ssm错误dDependencyException: Error creating bean with name 'userController': Unsatisfied dependency expressed through field 'userService';

dDependencyException: Error creating bean with name 'userController': Unsatisfied dependency expressed through field 'userService'; 
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: 
No qualifying bean of type 'com.bjpowernode.blog.back.service.UserService' 
available: expected at least 1 bean which qualifies as autowire candidate.
 Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

原因：service层的注解没有写

解决办法

检查 dao层（@param可不写）

service层（@Server） 

controller层（@Controller）