Re: A query on the classloader architecture

[Archie Cobbs]

Chris Gray wrote:
> During bootstrapping, a native code (C) classloader is used to load the most 
> fundamental classes; Object, Class, String, Thread, etc.. This classloader 
> only searches one file, namely the first .jar or .zip in the bootstrap 
> classpath (normally this is wre.jar). As soon as it is possible to run Java 
> bytecode a Java bootstrap classloader is created, and this classloader 
> inherits all classes loaded by the native code. The Java bootstrap class 
> loader will load classes and system resources from the whole bootstrap class 
> path (-Xbootclasspath). All requests to load a class in java.* or wonka.* are 
> dispatched to the system class loader, by-passing the class loader hierarchy.
> 
> Classes which are loaded by the Java bootstrap classloader will return a 
> reference to the Java bootstrap classloader as class.getClassLoader(). 
> Classes which are loaded by the native code classloader will return null 
> (this could change), as will primitive data types. We have not seen any 
> problems resulting from this, but some code written to a Java 1.1 security 
> model could fail if it assumes classloader null <=> system class.
> 
> The extension class loader is created only if java.ext.dirs.path exists. It 
> loads classes from this path, and its parent is the (Java) bootstrap class 
> loader.
> 
> The application class loader loads classes from -classpath/$CLASSPATH, and is 
> responsible for loading the application specified on the command line. Its 
> parent is the extension class loader if this exists, the (Java) bootstrap 
> class loader otherwise.

So.. (I hope this doesn't sound like an annoying question) what is the
point of creating your "Java bootstrap classloader" ? Why not just let
your primoridal native code class loader fill this role as well? Is all
you're trying to do is prevent getClassLoader() from ever returning null?

If so, a separate question which underlies this whole discussion is
is whether that goal is worthwhile or not.. guess the jury's still out.

Thanks,
-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com