Using openConnection() Method in java.net.URL Class

PKI Tutorials - Herong's Tutorial Examples

∟Java Programs Communicating with HTTPS Servers

∟Using openConnection() Method in java.net.URL Class

This section provides a tutorial example on how to use the openConnection() method in the java.net.URL class to perform a GET method on an HTTPS server. Java Secure Socket Extension (JSSE) works quietly behind the java.net.URL class to provide HTTPS support.

If you read the Java documentation on the openStream() method in the java.net.URL class, you will see that openStream() is actually a shorthand for openConnection().getInputStream(). In this tutorial, I want to write another test program to try openConnection() method following these steps:

Create a URL object with a URL string like "https://login.yahoo.com".
Generate a URLConnection object by calling the openConnection() method on the URL object.
Test the URLConnection object type: HttpURLConnection or HttpsURLConnection.
Get an InputStream object from the URLConnection object to read the response from the HTTPS server.

Here is the actual test program using the javax.net.ssl.HttpsURLConnection class to perform a GET command on an HTTPS server:

/* HttpsUrlConnection.java
 * Copyright (c) 2010-2018 HerongYang.com. All Rights Reserved.
 */
import java.io.*;
import java.net.URL;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import javax.net.ssl.HttpsURLConnection;
public class HttpsUrlConnection {
   public static void main(String[] args) {
      String sURL = args[0];
      try {
         URL oURL = new URL(sURL);
         URLConnection con = oURL.openConnection();

// Testing connection type
         if (con instanceof URLConnection)
            System.out.println("This is a URLConnection.");
         if (con instanceof HttpURLConnection)
            System.out.println("This is a HttpURLConnection.");
         if (con instanceof HttpsURLConnection)
            System.out.println("This is a HttpsURLConnection.");
         System.out.println("Connection object: "+con.toString());

// Reading data
         BufferedReader in = new BufferedReader(
            new InputStreamReader(con.getInputStream()));
         String line;
         while ((line = in.readLine()) != null)
            System.out.println(line);
         in.close();

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

Test 1: Run this test program to connect to https://login.yahoo.com:

herong> javac HttpsUrlConnection.java

herong> java HttpsUrlConnection https://login.yahoo.com

This is a URLConnection.
This is a HttpURLConnection.
This is a HttpsURLConnection.
Connection object:
   sun.net.www.protocol.https.DelegateHttpsURLConnection:
   https://login.yahoo.com

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3....
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Sign in to Yahoo!</title>

<meta http-equiv="Pragma" content="no-cache">
...

The test program is working! It confirms that https://login.yahoo.com is an HttpsURLConnection.

Test 2: Run this test program to connect to http://www.yahoo.com:

herong> java HttpsUrlConnection http://www.yahoo.com

This is a URLConnection.
This is a HttpURLConnection.
Connection object:
   sun.net.www.protocol.http.HttpURLConnection: http://www.yahoo.com

<!DOCTYPE html>
<html lang="en-US" class="y-fp-bg y-fp-pg-grad  bkt701">
<!-- m2 template 0 -->
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  <title>Yahoo!</title>
  <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
  <meta name="description" content="Welcome to Yahoo!, the world's ...