Hibernate is an Open Source ORM mapper.

ReadWriteCache - An item was expired by the cache while it was locked (increase your cache timeout)

I had the problem after turning of the 2nd level disk cache (ehcache). Seems to be ignorable.

Persistent Objects

equals and hashCode

equals and hashCode should be consistent on your classes, and depend on the same fields. Otherwise, usage in HashSets or HashMaps will cause problems. For persistent objects they should be implemented using business keys. Equals and HashCode

Xdoclet

If you are still on hibernate 2 then XDoclet will allow you to use annotations.