【Spring】@Autowired and @Resource

Given that Spring can autowire either by type or by name, it is always confusing to me that what is the default behavior when using annocation @Autowired or @Resource to do the autowire. Therefore, I made an experiment to help clear out confusion. Here are some of my findings:

      1. By default @Autowired and @Resource will first use field name or parameter name to autowire bean with the same name as bean id. If it can't find any matching bean id, then it will autowire by type. 

      2. When autowire by type, for certain type, there must be only one bean existing in the application context. Otherwise, Spring will throw exception like: No unique bean of type [com.ms.junz.domain.User] is defined: expected single matching bean but found 2: [user1, user]

      3. If your field name is independent of bean id and there might be multiple beans with the same type, you can use either@Qualifier("beanId") together with @Autowired, or @Resource(name="beanId") to explicitly tell Spring which bean to autowire. Then, Spring wouldn't complain any longer.