Unsatisfied dependency expressed through field dao，千万不要画蛇添足

各位小伙伴千万别画蛇添足。使用Springboot的时候。当你想用两个数据库查询两张表提高数据库的性能，你可千万得看好了

Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: 
Error creating bean with name 'teacherGradeController': Unsatisfied dependency expressed through field 'service'; 
nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'teacherGradeServiceImpl': Unsatisfied dependency expressed through field 'dao'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'com.qf.dao.TeacherGradeDao' available: expected single matching bean but found 2: teacherGradeDaoImpl,teacherGradeDao

Description:

Field dao in com.qf.service.Impl.TeacherGradeServiceImpl required a single bean, but 2 were found:
	- teacherGradeDaoImpl: defined in file [E:\Protect\springboot\springbootInterceptor\target\classes\com\qf\dao\Impl\TeacherGradeDaoImpl.class]
	- teacherGradeDao: defined in file [E:\Protect\springboot\springbootInterceptor\target\classes\com\qf\dao\TeacherGradeDao.class]


Action:

Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed

这个错误，其实就在你的启动类，一方面是看看放在哪里，你如果放在子包里则他不会扫描的，比如放在（bean，service。。。）这种的父包，他才会扫描这个。
还有一种就是你是不是在启动类中写入 @MapperScan（dao层） 这个玩意，千万别写，这个注解的意思就是扫描dao层包的接口，因为你在这个查询两个数据库的时候，他是有dao层的实现类的，你在扫描dao接口的注解你肯定找不到，所以方法就是 删除再启动类中写的 @MapperScan 就OK了

@Primary 这个是标明哪个是主库
如果是双数据库的话 最好是在每个dao层上面写上 @Mapper