> for example, there will be a separate EventBus for each classloader
Not if you leave the message classes alone.
> Do you know of any frameworks that would make the idea easier to implement?
No, just careful design (JRebel is for development rather than production, as I understand, but I could be wrong) Tooting my own horn (again) but Quasar does hot code swapping for actors (including state preservation)[1]. This is possible (as it is in Erlang) because actors encapsulate their own state.
Not if you leave the message classes alone.
> Do you know of any frameworks that would make the idea easier to implement?
No, just careful design (JRebel is for development rather than production, as I understand, but I could be wrong) Tooting my own horn (again) but Quasar does hot code swapping for actors (including state preservation)[1]. This is possible (as it is in Erlang) because actors encapsulate their own state.
[1]: http://docs.paralleluniverse.co/quasar/#hot-code-swapping