spring-测试IOC创建对象

1.编写UserDao接口

public interface UserDao {
    public void getUser();
}

2.给UserDao编写两个对应的实现类

public class UserDaoMysqlImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("Mysql获取用户数据");
    }
}

public class UserDaoOracleImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("Oracle获取用户数据");
    }
}

3.编写UserService接口

public interface UserService {
    void getUser();
}

4.编写UserService的实现类

public class UserServiceImpl implements UserService{
    private UserDao userDao;
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
    @Override
    public void getUser() {
        userDao.getUser();
    }
}

5.编写配置文件,将需要创建的对象注册在配置文件中

首先是通过mysqlImpl实现,只需要将mysqlImpl注入到UserServiceImpl中的UserDao属性

<?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="mysqlImpl" class="com.lv.dao.UserDaoMysqlImpl"/>
    <bean id="oracleImpl" class="com.lv.dao.UserDaoOracleImpl"/>
<!--    ref : 引用Spring容器中创建好的对象
        value : 具体的值,基本数据类型
-->
    <bean id="UserServiceImpl" class="com.lv.service.UserServiceImpl">
        <property name="userDao" ref="mysqlImpl"/>
    </bean>
</beans>

6.测试

6.1测试代码

public class MyTest {
    public static void main(String[] args) {
        //获取ApplicationContext : 拿到spring的容器
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        //拿到容器后,需要什么,就用容器get什么
        UserServiceImpl userServiceImpl = (UserServiceImpl) context.getBean("UserServiceImpl");
        userServiceImpl.getUser();
    }
}

6.2.执行结果

7.修改UserDao的实现类

7.1修改配置文件

通常修改一个接口的实现类需要重新new一个新的实现类,相当于更改了程序本身,使用IOC之后只需要修改配置文件就可以,将配置文件中UserServiceImpl的UserDao属性注入更改为oracleImpl

<bean id="UserServiceImpl" class="com.lv.service.UserServiceImpl">
    <property name="userDao" ref="oracleImpl"/>
</bean>

测试代码不需要改变

7.2执行结果