[bug?] Dynamically defined classes cause linkage errors (duplicate definitions).

(Apologies if this has been discussed before and I missed it)

Hi Pat, everybody,

I've  just  encountered  an  unexpected  problem. Let me state the scenario
first, so that you know what I'm talking about:

I  have  a  method  that  executes  BeanShell scripts. Every script should,
theoretically,  be  given  its  own  namespace  (and  I'm  also giving it a
separate Interpreter object). Now, this script:

> import [...]
> 
> public class MyFactory implements LocalComponentFactory {
>     public LocalComponent getInstance() {
>             LocalComponent c = new StubOutputComponent();
>             c.setProperty("property", "value");
>             return c;
>     }
> };
> 
> return new LoadedComponentFactory(
>         /* id */ "stub-output", 
>         new MyFactory(), 
>         /* pool size */ 5);

which  defines  a  new  'scripted'  class  works  fine the first time it is
executed. But successive attempts to run it throw:

java.lang.LinkageError: duplicate class definition: MyFactory

I  looked  in  the source code and you always instantiate new classes using
BshClassManager's parent class loader:

>     public Class defineClass(String s, byte abyte0[])
>     {
>         ClassLoader classloader = getClass().getClassLoader();
>         Class class1;
>         try
>         {
>             class1 = (Class)Reflect.invokeObjectMethod(classloader, "defineClass", new Object[] {
>                 s, abyte0, new Primitive(0), new Primitive(abyte0.length)
>             }, (Interpreter)null, (CallStack)null, (SimpleNode)null);
>         }
...

This  approach  makes true script isolation virtually impossible, right? Or
am I missing something here.

Dawid

-- 
Dawid Weiss, http://www.cs.put.poznan.pl/dweiss
Laboratory of Intelligent Decision Support Systems, Poznan UT, Poland



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