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Groups > comp.lang.java.programmer > #29500

Re: dealing with ClassLoaders...

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Martin Gregorie <martin@address-in-sig.invalid> wrote:
> On Fri, 01 Aug 2014 21:10:07 +0000, Andreas Leitgeb wrote:
>> Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> wrote:
>>> Martin Gregorie <martin@address-in-sig.invalid> wrote:
>>>> public class MAClassLoader extends ClassLoader {
>>>   [ no snip ]
>>>> }
>>>> I hope this is useful info.
>> On further examination, I think it isn't as simple as that. Essentially,
>> this "empty" ClassLoader-subclass would pass everything through to the
>> parent classloader (or the pre-mordial one, absent a parent) and thus
>> not be associated to any of the classes loaded through it, thus provide no
>> isolation at all.
> Your requirements would seem to be as bit different from mine, which were 
> purely to package a number of programs (some Swing apps, some pure 
> command-line apps, all accessing a single PostgreSQL database instance) 
> into one convenient file and to be able to run them without needing to 
> unpack the distribution file.

That's the point. In your case there was no need for isolation, and
there wasn't really a point in creating this MAClassLoader at all.
Merely loading the starting class could have been done with Class.forName()
thus without any custom classloader. Essentially, what I had before the
requirement for multiple apps per VM came up.

I still appreciate that you posted it: That I got so far as to understand
what MAClassLoader does, was an important first learning step for me.

> Once the top level class defining the program to 
> be run has been loaded I don't care what class loader is used to pull in 
> the other classes it needs - in fact I'd be surprised if the default 
> class loader *wasn't* used for that.  

The default classloader *was* used for the other classes (no surprise so far),
but it was also used for that one dynamic starting class (which didn't matter
in your case, but may still be a theoretic surprise now in hindsight).

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Thread

dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-07-31 19:40 +0000
  Re: dealing with ClassLoaders... Martin Gregorie <martin@address-in-sig.invalid> - 2014-07-31 20:44 +0000
    Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-01 14:22 +0000
      Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-01 21:10 +0000
        Re: dealing with ClassLoaders... Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-08-01 17:32 -0400
          Re: dealing with ClassLoaders... Joerg Meier <joergmmeier@arcor.de> - 2014-08-02 01:21 +0200
          Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-02 00:00 +0000
        Re: dealing with ClassLoaders... Martin Gregorie <martin@address-in-sig.invalid> - 2014-08-01 21:45 +0000
          Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-01 23:14 +0000
            Re: dealing with ClassLoaders... Martin Gregorie <martin@address-in-sig.invalid> - 2014-08-02 00:35 +0000
              Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-05 15:38 +0000
  Re: dealing with ClassLoaders... Silvio <silvio@internet.com> - 2014-08-01 13:31 +0200
    Re: dealing with ClassLoaders... Silvio <silvio@internet.com> - 2014-08-01 13:37 +0200
      Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-01 16:06 +0000
  Re: dealing with ClassLoaders... "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2014-08-01 13:19 +0100
    Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-01 15:51 +0000
  Re: dealing with ClassLoaders... Josip Almasi <joe@vrspace.org> - 2014-08-01 15:55 +0200
    Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-04 15:12 +0000
      Re: dealing with ClassLoaders... Mike Amling <mamling@chaff.us> - 2014-08-04 19:53 -0500
        Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-05 15:16 +0000
      Re: dealing with ClassLoaders... Josip Almasi <joe@vrspace.org> - 2014-08-08 11:53 +0200
        Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-08 18:46 +0000
          Re: dealing with ClassLoaders... Josip Almasi <joe@vrspace.org> - 2014-08-10 13:22 +0200
            Re: dealing with ClassLoaders... Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-08-12 17:16 +0000

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