org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.example.SpringBootJdbcDemoApplication.SpringBootJdbcDemoApplication': Unsatisfied dependency expressed through field 'userRepository': No qualifying bean of type [com.example.repositories.UserRepository] found for
 
 dependency [com.example.repositories.UserRepository]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of
 
 type [com.example.repositories.UserRepository] found for dependency [com.example.repositories.UserRepository]: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}  
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:569
 
)  
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)  

無法注入Dao中的Bean！
解決分析後來經研究發現，SpringBoot專案的Bean裝配預設規則是根據Application類所在的包位置從上往下掃描！ “Application類”是指SpringBoot專案入口類。這個類的位置很關鍵：
如果Application類所在的包為：io.github.gefangshuai.app
，則只會掃描io.github.gefangshuai.app
包及其所有子包，如果service或dao所在包不在io.github.gefangshuai.app
及其子包下，則不會被掃描！