在網上看到一個比較好的O/R指南http://www.xylax.net/hibernate/
1. Simple Association (one to one)
2. Simple Reference (many to one)
3. Basic Collection (one to many)
4. Collection (many to many)
5. Collection (raw data)
6. Top-level Collections
7. Map
8. Entity Map
9. Subclasses
10. Joined Subclasses
11. Components
12. Collections of Components
13. Composite Id
14. Composite Index
15. Ternary Associations