Learn an example of PETClinic, I found that the service and DAO layers were on one. Just study, re-enable the architecture. Learn the G-Roller style, separating four DAOs such as OwnerDao, and then implement four actual DAOs such as HibernateownerDao on this basis. Finally, the four DAOs are assembled into the service through Spring, because the business is relatively simple, just a service is implemented.
I have finished thinking, I feel clearer with J2EE's architecture.
