May 1998
Intermediate to advanced
362 pages
10h 8m
English
Content preview from Java Cryptography
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Renegade
For all three browsers, we’ll use
the same applet, called Renegade.
Renegade isn’t really dangerous, but it does
try to find out your name, using
System.getProperty("user.name").
This action is not allowed in the applet sandbox, to protect the
privacy of the user. In Renegade, we enclose this
call in a try block in case a
SecurityException is thrown. Save the source code for this class in
Renegade.java.
import java.applet.*;
import java.awt.*;
public class Renegade extends Applet {
private String mMessage;
public void init() {
try {
mMessage = "Your name is " + System.getProperty("user.name") + ".";
}
catch (SecurityException e) {
mMessage = "Can't get your name, due to a SecurityException.";
}
}
public void paint(Graphics g) {
g.drawString("Renegade", 25, 25);
g.drawString(mMessage, 25, 50);
}
}The HTML page that contains this applet, Renegade.html, is as follows:
<html> <head> </head> <body> <applet code = Renegade width = 300 height = 200></applet> </body> </html>
If you point your browser at this applet, the call to
System.getProperty() fails, just as we expected.
Figure 8.1 shows this applet in Navigator 4.01.
 |
Figure 8-1. The unsigned Renegade applet can’t get out of the sandbox
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.