设计模式 - 外观模式(facade pattern) 详解

外观模式(facade pattern) 详解

本文地址: http://blog.csdn.net/caroline_wendy

外观模式(facade pattern): 提供了一个统一的接口, 用来访问子系统中的一群接口. 外观定义了一个高层接口, 让子系统更容易使用.

外观模式包含三个部分:

1. 子系统: 子类, 单个复杂子类 或 多个子类;

2. 外观(facade)类: 把子系统设计的更加容易使用;

3. 客户: 只需要调用外观类.

与适配器模式(adapter pattern)的区别:

适配器模式的意图是, "改变"接口符合客户的期望; 外观模式的意图是, 提供子系统的一个简化接口.

面向对象的设计原则:

最少知识原则: 只和你的密友交谈.

具体方法:

1. 外观(facade)类, 包含多个子类的组合, 和一些调用多个子类的接口:

package facade;

public class HomeTheaterFacade {

	Amplifier amp;
	Tuner tuner;
	DvdPlayer dvd;
	CdPlayer cd;
	Projector projector;
	TheaterLights lights;
	Screen screen;
	PopcornPopper popper;

	public HomeTheaterFacade(Amplifier amp,
			Tuner tuner,
			DvdPlayer dvd,
			CdPlayer cd,
			Projector projector,
			TheaterLights lights,
			Screen screen,
			PopcornPopper popper) {
		// TODO Auto-generated constructor stub
		this.amp = amp;
		this.tuner = tuner;
		this.dvd = dvd;
		this.cd = cd;
		this.projector = projector;
		this.lights = lights;
		this.screen = screen;
		this.popper = popper;
	}

	public void watchMovie(String movie) {
		System.out.println("Get ready to watch a movie...");
		popper.on();
		popper.pop();
		lights.dim(10);
		screen.down();
		projector.on();
		projector.wideScreenMode();
		amp.on();
		amp.setDvd(dvd);
		amp.setSurroundSound();
		amp.setVolume(5);
		dvd.on();
		dvd.play(movie);
	}

	public void endMovie() {
		System.out.println("Shutting movie threater down...");
		popper.off();
		lights.on();
		screen.up();
		projector.off();
		amp.off();
		dvd.stop();
		dvd.eject();
		dvd.off();
	}

}

2. 测试类, 只需要调用子类的接口, 即可.

/**
 * @time 2014年6月17日
 */
package facade;

/**
 * @author C.L.Wang
 *
 */
public class HomeTheaterTestDrive {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Amplifier amp = new Amplifier("Top-O-Line Amplifier");
		Tuner tuner = new Tuner("Top-O-Line AM/FM Tuner", amp);
		DvdPlayer dvd = new DvdPlayer("Top-O-Line DVD Player", amp);
		CdPlayer cd = new CdPlayer("Top-O-Line CD Player", amp);
		Projector projector = new Projector("Top-O-Line Projector", dvd);
		TheaterLights lights = new TheaterLights("Theatera Ceiling Lights");
		Screen screen = new Screen("Theater Screen");
		PopcornPopper popper = new PopcornPopper("Popcorn Popper");

		HomeTheaterFacade homeTheater =
				new HomeTheaterFacade(amp, tuner, dvd, cd, projector, lights, screen, popper);

		homeTheater.watchMovie("Who is a girl? ");
		homeTheater.endMovie();
	}

}

3. 输出:

Get ready to watch a movie...
Popcorn Popper on
Popcorn Popper popping popcorn!
Theater Ceiling Lights dimming to 10%
Theater Screen going down
Top-O-Line Projector on
Top-O-Line Projector in widescreen mode (16x9 aspect ratio)
Top-O-Line Amplifier on
Top-O-Line Amplifier setting DVD player to Top-O-Line DVD Player
Top-O-Line Amplifier surround sound on (5 speakers, 1 subwoofer)
Top-O-Line Amplifier setting volume to 5
Top-O-Line DVD Player on
Top-O-Line DVD Player playing "Who is a girl? "
Shutting movie threater down...
Popcorn Popper off
Theater Ceiling Lights on
Theater Screen going up
Top-O-Line Projector off
Top-O-Line Amplifier off
Top-O-Line DVD Player stopped "Who is a girl? "
Top-O-Line DVD Player eject
Top-O-Line DVD Player off

4. 子类其余代码下载: http://download.csdn.net/detail/u012515223/7511683

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