Spring IOC和DI实现原理及实例解析

package com.ssm.entry;

public class UserServiceImpl implements UserService {

	private UserDao userDao;
	
	// setter()实现依赖注入
	public void setUserDao(UserDao userDao){
		this.userDao = userDao;
	}
	
	public void login() {
		this.userDao.login();
		System.out.println("UserService login");
	}

}

<?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-4.3.xsd">
    		
    <!-- 将指定类配置给Spring，让Spring创建其对象的实例 控制反转 -->
		<bean id="UserDao" class="com.ssm.entry.UserDaoImpl"></bean>
		
		<!-- 添加一个id为userService的Bean 依赖注入-->
		<bean id="UserService" class="com.ssm.entry.UserServiceImpl">
			<!-- 将name为UserDao的Bean注入UserService实例中 -->
			<property name="UserDao" ref="UserDao"/>
		</bean>
</beans>

package com.ssm.entry;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class IoC {
	public static void main(String[] args) {
		
		ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
		UserDao userDao = (UserDao)applicationContext.getBean("UserDao");
		userDao.login();
		
	}
}

package com.ssm.entry;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class DI {
	
	public static void main(String[] args) {
		ApplicationContext applicationContext = new 
				ClassPathXmlApplicationContext("applicationContext.xml");
		UserService userService = (UserService)applicationContext.getBean("UserService");
		userService.login();
	}
	
}