持久层，服务层，表现层都涉及到了。
这个分得确实比DJANGO细致，
多体会，多注解。。：）
The domain layer
The persistence layer
A persistence layer usually contains repository objects to
access domain objects. A repository object makes queries to the data source for the data,
thereafter maps the data from the data source to a domain object, and finally, persists the
changes in the domain object to the data source. So, a repository object is typically
responsible for CRUD operations ( Create , Read , Update , and Delete ) on domain objects.
The @Repository annotation ( org.springframework.stereotype.Repository ) is an
annotation that marks a specific class as a repository.
The service layer：
Controller Layer:
view jsp:
