1.早期對(duì)象創(chuàng)建(什么時(shí)候用到，什么時(shí)候自己手動(dòng)創(chuàng)建)

public void testSave1() {
    UserDao userDao = new UserDaoImpl();
    userDao.save();
}

2.對(duì)象由工廠創(chuàng)建(其實(shí)這里已經(jīng)有控制反轉(zhuǎn)的意思，對(duì)象創(chuàng)建由手動(dòng)創(chuàng)建轉(zhuǎn)移到工廠創(chuàng)建)

public class BeanFactory {
    public static UserDao getUserDao() {
        return new UserDaoImpl(); // 還可以做成配置文件反射做
    }
}
public void testSave2() {
    UserDao userDao = BeanFactory.getUserDao();
    userDao.save();
}

3.具體看看Spring做法

<?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 
                           http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="userDao" class="com.boomsecret.ioc.UserDaoImpl"/>
</beans>

public void testSave3() {
    String configPath = "com/boomsecret/ioc/bean.xml";
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext(configPath);
    UserDao userDao = applicationContext.getBean("userDao", UserDao.class);
    userDao.save();
}

4.總結(jié)

Spring其實(shí)就是一個(gè)大工廠，可以產(chǎn)生各種Bean