相关代码：<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">
     <bean id="bookDao" class="com.imooc.spring.ioc.bookshop.dao.BookDaoOracleImpl">

     </bean>
</beans>

相关代码：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="bookService" class="com.imooc.spring.ioc.bookshop.service.BookService">
        <property name="bookDao" ref="bookDao"/>
    </bean>
</beans>

相关截图：

问题描述：

BookShopApplication中可以正常输出，就是不明白xml中为啥ref是红色的