markfisher/spring-integration — comment on commit 9d7a3f37cf3c566db2268a03897807cc67b00e47
File:  line 0
By garyrussell:

Re: Router and Splitter

While it is unlikely Spring will have proxied an abstract class at this time, it is (albeit remotely) possible that a user might expose a proxy for an AbstractMessage(Rout|Splitt)er via his own factory bean.

Would it make sense to create marker interfaces for MessageRouter and MessageSplitter?