总是显示serviceimpl的seckilldao属性无法注入

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'seckillServiceImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.seckill.dao.SeckillDao org.seckill.service.impl.SeckillServiceImpl.seckillDao; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.seckill.dao.SeckillDao] 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)}