Problem: my J2EE ear file uses a third-party library (bunch of jar
files) to do SNMP stuff.  However, the J2EE vendor also uses this
third-party library to do its own SNMP stuff.  The problem is the vendor
uses a different version of the third-party library, so my code tries to
run and finds the wrong version of the library (of the jar files) that
the J2EE vendor has supplied.

Possible solution: I plan to have a custom classloader (derived from
java.lang.ClassLoader) that gets hooked in to my threads using
Thread.setContextClassLoader().  This custom classloader would look for
the third-party library jars in a spot I specify so it would find the
correct ones.  Since I want to change the usual classloader behavior of
"look in parent classloaders first, then child classloader" to "look in
child classloader first, then in parent classloaders" I can't just
override ClassLoader.findClass().  I, at a minimum, have to override
ClassLoader.loadClass() to look in my classloader first.  I have
questions about this:

1. What other methods do I have to override?  For example, which of the
resource-related methods do I need to override so that resources are
searched for first in my classloader then in parent classloaders?

2. I was thinking of using a URLClassLoader as a helper to my
classloader, invoking its method(s) from my custom classloader's
method(s) to actually load the classes from URLs that are not on the
standard classpath.  I was planning to set it up with a custom parent
classloader that can't find anything, so that the helper URLClassLoader
would only ever find classes/resources in the URLs I provide to it.
Does this approach make sense?  Have you seen anything like this done
before?

Thanks in advance for any help you can provide.