为什么在springmvc.xml文件中添加<context:component-scan>标签后,还创建bean失败

Question

下面的Spring mvc代码中,为什么创建bean失败,我已经在springmvc.xml文件中添加<context:component-scan base-package="">了啊

其中,项目目录结构为:

项目报错原因：
Caused by:
org.springframework.beans.factory.BeanCreationException:
Could not autowire field:
private com.atguigu.springmvc.UserService com.atguigu.springmvc.HelloWorld.userService;
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:
No qualifying bean of type [com.atguigu.springmvc.UserService] 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)}

下面是文件的具体代码：

其中web.xml文件:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">

    
    <servlet>
        <servlet-name>springDispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>springDispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
</web-app>

springmvc.xml文件:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">


    <context:component-scan base-package="com.atguigu.springmvc"/>
    
    <!-- 配置视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>
</beans>

HelloWorld.java文件

@Controller
public class HelloWorld {

    @Autowired
    private UserService userService;
    
    public HelloWorld() {
        System.out.println("HelloWorld Constructor...");
    }
    
    @RequestMapping("/helloworld")
    public String hello(){
        System.out.println("success");
        return "success";
    }
    
}

UserService.java

@Service
public class UserService {

    @Autowired
    private HelloWorld helloWorld;
    
    public UserService() {
        System.out.println("UserService Constructor...");
    }
    
}

Answer 1

看看UserService.java中@Service注解包引错了没有，可能导成非org.springframework.stereotype.Service了

Answer 2

HelloWorld是Controller，UserService是Service，那为什么要在Service里面注入Controller呢，属于递归调用了，肯定会报错的呀