Error creating bean with name 'userController'

Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException:
 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.boron.service.UserService' available: expected at least 1 bean which qualifies as autowire candidate. 
Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

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原因：service层没有加注解
在搭spring mvc框架时，ide不会报错但会有编译错误的几个注意事项：
1.controller 加注解

@Controller 而不是@RestController
@RequestMapping("/user")

2.service加注解

@Service
@Autowired

3.dao 加注解和实现接口
@Param("")