Proper usage of URLClassLoader for loading jars in a plugin environment

Question

Hi,
I have some questions about using a URLClassLoader in a plugin architecture. Supposing that plugin jar files can be registered and deregistered dynamically while OC4J is running, should the same class loader instance be used for the same jar file every time it is loaded (e.g., by caching them in a HashMap)? The concern is that if different class loaders are used each time and the plugin depends on some native library that may only be loaded once, there may be problems if the jar is registered more than once.
One concern about using the same loader every time is that the class loader will consult the cache the next time the same plugin jar is loaded, meaning that changes to the jar file will not be reflected the next time it is registered.
Currently, we pass Thread.currentThread().getContextClassLoader into a new URLClassLoader as the parent class loader each time a plugin jar file is registered:
URLClassLoader cl = new URLClassLoader(
urls, Thread.currentThread().getContextClassLoader()
Is this sufficient for a plugin environment as described? Will this essentially use the same class loader each time?
Thanks,
Greg

Answer 1

We use HTTP_HOST in most cases from what I can see. You may have also noted that HTTP_HOST may have :<port> appended to the hostname as well.
Scott