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Message:

Visibility across classloaders?

Posted by Wayne Stidolph on July 04, 2000 at 10:30 PM

I am wondering about good design approaches to "exporting" an
interface from one classloader into another, all in the same JVM.

Suppose I want to have a Class "A_impl" which implements
interface "A" and a class B that uses an A_impl object found
in a JNDI namespace. The ideal code in B is something like:

A myA = (A)context.lookup("theObj");

Is there a way tomake this work if A and A_impl are defined by
user Classloader "ACL" and B is defined by user Classloader BCL,
and there is no parent-child relationship between ACL and BCL?

The problem is that the code in B uses BCL, so using "A" fails.
Adding A.class to be loaded by BCL as well as ACL doesn't work;
gets an invalid class cast exception (I think the object "theObj"
hold the reference backs to its defining classloader and the cast
is to an A defined under BCL, so they don't match, right?)

Is there a way to mark BCL as an "initiating" Classloader to get
access to the ACL "A" interface - and to do this for *only* the
"A" interface, not to any other information?

Clearly a parent can be inserted above ACL and BCL to share "A"
but this has a lot of other drawbacks for what I'm trying to do.
Any other ideas on creating sibling partial-exposure
relationships between Classloaders?

Wayne