Re: Java/OO techniques for modularity and re-use

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 01 Jul 2007 18:11:06 -0400

Message-ID:

<4688267b$0$90265$14726298@news.sunsite.dk>

Richard Maher wrote:

Since SSLSocket inherits from Socket then you can make your
t3sock of type Socket (you can assign from a subtype to a
super type).

But because SSLSocket "extends" Socket, surely I have to instantiate a
SSLSocket object somewhere don't I?

Really no need for this: -
sockFactory = (SSLSocketFactory)SSLSocketFactory.getDefault();
t3Sock = (SSLSocket)sockFactory.createSocket();

What about all the Value-Added SSL bits that the SSLSocket class must
bolt-on to a Socket?

If you need to use a SSL specific funtion you can use:
((SSLSocket)t3Sock).someSSLSOcketSpecificMethod()

You're casting t3Sock (a Socket object) as a SSLSocket object there right? I
haven't missed some abstract-class or Interface wizardry? So I've got a
vanilla Socket and cast it as a SSLSocket to call, say startHandshake(), and
it's not gonna complain about a bodgy brick-veneer job, absent any
certificate or crypto-algorithm info?

I'd find it easier to picture it the other way around where we have a
SSLSocket and our casting it as a Socket effectively masks out all the SSL
bits, but who cares? I'll just code it like you've said and see how I get
on.

Below are a little standalone console app client-server example.

I know you are in applet environment, but the idea is general.

Look for the hack section.

Arne

============================================================

import java.io.*;
import java.net.*;

import javax.net.ssl.*;

public class MultiServer {
     private final static int PORT = 12345;
     public static void main(String[] args) throws Exception {
         ServerSocket ss;
         if(args.length > 0 && args[0].equals("SSL")) {
             System.out.println("SSL");
             ss =
SSLServerSocketFactory.getDefault().createServerSocket(PORT);
         } else {
             System.out.println("Non-SSL");
             ss = new ServerSocket(PORT);
         }
         System.out.println("Accepting connection");
         Socket s = ss.accept();
         System.out.println("Reading");
         InputStream is = s.getInputStream();
         byte[] b = new byte[10000];
         int blen = 0;
         int n;
         while((n = is.read(b, blen, b.length - blen)) > 0) {
             blen += n;
         }
         System.out.print("Received " + blen + " bytes from client:");
         for(int i = 0; i < blen; i++) System.out.print(" " + b[i]);
         System.out.println();
         System.out.println("Closing");
         is.close();
         s.close();
         ss.close();
    }
}

import java.io.*;
import java.net.*;
import java.security.*;
import java.security.cert.*;

import javax.net.ssl.*;

public class MultiClient {
     private final static String HOST = "localhost";
     private final static int PORT = 12345;
     public static void main(String[] args) throws Exception {
         Socket s;
         if(args.length > 0 && args[0].equals("SSL")) {
             System.out.println("Connecting via SSL");
             SSLContext sslctx = SSLContext.getInstance("SSL");
             sslctx.init(null, new X509TrustManager[] { new
MyTrustManager() }, null);
             SSLSocketFactory sf = sslctx.getSocketFactory();
             s = sf.createSocket(new Socket(HOST, PORT), HOST, PORT, true);
         } else {
             System.out.println("Connecting plain");
             s = new Socket(HOST, PORT);
         }
         // hack
         if(s instanceof SSLSocket) {
             SSLSession ses = ((SSLSocket)s).getSession();
             System.out.println("Server: " + ses.getPeerPrincipal());
         }
         System.out.println("Sending 1 2 3 to server");
         OutputStream os = s.getOutputStream();
         byte[] b = { 1, 2, 3 };
         os.write(b);
         System.out.println("Closing");
         os.close();
         s.close();
    }
}

class MyTrustManager implements X509TrustManager
{
     public void checkClientTrusted(X509Certificate[] chain, String
authType) {
     }
     public void checkServerTrusted(X509Certificate[] chain, String
authType) {
     }
     public X509Certificate[] getAcceptedIssuers() {
         return new X509Certificate[0];
     }
}

C:\>java MultiServer
Non-SSL
Accepting connection
Reading
Received 3 bytes from client: 1 2 3
Closing

C:\>java -Djavax.net.ssl.keyStore=server.jks
-Djavax.net.ssl.keyStorePassword=superhemmeligt MultiServer SSL
SSL
Accepting connection
Reading
Received 3 bytes from client: 1 2 3
Closing

C:\>java MultiClient
Connecting plain
Sending 1 2 3 to server
Closing

C:\>java MultiClient SSL
Connecting via SSL
Server: CN=Unknown, OU=Unknown, O=Unknown, L=Unknown, ST=Unknown, C=Unknown
Sending 1 2 3 to server
Closing

Arne