How do poeple make application contexts runtime configurable?

Hi,
let's say I have a web application and I have some configurables in it (e.g., database connection).
I want it to be runtime configurable. I looked at JMX, but it seems there's no way to persist modifications to the beans with JBoss (the current target for deployement, but that may change).
Any other solution people are using?
I was thinking of a simple property file in the WEB-INF/classes, and a web page to modify its contents. But... how do I reload the application context after the modifications?