設計模式——命令模式

命令模式：

將請求封裝成對象，從而使用不一樣的請求、隊列以及日誌來參數化其餘對象。命令對象支持可撤銷的操做。命令對象將動做和接收者包進對象中。實現「行爲請求者」與「行爲實現者」解耦。

要點： 命令對象中動做和接收者被綁在一塊兒，控制器調用命令對象的execute方法。

應用： 線程池、隊列請求、日誌請求。

類圖：

 

如下程序模擬一個控制器對客廳的燈和車庫的門進行控制。

1.定義燈

package net.dp.command.simpleremote;

public class Light {

	public Light() {
	}

	public void on() {
		System.out.println("Light is on");
	}

	public void off() {
		System.out.println("Light is off");
	}
}

　　

2.定義車庫的門

package net.dp.command.simpleremote;

public class GarageDoor {

	public GarageDoor() {
	}

	public void up() {
		System.out.println("Garage Door is Open");
	}

	public void down() {
		System.out.println("Garage Door is Closed");
	}

	public void stop() {
		System.out.println("Garage Door is Stopped");
	}

	public void lightOn() {
		System.out.println("Garage light is on");
	}

	public void lightOff() {
		System.out.println("Garage light is off");
	}
}

　　

3.定義命令接口

package net.dp.command.simpleremote;

public interface Command {
	public void execute();
}

　　

4.實現命令接口

package net.dp.command.simpleremote;

public class LightOnCommand implements Command {
	Light light;
  
	public LightOnCommand(Light light) {
		this.light = light;
	}
 
	public void execute() {
		light.on();
	}
}

　　

package net.dp.command.simpleremote;

public class LightOffCommand implements Command {
	Light light;
 
	public LightOffCommand(Light light) {
		this.light = light;
	}
 
	public void execute() {
		light.off();
	}
}

　　

package net.dp.command.simpleremote;

public class GarageDoorOpenCommand implements Command {
	GarageDoor garageDoor;

	public GarageDoorOpenCommand(GarageDoor garageDoor) {
		this.garageDoor = garageDoor;
	}

	public void execute() {
		garageDoor.up();
	}
}

　　

5.編寫控制器，實現命令的調用

package net.dp.command.simpleremote;

//
// This is the invoker
//
public class SimpleRemoteControl {
	Command slot;
 
	public SimpleRemoteControl() {}
 
	public void setCommand(Command command) {
		slot = command;
	}
 
	public void buttonWasPressed() {
		slot.execute();
	}
}

　　

6.寫完啦！！

package net.dp.command.simpleremote;

public class RemoteControlTest {
	public static void main(String[] args) {
		SimpleRemoteControl remote = new SimpleRemoteControl();
		Light light = new Light();
		GarageDoor garageDoor = new GarageDoor();
		LightOnCommand lightOn = new LightOnCommand(light);
		GarageDoorOpenCommand garageOpen = new GarageDoorOpenCommand(garageDoor);

		remote.setCommand(lightOn);
		remote.buttonWasPressed();
		remote.setCommand(garageOpen);
		remote.buttonWasPressed();
	}
}