Re: Help with classloader and NullPointerException

Casper Bang <>
Sun, 25 Nov 2007 02:03:07 +0100
Ah my own bad, apparently some SwingX library code requires
UIManager.setLookAndFeel to have been called.


Casper Bang wrote:

I have an application which I would like to have the ability to restart
itself and thus flush all singletons, cached resources etc. I thought I
could do this by starting a new application instance dynamically with a
new custom classloader:

if(JOptionPane.showConfirmDialog(this.getMainFrame(), "Restart?",
"Restart?", JOptionPane.YES_NO_OPTION) == JOptionPane.YES_OPTION)
    ClassLoader classLoader = new CustomClassLoader();
    Class app = classLoader.loadClass("ActualApplication");
    Class[] classArray = { String[].class};
    Object[] stringArray = { new String[]{""}};
    Method method = app.getMethod("main", classArray);
    method.invoke(null, stringArray);

However, when my ActualApplication is invoked for the second time (when
trying to restart) I get NullPointerExceptions from various library
code, most noticably java.lang.Class.forName( where it
makes a call to ClassLoader.getCallerClassLoader().

I guess I am missing something here, what I don't understand is how come
its only at consecutive runs my application it fails. My
CustomClassLoader is simply:

public class CustomClassLoader extends ClassLoader
    public CustomClassLoader()

Any pointers greatly appreciated.


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