArray());

    KeyManager[] km = kmf.getKeyManagers();

    SSLContext context = SSLContext.getInstance("TLS");
    context.init(km, null, null);

    return context.getSocketFactory();
  }

  private static byte[] parseDERFromPEM(byte[] pem, String beginDelimiter, String endDelimiter) {
    String data = new String(pem);
    String[] tokens = data.split(beginDelimiter);
    tokens = tokens[1].split(endDelimiter);
    return DatatypeConverter.parseBase64Binary(tokens[0]);
  }

  private static RSAPrivateKey generatePrivateKeyFromDER(byte[] keyBytes) throws InvalidKeySpecException, NoSuchAlgorithmException {
    java.security.Security.addProvider(
      new org.bouncycastle.jce.provider.BouncyCastleProvider()
    );
    PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory factory = KeyFactory.getInstance("RSA");
    return (RSAPrivateKey)factory.generatePrivate(spec);
  }

  private static X509Certificate generateCertificateFromDER(byte[] certBytes) throws CertificateException {
    CertificateFactory factory = CertificateFactory.getInstance("X.509");
    return (X509Certificate)factory.generateCertificate(new ByteArrayInputStream(certBytes));
  }

}

後續https請求程式碼：

okhttp：

private void test()throws Exception {
    JSONObject jsonObject = new JSONObject();
    jsonObject.put("test", "123");
    OkHttpClient client = new OkHttpClient.Builder()
      .sslSocketFactory(KeyTest.getSocketFactoryPEM("",""))
      .build();
    Request request = new Request.Builder()
      .url("")
      .post(RequestBody.create(MediaType.parse("application/json"), jsonObject.toJSONString()))
      .build();

    client.newCall(request).enqueue(new Callback() {
      @Override
      public void onFailure(Call call, IOException e) {
        System.out.println("--------------onFailure--------------" + e.toString());
      }

      @Override
      public void onResponse(Call call, Response response) throws IOException {
        System.out.println("--------------onResponse--------------" + response.body().string());
      }
    });
  }