Accessing privileged methods in a Java Applet via JavaScript

I've been working on a Java applet that can get images from the user's clipboard or take screenshots of the user's desktop and upload them to a server via HTTP. The last piece of the puzzle was to make sure I could access the task methods via JavaScript, as the interface will most likely be driven by HTML.

I've been using a self-signed cert to sign the Java Applet so that I can access the user's clipboard and take the screenshot. All of this was tested and working extremely well from if I used the Applet UI. However, as soon as I would try to invoke one of the sandboxed functions from JavaScript the applet started throwing the error:

AccessControlException is thrown: access denied (java.awt.AWTPermission accessClipboard)

I tried a number of things to get around this problem. I thought it was something I was doing wrong when I was signing the applet (since it was working fine from within the Applet's built-in UI controls.) After playing around with the cert signing process and getting no where, I finally came across the post JavaScripting in Applets - Getting Out of the Sandbox where a comment from Stéphane Bury pointed me to a solution.

public static void doSpecialWork(String param1){
    final String fParam1 = param1;
    java.security.AccessController.doPrivileged(new java.security.PrivilegedAction() {
        public Object run() {
            // put the code of your method here
            ...
            ...
            return "";
        }
    });
}

My final solution was to write a command() method which I can use to trigger off the internal privileged methods:

/**
 * The method to invoke from JS to perform the privileged methods--which throw
 * security errors if you try to access them directly.
 *
 * @param command - the command you want to perform (clipboard, screenshot, upload)
 */
public void command(String command){
    final String cmd = command;

    java.security.AccessController.doPrivileged(
        new java.security.PrivilegedAction(){
            public Object run() {
                // execute the privileged command
                executeCommand(cmd);
                // we must return an object, so we'll return an empty string
                return "";
            }
        }
    );
}

As you can see the method is very basic, it just passes the command it received to a private method which actually executes the command. Now I can access any of the privileged methods in my applet with this little helper method.