SystemClassLoader

[Robert Lougher]

Hi,

I've been a long time lurker on this mailing list, but I've got a 
question I hope the classpath developers can answer...

I'm the developer of yet another open-source Java VM 
(http://jamvm.sourceforge.net).  I'm about to release version 1.1.1 
which has been updated to Classpath-0.07 (basically VMThread/Thread).

One of the things I've finally got round to changing is using a system 
class loader to load application classes (up to now loaded via the 
bootstrap - I've been more interested in getting the Reflection API 
fully implemented).

Looking at the code, the "default" system class loader (in 
gnu.java.lang...) simply delegates to the bootstrap loader - it doesn't 
implement findClass.  Obviously, it's not difficult to write my own to 
parse and search the classpath (zip, jar, file...).  However, is there 
any reason why I can't simply sub-class URLClassLoader, and construct a 
list of URLs?  I've got a simple SystemClassLoader based on 
URLClassLoader and it seems to work OK.

Performance-wise, the VM keeps it's own list of loaded-classes so a 
class-loader isn't continually asked for the same class (although this 
will work).   Note, I'm interested in doing this so that JamVM can read 
from jar and zip files - implementing zip in the VM duplicates 
functionality and I'm trying to keep JamVM small (approx 80K on Intel, 
100K on PowerPC stripped).

Thanks,

Rob.

P.S.  Thank you for your work on Classpath - I've been using it since 
0.04 and it's come a long way.  With Classpath-0.06 I was able to run 
Jetty-4.2.14 (web server and servlet container) on a 50MHz PowerPC with 
only a couple of modifications, which have been fixed in 0.07...