具體錯誤：
No qualifying bean of type [java.lang.String] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {}
原因:
1.對應要注入的實現類沒有 加注解，如dao層 @Repository 如service層 @Service
2."You generally autowire to your interface type and not impl."調用的接口是否有具體的實現類。
3.@Autowired下面，沒有類，直接跟了@RequestMapping。【我報錯的原因。無語....】