Re: alternative to my ClassLoader hack

Mark Space <>
Thu, 02 Apr 2009 10:34:36 -0700
<LA6Bl.15829$> wrote:

Based on that, I *think* I should use an URLClassLoader
however I've got no idea how to do this correctly.

I think you are correct. There's no way to do anything about the
security manager. If one is installed and denies you permissions, well
that's what it's supposed to do. The JVM itself is designed to be
"safe" and will allow the user to deny any program certain operations.
What you might want to think about is recovering gracefully from a
security exception. The easiest is just to pop up a dialog that says
"you need XXX permissions to run this app" then shut down.

For making your own URLClassLoader, just do it. Load your first class
with it, and invoke a method. Everthing afterthat will automatically
use the classloader it was invoked with, yours, and the URLClassLoader
automatically invokes it's parent to load classes it doesn't know about.

I haven't tried this, but I did look into it a while ago. Here's my
little sample:

package fubar;


public class MyClassLoader
     public static void main( String... args )
             throws ClassNotFoundException, InstantiationException,
         URL[] urls;
         urls = null; //... add some
         URLClassLoader cl = new URLClassLoader( urls );
         Class<MyClassLoader> main = (Class<MyClassLoader>) cl.
                 loadClass( "fubar.MyClassLoader" );
         MyClassLoader mcl = main.newInstance();

     private void startApplication()
         // everything else here

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