c50 --- (The dataSource bean, The transactionManager bean, Component
scan, JPA EntityManagerFactory bean)
	@Service annotation is to identify that it’s a Spring component that
provides business services to another layer and assigns
		the Spring bean the name XXX.
	@Repository annotation indicates that the class contains data access
logic and instructs Spring to translate the vendor-specific exceptions
to Spring’s
		DataAccessException hierarchy.
	@PersistenceContext to inject EntityManager.
	For Hibernate’s JPA implementation, the default fetching strategy is
still lazy.