Re: Help with classloader and NullPointerException

From:
Casper Bang <casper@jbr.dk>
Newsgroups:
comp.lang.java.help
Date:
Sun, 25 Nov 2007 02:03:07 +0100
Message-ID:
<4748c9f6$0$15893$edfadb0f@dtext01.news.tele.dk>
Ah my own bad, apparently some SwingX library code requires
UIManager.setLookAndFeel to have been called.

/Casper

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(Class.java:169) 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()
    {
        super(CustomClassLoader.class.getClassLoader());
    }
}

Any pointers greatly appreciated.

/Casper

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