For reasons that remain obscure, the Hibernate developers insist on keeping the Hibernate core compatible with pre-Java5, and that means no enum support. When you try to persist an Enum field, it just serializes it, and you get binary data.
If you want to persist enums using an .hbm mapping configuration, you have to create and configure a custom
UserType for each enum type you want to handle, which is tedious and irritating. The Hibernate documentation wiki has plenty of examples, many of which seem to contradict each other, and some of which even work.
If you use Hibernate annotations, though, you get full java5 support, including automatic handling of java5 enums. It's just a real shame that you have to do one or the other.