登录https网站并仅使用核心Java API下载页面

我想使用用户名和密码登录到https网站，转到该网站的一个网址，然后在网址下载页面（也许可以解析该网页的内容） . 我想使用核心Java apis而不是htmlunit，jsoup等来做这个 . 我得到了下面的代码来学习如何做到这一点，但它没有告诉我如何登录到网站 . 请告诉我如何登录，维护会话，然后最终关闭连接 .

来源 - http://www.mkyong.com/java/java-https-client-httpsurlconnection-example/

import java.net.MalformedURLException;
import java.net.URL;
import java.security.cert.Certificate;
import java.io.*;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLPeerUnverifiedException;

public class HttpsClient{

   public static void main(String[] args)
   {
        new HttpsClient().testIt();
   }

   private void testIt(){

      String https_url = "https://www.google.com/";
      URL url;
      try {

         url = new URL(https_url);
         HttpsURLConnection con = (HttpsURLConnection)url.openConnection();

         //dumpl all cert info
         print_https_cert(con);

         //dump all the content
         print_content(con);

      } catch (MalformedURLException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }

   }

   private void print_https_cert(HttpsURLConnection con){

    if(con!=null){

      try {

    System.out.println("Response Code : " + con.getResponseCode());
    System.out.println("Cipher Suite : " + con.getCipherSuite());
    System.out.println("\n");

    Certificate[] certs = con.getServerCertificates();
    for(Certificate cert : certs){
       System.out.println("Cert Type : " + cert.getType());
       System.out.println("Cert Hash Code : " + cert.hashCode());
       System.out.println("Cert Public Key Algorithm : " 
                                    + cert.getPublicKey().getAlgorithm());
       System.out.println("Cert Public Key Format : " 
                                    + cert.getPublicKey().getFormat());
       System.out.println("\n");
    }

    } catch (SSLPeerUnverifiedException e) {
        e.printStackTrace();
    } catch (IOException e){
        e.printStackTrace();
    }

     }

   }

   private void print_content(HttpsURLConnection con){
    if(con!=null){

    try {

       System.out.println("****** Content of the URL ********");            
       BufferedReader br = 
        new BufferedReader(
            new InputStreamReader(con.getInputStream()));

       String input;

       while ((input = br.readLine()) != null){
          System.out.println(input);
       }
       br.close();

    } catch (IOException e) {
       e.printStackTrace();
    }

       }

   }

}