Sorry for being a little late on this, but for behavior-changing attributes one technique which I have practiced is to make all fields final and when changes are needed I swap out the implementation since my enclosing system is thread-safe.
For example, the filter and protocol chains are thread-safe and allow adding and removing (and replacing?) filters & protocols in a thread-safe manner. This is a very heavyweight technique for variables which change frequently, but in my systems it performs quite well and provides explicit transactional behavior when a change is needed. I don't mind feedback on this idea and I will certainly understand if you find this approach is not applicable to MINA. ;) -karl
