2.3依赖倒转原则

···
1.错误示范

package com.kris.designmode.principle.dependenceinversion;
public class DependenceInversion {
    public static void main(String[] args) {
        Person person = new Person();
        person.receive(new Email());
    }
}
/**
 * 实现一个Person类，接受消息
 * 方式1分析
 * 1.简单，比较容易想到
 * 2.如果获取的对象是微信，短信等，需要增加类，同时Person需要增加相应的接收方法
 * 3.解决，引入一个抽象的接口IMessage，表示接收的内容，这样Person类与IMessage接口发生依赖
 *      因为Email，WeiXin 等，属于接收的范围，各自实现IMessage
 */
class Person{
    public void receive(Email email){
        System.out.println(email.getInfo());
    }
}
class Email{
    public String getInfo(){
        return "email info : hello world";
    }
}

2.正确示范

package com.kris.designmode.principle.dependenceinversion.improve;
public class DependenceInversion2 {
    public static void main(String[] args) {
        //客户端无需改变
        Person person = new Person();
        person.receive(new Email());
        person.receive(new Wechat());
    }
}
/**
 * Person与IMessage接口发生依赖
 */
class Person{
    public void receive(IMessage email){
        System.out.println(email.getInfo());
    }
}
interface IMessage{
    String getInfo();
}
class Email implements IMessage{
    public String getInfo(){
        return "email info : hello world";
    }
}
class Wechat implements IMessage{
    public String getInfo(){
        return "wechat info : hello world";
    }
}

3.依赖倒转传递的方式

3.1setter方法注入依赖

package com.kris.designmode.principle.dependenceinversion.improve;
public class DependenceInversion3{
    public static void main(String[] args) {
        //客户端无需改变
        Person2 person = new Person2();
        person.setMessage(new Email2());
        person.receive();
        person.setMessage(new Wechat2());
        person.receive();
    }
}
/**
 * Person与IMessage接口发生依赖,setter方法注入依赖
 */
class Person2{
    private IMessage2 message;
    public void setMessage(IMessage2 message){
        this.message=message;
    }
    public void receive(){
        System.out.println(message.getInfo());
    }
}
interface IMessage2{
    String getInfo();
}
class Email2 implements IMessage2{
    public String getInfo(){
        return "email info : hello world";
    }
}
class Wechat2 implements IMessage2{
    public String getInfo(){
        return "wechat info : hello world";
    }
}

3.2构造方法注入依赖

package com.kris.designmode.principle.dependenceinversion.improve;
public class DependenceInversion4{
    public static void main(String[] args) {
        Person4 person = new Person4(new Email4());
        person.receive();
    }
}
/**
 * Person与IMessage接口发生依赖,setter方法注入依赖
 */
class Person4{
    public IMessage4 message;
    public Person4(IMessage4 message){
        this.message=message;
    }
    public void receive(){
        System.out.println(message.getInfo());
    }
}
interface IMessage4{
    String getInfo();
}
class Email4 implements IMessage4{
    public String getInfo(){
        return "email info : hello world";
    }
}

4.注意事项