2、IOC理论推导

1、引入依赖

<dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-webmvc</artifactId>
   <version>4.0.3.RELEASE</version>
</dependency>

建议引入这个，他会自动下载相关的包

1、Dao

2、service（如果不使用Beans.xml，我们可以用Set接口实现注入）

3、Beans

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


    <bean id="MysqlImpl" class="com.xiong.dao.UserMysqlImpl"/>
    <bean id="OracleImpl" class="com.xiong.dao.UserOracleImpl"/>
    <bean id="SqlservlceImpl" class="com.xiong.dao.UserSqlservlceImpl"/>

    <bean id="ServiceImpl" class="com.xiong.service.UserServiceImpl">
        <property name="userDao" ref="OracleImpl"/>
    </bean>
</beans>

5、Test

public class Mytest {
    public static void main(String[] args) {

        //获取ApplicationContext，拿到Spring中的容器
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        //需要什么拿什么
        UserServiceImpl userServiceImpl = (UserServiceImpl) context.getBean("ServiceImpl");
        userServiceImpl.getUser();

/*        //用户实际调用的是业务层，dao层他们不需要接触
        UserService userService = new UserServiceImpl();
        ((UserServiceImpl) userService).setUserDao(new UserSqlservlceImpl());
        userService.getUser();*/
    }

}