As a Spring bigot and an exponent of SOA for many years I'd advise Spring remoting. This flavour of service exporter will do the trick for RMI.
org.springframework.remoting.rmi.RmiServiceExporter
Other transports are of course available. The serialisation thing is quite managable if you version your interfaces (end-points) and DTOs sensibly & manage serialisation UUIDs properly. We postfix 'Alpha', 'Bravo' to our interfaces and objects and increment, decrement & reinvent where and when necessary. We also fix our serialisation UUIDs to 1 and ensure changes are only addative, otherwise we move from say, 'Bravo' to 'Charlie'. All managable in an Enterprise setup.
