How to extend a Java class with a loaded class?

I am injecting a Applet that way that 开发者_如何学Pythonit can't check on which website it is.

The purpose is to load an external unmodified applet into mine so I can embed it into mine.

    final URL[] appletURL = { new URL(Main.getBase() + "/loader.jar") };
    final URLClassLoader classLoader = new URLClassLoader(appletURL); // gets the class
    final Class<?> loader = classLoader.loadClass("loader"); // loads the class
    applet = (Applet) loader.newInstance(); // creates the applet
    applet.setStub(new Injector()); // injects the getdocumentbase, so it thinks he is on his own website
    applet.init(); // start applet
    applet.start();
    applet.setPreferredSize(new Dimension(800, 600)); // to be able to add to jframe properly

The "applet.setStub(new Injector());" part is to prevent navigating away or not loading because it's not the applet's own website.

But now I want to render the external applet to a screenshot. I tried this:

@Override
public void actionPerformed(final ActionEvent e) {
    final String s = e.getActionCommand();
    if (s.equals("Screenshot")) {
        final BufferedImage offScreen = new BufferedImage(800, 600, BufferedImage.TYPE_INT_RGB);
        applet.update(offScreen.createGraphics());
        try {
            ImageIO.write(offScreen, "PNG", new File("C:/Users/Mitchell/Pictures/screenshot.png"));
        } catch (Exception ex) {  }
    }
}

But it doesn't use the paint nor updat method. It uses getGraphics() instead, I got tipped to extend the applet that I want to screenshot. But the applet is dynamically loaded, so how do I extend a class with a loaded class (or applet)?

Can someone provide a code sample? I am about to freak out because this is taking all my time and I can't continue without this.

Take a look at cglib.

If instead of a class you want to extend, you want to implement an interface, take a look at java.lang.reflect.Proxy.

If you just add a field dynamically or otherwise, there won't be any code which uses it which is rather pointless,(except for access via reflection)

If you want a object with dynamic field names, perhaps a Map<String, Object> is what you really want.

You can extends a class which has an additional fields any number of ways provided its not final.

You can do this at compile time, you can compile code at runtime, you can add a class from generated byte code at runtime.

If you know you need to extend a class, write the code to do that and you don't need to generate anything.