需依來源/條件產出bean時, 讓物件implements相同interface, 之後可用@Autowired List<物件>設定, 取用所有物件
依來源/條件產出bean, 並將來源/條件設為enum, 關聯物件及enum值存在map以取用
bean建構子傳不特定參數寫法
bean裡需依情況在建構子inject不同設定(e.g.api代碼,來源別...)寫法
types of Dependency Injections: field, setter, constructor.
spring configuration: XML, Java code or annotations.
Instantiating beans.
Bean Lifecycle.