設(shè)計模式_18_中介者模式

基本介紹

中介者模式(Mediator Pattern)炭分，用一個中介對象來封裝一系列的對象交互桃焕。中介者使各個對象不需要顯式地相互引用，從而使其耦合松散捧毛，而且可以獨立地改變它們之間的交互
中介者模式屬于行為型模式观堂，使代碼易于維護
比如MVC模式，C (Controller控制器)是M (Model模型)和V (View視圖)的中介者呀忧，在前后端交互時起到了中間人的作用

image.png

例子：
智能家庭項目:
1)智能家庭包括各種設(shè)備师痕，鬧鐘、咖啡機而账、電視機胰坟、窗簾等
2)主人要看電視時，各個設(shè)備可以協(xié)同工作泞辐，自動完成看電視的準(zhǔn)備工作笔横，比如流
程為:鬧鈴響起->咖啡機開始做咖啡->窗簾自動落下->電視機開始播放

實現(xiàn)：

image.png

public abstract class Mediator {    
    
    public abstract void getMessage(int stateChange,String name);
    
    public abstract void register(String name,Colleage colleage);
    
    public abstract void sendMessage();
}

public abstract class Colleage {

    private Mediator mediator;
    public String name;
    public Colleage(Mediator mediator, String name) {
        super();
        this.mediator = mediator;
        this.name = name;
    }

public class ConcereteMediator extends Mediator{
    
     private HashMap<String, Colleage> map;
     private HashMap<String, String> interMap;

     public ConcereteMediator() {
        // TODO Auto-generated constructor stub
        map = new HashMap<>();
        interMap = new HashMap<>();
     }
    
    @Override
    public void getMessage(int stateChange,String name) {
        // TODO Auto-generated method stub
        Colleage colleage = map.get(name);
        if (colleage instanceof Alarm) {
            if (stateChange == 0) {
                ( (TV)(map.get(interMap.get("TV"))) ).play();
                ( (CoffeeMachine)(map.get(interMap.get("CoffeeMachine"))) ).play();
            }else if (stateChange == 1) {
                ( (TV)(map.get(interMap.get("TV"))) ).stop();
                ( (CoffeeMachine)(map.get(interMap.get("CoffeeMachine"))) ).stop();
            }
        }else if(colleage instanceof TV){
            
        }
        
    }
    
    public void register(String name,Colleage colleage) {
        map.put(name, colleage);
        
        if (colleage instanceof Alarm) {
            interMap.put("Alarm", name);
        }else if (colleage instanceof TV) {
            interMap.put("TV", name);       
        }else if(colleage instanceof CoffeeMachine){
            interMap.put("CoffeeMachine", name);
        }
    }

    @Override
    public void sendMessage() {
        // TODO Auto-generated method stub
        
    }

}
    
    public Mediator getMediator(){
        return this.mediator;
    }
    
    public abstract void sendMessage(int stateChange);
}

public class Alarm extends Colleage {

    public Alarm(Mediator mediator, String name) {
        super(mediator, name);
        // TODO Auto-generated constructor stub
        mediator.register(name, this);
    }
    

    @Override
    public void sendMessage(int stateChange) {
        // TODO Auto-generated method stub
        this.getMediator().getMessage(stateChange,this.name);
    }
    
    @Override
    public Mediator getMediator() {
        // TODO Auto-generated method stub
        return super.getMediator();
    }
}

public class TV extends Colleage{

    public TV(Mediator mediator, String name) {
        super(mediator, name);
        // TODO Auto-generated constructor stub
        mediator.register(name, this);
    }

    @Override
    public void sendMessage(int stateChange) {
        // TODO Auto-generated method stub
        this.getMediator().getMessage(stateChange,this.name);
    }
    
    @Override
    public Mediator getMediator() {
        // TODO Auto-generated method stub
        return super.getMediator();
    }

    public void play() {
        // TODO Auto-generated method stub
        System.out.println("電視開始播放...");
    }
    
    public void stop() {
        // TODO Auto-generated method stub
        System.out.println("電視停止播放");
    }

}

public class CoffeeMachine extends Colleage {

    public CoffeeMachine(Mediator mediator, String name) {
        super(mediator, name);
        // TODO Auto-generated constructor stub
        mediator.register(name, this);
    }

    @Override
    public void sendMessage(int stateChange) {
        // TODO Auto-generated method stub
        this.getMediator().getMessage(stateChange,this.name);
    }
    
    @Override
    public Mediator getMediator() {
        // TODO Auto-generated method stub
        return super.getMediator();
    }

    public void play() {
        // TODO Auto-generated method stub
        System.out.println("咖啡機開始工作...");
    }
    
    public void stop() {
        // TODO Auto-generated method stub
        System.out.println("咖啡機停止工作...");
    }

}

public class Client {
    
    public static void main(String[] args) {

        Mediator mediator = new ConcereteMediator();
        
        Alarm alarm = new Alarm(mediator, "Alarm");
        
        TV tv = new TV(mediator, "Tv");
        
        CoffeeMachine coffeeMachine = new CoffeeMachine(mediator, "coffeMachine");
        
        alarm.sendMessage(0);
        System.out.println("----------------");
        alarm.sendMessage(1);
    }
}

中介者模式的注意事項和細節(jié)

多個類相互耦合，會形成網(wǎng)狀結(jié)構(gòu),使用中介者模式將網(wǎng)狀結(jié)構(gòu)分離為星型結(jié)構(gòu)咐吼，進行解耦
減少類間依賴狠裹，降低了耦合，符合迪米特原則
中介者承擔(dān)了較多的責(zé)任汽烦，一旦中介者出現(xiàn)了問題涛菠，整個系統(tǒng)就會受到影響
如果設(shè)計不當(dāng)，中介者對象本身變得過于復(fù)雜，這點在實際使用時俗冻，要特別注意