HTTPS主要用于安全传输数据，从代码的角度来看，HTTPS主要使用了X509的方式进行了加密，至于密钥(证书)在什么地方，可能在购买HTTPS服务的时候被统一放置在DNS服务器之类的地方了吧(纯推测)：

package com.sahadev;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.URL;
import java.security.SecureRandom;
import java.security.cert.X509Certificate;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.KeyManager;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.X509TrustManager;

import org.apache.http.conn.ssl.AllowAllHostnameVerifier;


public class HttpClient {
	private static final AllowAllHostnameVerifier HOSTNAME_VERIFIER = new AllowAllHostnameVerifier();
	private static X509TrustManager xtm = new X509TrustManager() {
		public void checkClientTrusted(X509Certificate[] chain, String authType) {
		}

		public void checkServerTrusted(X509Certificate[] chain, String authType) {
		}

		public X509Certificate[] getAcceptedIssuers() {
			return null;
		}
	};
	private static X509TrustManager[] xtmArray = new X509TrustManager[] { xtm };
	private static HttpsURLConnection conn = null;


	public static String sendHttpsPost(String path, String params) throws Exception {
		// 组拼实体数据
		byte[] entity = params.getBytes("UTF-8");
		URL url = new URL(path);
		conn = (HttpsURLConnection) url.openConnection();
		if (conn instanceof HttpsURLConnection) {
			// Trust all certificates
			SSLContext context = SSLContext.getInstance("TLS");
			context.init(new KeyManager[0], xtmArray, new SecureRandom());
			SSLSocketFactory socketFactory = context.getSocketFactory();
			((HttpsURLConnection) conn).setSSLSocketFactory(socketFactory);
			((HttpsURLConnection) conn).setHostnameVerifier(HOSTNAME_VERIFIER);
		}
		conn.setConnectTimeout(5 * 1000);
		conn.setReadTimeout(30000);
		conn.setDoInput(true);
		conn.setDoOutput(true);// 允许输出数据
		conn.setUseCaches(false);
		conn.setRequestMethod("POST");
		conn.setRequestProperty("Content-Type", "application/json");
		conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows; U; Windows NT 6.1; zh-CN; rv:1.9.2.6)");

		OutputStream outStream = new DataOutputStream(conn.getOutputStream());
		outStream.write(entity);
		
		outStream.flush();
		outStream.close();

		BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
		StringBuffer sb = new StringBuffer();
		String line;
		while ((line = br.readLine()) != null) {
			sb.append(line);
		}

		return sb.toString();
	}

	public static void closeConnection() {
		if (conn != null)
			conn.disconnect();
	}
}