Re: [groovy-user] RootLoader for system class?

begin Jochen Theodorou quotation:
> Even if the system class loader did respond to loading a class we cannot 
> know if the loaded class is a system class or or for example simply in 
> the endorsed directory or whatever. A simple example si the usage of 
> commons-cli. We depend here on a certain version and there are other 
> versions around. If now such a version somehow shows up in the system 
> loader Groovy would probably not even start from command line anymore.

Why would Groovy not start? If it's the wrong version of the library?
People could stick the Groovy JAR in the endorsed directory too and it
would also cause problems. I'm not sure why Groovy should be violating
the ClassLoader contract here because someone might put something weird
into the endorsed directory if it has the side effect of loading JDK
classes from the wrong classloader.

> If that wouldn't be needed RootLoader would not be needed too and it 
> could be a normal URLClassLoader instead... maybe not even that.
> 
> Of course this can have other side effects as well... for example APIs 
> that are "suddenly" included in the jdk and where not before, but we did 
> need them. You have this for MX, for XML and for other things probably 
> too. And who knows what the future will bring here

Well perhaps something like the way servlet containers handle this
should be considered since they are also child-first. My understanding
is that they generally have a way of switching to parent-first mode for
certain packages (e.g. "java.*" and "javax.*").

If the current classloader situation is going to be maintained, it seems
like pieces of code that depend on known libraries that have been
integrated into some JDK version some be packaged in a separate module
with JDK-specific versions. It seems from the SVN history that this was
not the case with MBeanServerConnection at the time GroovyMBean was
created, but it would have been great if this had been fixed at some
time in the last four years since Java 5 has been out. I'm glad to hear
from Paul that this particular case has been addressed for Groovy 1.6.

-md

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