设计模式:外观模式(Facade)

    外观模式(Facade)也叫过程模式， 外观模式为子系统中的一组接口提供一个一致的界面，此模式定义了一个高层接口,这个接口使得这一子系统更加容易使用。

    外观模式通过定义一个一致的接口,用以屏蔽内部子系统的细节,使得调用端只需跟这个接口发生调用，而无需关心这个子系统的内部细节。

  

  外观类(Facade): 为调用端提供统一的调用接口,外观类知道哪些子系统负责处理请求，从而将调用端的请求代理给适当的子系统对象。

  子系统的集合: 指模块或子系统，处理Facade对象指派的任务,他是功能的实际提供者。

  外观模式在MyBatis框架中的应用：MyBatis中的Configuration去创建MetaObject对象使用到外观模式。

用外观模式模拟一个电影院

public class DVDPlayer {
	
	private static DVDPlayer instance = new DVDPlayer();
	
	private DVDPlayer(){}
	
	public static DVDPlayer getInstance(){
		return instance;
	}
	
	public void play(){
		System.out.println(" dvd is playing ");
	}
	
	public void on(){
		System.out.println(" dvd on ");
	}
	
	public void off(){
		System.out.println(" dvd off ");
	}
	
	public void pause(){
		System.out.println(" dvd pause ");
	}
}


// 爆米花
public class Popcorn {
	
	private static Popcorn instance = new Popcorn();
	
	private Popcorn(){}
	
	public static Popcorn getInstance(){
		return instance;
	}
	
	
	public void on(){
		System.out.println(" Popcorn on ");
	}
	
	public void off(){
		System.out.println(" Popcorn off ");
	}
	
	public void pop(){
		System.out.println(" Popcorn is poping ");
	}
}


// 投影机
public class Projector {
	
	private static Projector instance = new Projector();
	
	private Projector(){}
	
	public static Projector getInstance(){
		return instance;
	}
	
	public void on(){
		System.out.println(" Projector on ");
	}
	
	public void off(){
		System.out.println(" Projector off ");
	}
	
	public void focus(){
		System.out.println(" Projector is focus ");
	}
}


// 屏幕
public class Screen {
	
	private static Screen instance = new Screen();
	
	private Screen(){}
	
	public static Screen getInstance(){
		return instance;
	}
	
	public void up(){
		System.out.println(" Screen up ");
	}
	
	public void down(){
		System.out.println(" Screen down ");
	}
	
}


// 影院立体声
public class Stereo {
	
	private static Stereo instance = new Stereo();
	
	private Stereo(){}
	
	public static Stereo getInstance(){
		return instance;
	}
	
	public void on(){
		System.out.println(" Stereo on ");
	}
	
	public void off(){
		System.out.println(" Stereo off ");
	}
	
	public void up(){
		System.out.println(" Stereo up ");
	}
	
	public void down(){
		System.out.println(" Stereo down ");
	}
}


// 灯光
public class TheaterLight {
	
	private static TheaterLight instance = new TheaterLight();
	
	private TheaterLight(){}
	
	public static TheaterLight getInstance(){
		return instance;
	}
	
	public void on(){
		System.out.println(" TheaterLight on ");
	}
	
	public void off(){
		System.out.println(" TheaterLight off ");
	}
	
	public void dim(){
		System.out.println(" TheaterLight dim ");
	}
	
	public void bright(){
		System.out.println(" TheaterLight bright ");
	}
}


// 外观
public class HomeTheaterFacade {
	
	private DVDPlayer dvdPlayer;
	private Popcorn popcorn;
	private Projector projector;
	private Screen screen;
	private Stereo stereo;
	private TheaterLight theaterLight;
	
	public HomeTheaterFacade(){
		super();
		this.dvdPlayer = DVDPlayer.getInstance();
		this.popcorn = Popcorn.getInstance();
		this.projector = Projector.getInstance();
		this.screen = Screen.getInstance();
		this.stereo = Stereo.getInstance();
		this.theaterLight = TheaterLight.getInstance();
	}
	
	public void read(){
		popcorn.on();
		popcorn.pop();
		screen.down();
		projector.on();
		stereo.on();
		dvdPlayer.on();
		theaterLight.dim();
	}
	
	public void play(){
		dvdPlayer.play();
	}
	
	public void pause(){
		dvdPlayer.pause();
	}
	
	public void end(){
		popcorn.off();
		theaterLight.bright();
		screen.up();
		projector.off();
		stereo.off();
		dvdPlayer.off();
	}
}


public class Client {
	public static void main(String[] args){
		HomeTheaterFacade facade = new HomeTheaterFacade();
		facade.read();
		facade.play();
		facade.end();
	}
}