IoC入门案例

步骤
①∶导入Spring坐标

<dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.10.RELEASE</version>
</dependency>

②∶定义Spring管理的类(接口),并实现

public interface BookService {
     public void save( ) ;
}
public class BookServiceImpl implements BookService {
    private BookDao bookDao = new BookDaoImpl();
    public void save() {
        bookDao. save();
    }
}

③∶创建Spring配置文件，配置对应类作为Spring管理的bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http:/ /www.springframework.org/schema/beans"
             xmlns :xsi="http:// www . w3.org/20日1/XMLSchema-instance"
             xsi:schemaLocation="http://www.springframework.org/schema/be
                      https://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="bookService" class="com.itheima. service.impl.BookServiceImpl"></bean>
</beans>

注意事项

bean定义时id属性在同一个上下文中不能重复

④∶初始化IoC容器（ Spring核心容器/Spring容器），通过容器获取bean

public class App {
    publicistatic void main(String[] args) {
        //加载配置文件得到上下文对象，也就是容器对象
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");//获取资源
        BookService bookService = (BookService) ctx.getBean("bookService");
        bookService.save();
    }
}