Attila~
Thanks for the detailed response, that definitely clears the picture
up for me a lot.
Matt
On 10/5/07, Attila Szegedi <[EMAIL PROTECTED]> wrote:
>
> No can do. java.lang.ClassLoader has a field named "Vector classes"
> defined as:
>
> // The classes loaded by this class loader. The only purpose of this
> table
> // is to keep the classes from being GC'ed until the loader is GC'ed.
> private Vector classes = new Vector();
>
> It also has a method:
>
> void addClass(Class c) {
> classes.addElement(c);
> }
>
> that is invoked by *native* JVM code to add a class to the class loader
> when it is loaded. It being package-private method, it can't be overridden
> outside the package, and you also can't define a new class within
> java.lang.* package since it is sealed. Oh, and it is also pretty much
> specific to Sun JRE too :-)
>
> Mind you, it *might* be possible to do horrible hackery, like retrieving
> the "classes" field through reflection, with Field.setAccessible(false),
> and then clearing it from time to time. Needless to say, it would *not*
> work in any sane enterprise scenario when JVM runs under a security
> manager.
>
> The other way to get around this would be to run java with a tampered
> rt.jar in which ClassLoader.addClass() is modified to be a no-op.
>
> Again, all these solutions either require you to run without a security
> manager, or assume a Sun JRE, or both.
>
> However, also notice that the "classes" field is only used for the sole
> purpose of preventing GC of the class. I.e. it is not used by
> findLoadedClass, which actually delegates to native findLoadedClass0()
> method, hinting that there's further association of loaded class to its
> class loader somewhere in JVMs native guts. Meaning it might not be a good
> idea to try to pull the rug out of it, as it could well be assuming that
> the classes can't be GCed until the loader can be.
>
> You can say I gave some thought to this idea already :-)
>
> Attila.
>
> On Wed, 03 Oct 2007 16:15:04 +0200, Matt Fowles <[EMAIL PROTECTED]>
> wrote:
>
> >
> > All~
> >
> > Could you write your own class loader that uses PhatomReferences to
> > allow Classes to be GCed?
> >
> > Matt
> >
> > On 10/3/07, Charles Oliver Nutter <[EMAIL PROTECTED]> wrote:
> >>
> >> Attila Szegedi wrote:
> >> > Not referenced as in, unreachable? You use
> >> java.lang.ref.PhantomReference
> >> > for that.
> >>
> >> As in using Weak or Soft references to hold the classes; If some type of
> >> classloader had some kind of weak reference to the classes it contains,
> >> it would allow spinning up just the class rather than an entire
> >> garbage-collectable classloader to contain it (as is the case right now
> >> in JRuby).
> >>
> >> - Charlie
> >>
> >> >
> >>
> >
> > >
>
>
>
> --
> home: http://www.szegedi.org
> weblog: http://constc.blogspot.com
> Visit Szegedi Butterfly fractals at:
> http://www.szegedi.org/fractals/butterfly/index.html
>
> >
>
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