一、需求

妈妈在早餐后给三个孩子分发餐后水果 ，盘子里装有三个苹果: 红富士、青苹果、金帅，孩子们口味不同: 莉莉喜欢甜的，安迪喜欢酸的，露娜喜欢软的。

二、需求实现

package com.imooc.spring.ioc.entity;

public class Apple {
    private String title;
    private String color;
    private String origin;

    public Apple() {
    }

    public Apple(String title, String color, String origin) {
        this.title = title;
        this.color = color;
        this.origin = origin;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public String getOrigin() {
        return origin;
    }

    public void setOrigin(String origin) {
        this.origin = origin;
    }
}

package com.imooc.spring.ioc.entity;

public class Child {
    private String name;
    private Apple apple;

    public Child(){

    }

    public Child(String name, Apple apple) {
        this.name = name;
        this.apple = apple;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Apple getApple() {
        return apple;
    }

    public void setApple(Apple apple) {
        this.apple = apple;
    }

    public void eat(){
        System.out.println(name + "吃到了" + apple.getOrigin() + "种植的" + apple.getTitle());
    }
}

package com.imooc.spring.ioc;

import com.imooc.spring.ioc.entity.Apple;
import com.imooc.spring.ioc.entity.Child;

public class Application {
    public static void main(String[] args) {
        Apple apple1 = new Apple("红富士", "红色", "欧洲");
        Apple apple2 = new Apple("青苹果", "绿色", "中亚");
        Apple apple3 = new Apple("金帅", "黄色", "中国");

        Child lily = new Child("莉莉", apple3);
        Child andy = new Child("安迪", apple2);
        Child luna = new Child("露娜", apple1);

        lily.eat();
        andy.eat();
        luna.eat();
    }
}

三、代码分析

问题一：文本的信息写死在代码中，如果属性发生变化，那么就要修改源代码，这是很不合理的。

问题二：对象的数量都是固定写死的，如果需要新增对象，这会让可扩展性不足。

问题三：对象是硬性关联，通过构造方法参数传入到对应参数中进行赋值，也就意味着，孩子和苹果的关系在编译时就已经确定了。

四、解决方法

利用IOC容器降低对象之间的直接耦合，将对象都交由Spring IOC创建和管理。

以下是代码实现：

<?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">
    <!-- SpringIOC的核心配置文件，所有对象的创建和关联设置都是在这个xml中进行的。-->
    <!--在IOC容器启动时，自动由Spring实例化Apple对象，取名sweetApple放入到容器中-->
    <bean id="sweetApple" class="com.imooc.spring.ioc.entity.Apple">
        <property name="title" value="红富士"></property>
        <property name="origin" value="欧洲"></property>
        <property name="color" value="红色"></property>
    </bean>

    <bean id="sourApple" class="com.imooc.spring.ioc.entity.Apple">
        <property name="title" value="青苹果"></property>
        <property name="origin" value="中亚"></property>
        <property name="color" value="绿色"></property>
    </bean>

    <bean id="softApple" class="com.imooc.spring.ioc.entity.Apple">
        <property name="title" value="金帅"></property>
        <property name="origin" value="中国"></property>
        <property name="color" value="黄色"></property>
    </bean>

    <bean id="lily" class="com.imooc.spring.ioc.entity.Child">
        <property name="name" value="莉莉"/>
        <property name="apple" ref="sweetApple"/>
    </bean>

    <bean id="andy" class="com.imooc.spring.ioc.entity.Child">
        <property name="name" value="安迪"/>
        <property name="apple" ref="sourApple"/>
    </bean>

    <bean id="luna" class="com.imooc.spring.ioc.entity.Child">
        <property name="name" value="露娜"/>
        <property name="apple" ref="softApple"/>
    </bean>

    </beans>

package com.imooc.spring.ioc;

import com.imooc.spring.ioc.entity.Apple;
import com.imooc.spring.ioc.entity.Child;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringApplication {
    public static void main(String[] args) {
        //创建Spring IoC容器,并根据配置文件在容器中实例化对象
        ApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
        Apple sweetApple = context.getBean("sweetApple" , Apple.class);
        System.out.println(sweetApple.getTitle());
        
        //从IoC容器中提取beanId=lily的对象
        Child lily = context.getBean("lily", Child.class);
        Child andy = context.getBean("andy", Child.class);
        Child luna = context.getBean("luna", Child.class);

        lily.eat();
        andy.eat();
        luna.eat();
    }
}

最后代码运行所得结果如下：