mybatis整合ss的时候，无法autowire使用mapper的自动注入，找不到bean：NoSuchBeanDefinitionException

org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name ‘userDaoImpl‘: Injection of autowired dependencies failed; 
nested exception is org.springframework.beans.factory.BeanCreationException: 
Could not autowire field: private com.dao.UserMapper com.service.UserDaoImpl.userMapper; 
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.dao.UserMapper] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}