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();} }

  

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