[Head First设计模式笔记]----命令模式

命令模式定义：将“请求”封装成对象，以便使用不同的请求、队列或者日志来参数化其他对象。命令模式也支持可撤销的操作。

类图：

适用设计方案举例：实现一种遥控器，该遥控器具有七个可编程的插槽（每个都可以指定到一个不同的家电装置），每个插槽都有对应的开关按钮。这个遥控器还具备一个整体的撤销按钮。另外，多家厂商已经开发了一组Java类，例如电灯、风扇、热水器、音响设备和其他类似的可控制装置。遥控器如下图所示：

实现Code：

(1) 如下设备相关的Java类由厂商提供：

 1 //CeilingFan.java
 2 package RemoteControl.device;
 3 
 4 public class CeilingFan {
 5     String name;
 6     public CeilingFan(String str)
 7     {
 8         name = str;
 9     }
10     
11     public void on()
12     {
13         System.out.println(name + "CeilingFan On");
14     }
15 
16     public void off()
17     {
18         System.out.println(name + "CeilingFan Off");
19     }
20 }

 1 //GarageDoor.java
 2 package RemoteControl.device;
 3 
 4 public class GarageDoor {
 5     String name;
 6     public GarageDoor(String str)
 7     {
 8         name = str;
 9     }
10     
11     public void up()
12     {
13         System.out.println(name + "GarageDoor On");
14     }
15 
16     public void down()
17     {
18         System.out.println(name + "GarageDoor Off");
19     }
20 }

 1 //Light.java
 2 package RemoteControl.device;
 3 
 4 public class Light {
 5     String name;
 6     public Light(String str)
 7     {
 8         name = str;
 9     }
10     
11     public void on()
12     {
13         System.out.println(name + "Light On");
14     }
15 
16     public void off()
17     {
18         System.out.println(name + "Light Off");
19     }
20 }

 1 //Stereo.java
 2 package RemoteControl.device;
 3 
 4 public class Stereo {
 5     String name;
 6     public Stereo(String str)
 7     {
 8         name = str;
 9     }
10     
11     public void on()
12     {
13         System.out.println(name + "Stereo On");
14     }
15     
16     public void off()
17     {
18         System.out.println(name + "Stereo Off");
19     }
20     
21     public void setCD()
22     {
23         System.out.println(name + "Stereo setCD");
24     }
25     
26     public void setVolume(int num)
27     {
28         System.out.println(name + "Stereo setVolume:" + num);
29     }
30 }

(2) 将厂商提供的设备Java类库(即receiver)封装到Command类里面：

 1 //CeilingFanOffCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.CeilingFan;
 5 
 6 public class CeilingFanOffCommand implements Command{
 7     CeilingFan cf;
 8     
 9     public CeilingFanOffCommand(CeilingFan cf)
10     {
11         this.cf = cf;
12     }
13     
14     @Override
15     public void execute() 
16     {
17         cf.off();
18     }
19 
20     @Override
21     public void undo() {
22         cf.on();
23     }
24     
25 }

 1 //CeilingFanOnCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.CeilingFan;
 5 
 6 
 7 public class CeilingFanOnCommand implements Command{
 8     CeilingFan cf;
 9     
10     public CeilingFanOnCommand(CeilingFan cf)
11     {
12         this.cf = cf;
13     }
14     
15     @Override
16     public void execute() 
17     {
18         cf.on();
19     }
20     
21     @Override
22     public void undo() {
23         cf.off();
24     }
25 }

1 //Command.java
2 package RemoteControl.Command;
3 
4 public interface Command {
5     public void execute();
6     public void undo();
7 }

 1 //GarageDoorDownCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.GarageDoor;
 5 
 6 public class GarageDoorDownCommand implements Command {
 7     GarageDoor gd;
 8     
 9     public GarageDoorDownCommand(GarageDoor gd)
10     {
11         this.gd = gd;
12     }
13     
14     @Override
15     public void execute() 
16     {
17         gd.down();
18     }
19 
20     @Override
21     public void undo() {
22         gd.up();
23     }
24 }

 1 //GarageDoorUpCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.GarageDoor;
 5 
 6 public class GarageDoorUpCommand implements Command {
 7     GarageDoor gd;
 8     
 9     public GarageDoorUpCommand(GarageDoor gd)
10     {
11         this.gd = gd;
12     }
13     
14     @Override
15     public void execute() 
16     {
17         gd.up();
18     }
19     
20     @Override
21     public void undo() {
22         gd.down();
23     }
24 }

 1 //LightOffCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.Light;
 5 
 6 public class LightOffCommand implements Command {
 7     Light light;
 8     
 9     public LightOffCommand(Light light)
10     {
11         this.light = light;
12     }
13     
14     @Override
15     public void execute() 
16     {
17         light.off();
18     }
19     
20     @Override
21     public void undo() {
22         light.on();
23     }
24 }

 1 //LightOnCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.Light;
 5 
 6 public class LightOnCommand implements Command {
 7 
 8     Light light;
 9     
10     public LightOnCommand(Light light)
11     {
12         this.light = light;
13     }
14     
15     @Override
16     public void execute() 
17     {
18         light.on();
19     }
20     
21     @Override
22     public void undo() {
23         light.off();
24     }
25 }

 1 //NoCommand.java
 2 package RemoteControl.Command;
 3 
 4 public class NoCommand implements Command{
 5     public void execute()
 6     {}
 7     
 8     public void undo() 
 9     {}
10 }

 1 //StereoOffCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.Stereo;
 5 
 6 public class StereoOffCommand implements Command {
 7     Stereo stereo;
 8     
 9     public StereoOffCommand(Stereo stereo)
10     {
11         this.stereo = stereo;
12     }
13     
14     public void execute()
15     {
16         stereo.off();
17     }
18     
19     @Override
20     public void undo() {
21         stereo.on();
22     }
23 }

 1 //StereoOnWithCDCommand.java
 2 package RemoteControl.Command;
 3 
 4 import RemoteControl.device.Stereo;
 5 
 6 public class StereoOnWithCDCommand implements Command {
 7     Stereo stereo;
 8     
 9     public StereoOnWithCDCommand(Stereo stereo)
10     {
11         this.stereo = stereo;
12     }
13     
14     public void execute()
15     {
16         stereo.on();
17         stereo.setCD();
18         stereo.setVolume(11);
19     }
20     
21     @Override
22     public void undo() {
23         stereo.off();
24     }
25 }

(3) 实现Invoker类：

 1 //RemoteControl.java
 2 package RemoteControl;
 3 
 4 import RemoteControl.Command.Command;
 5 import RemoteControl.Command.NoCommand;
 6 
 7 public class RemoteControl {
 8     Command[] onCommands;
 9     Command[] offCommands;
10     Command undoCommand;
11      
12     public RemoteControl(){
13         onCommands = new Command[7];
14         offCommands = new Command[7];
15         
16         Command noCommand = new NoCommand();
17         for(int i=0; i<7; i++)
18         {
19             onCommands[i] = noCommand;
20             offCommands[i] = noCommand;
21         }
22         undoCommand = noCommand;
23     }
24     
25     public void setCommand(int slot, Command onCommand, Command offCommand)
26     {
27         onCommands[slot] = onCommand;
28         offCommands[slot] = offCommand;
29     }
30     
31     public void onButtonWasPushed(int slot)
32     {
33         onCommands[slot].execute();
34         undoCommand = onCommands[slot];
35     }
36     
37     public void offButtonWasPushed(int slot)
38     {
39         offCommands[slot].execute();
40         undoCommand = offCommands[slot];
41     }
42     
43     public void undoButtonWasPushed()
44     {
45         undoCommand.undo();
46     }
47     
48     public String toString()
49     {
50         StringBuffer stringBuff = new StringBuffer();
51         stringBuff.append("\n-------- Remote Control --------\n");
52         for(int i = 0; i < onCommands.length; i++)
53         {
54             stringBuff.append("[slot " + i + "] " + onCommands[i].getClass().getName()
55                     + "    " + offCommands[i].getClass().getName() + "\n");
56         }
57         return stringBuff.toString();
58     }
59 
60 }

 1 //RemoteControlTest.java
 2 package RemoteControl;
 3 
 4 import RemoteControl.Command.CeilingFanOffCommand;
 5 import RemoteControl.Command.CeilingFanOnCommand;
 6 import RemoteControl.Command.GarageDoorDownCommand;
 7 import RemoteControl.Command.GarageDoorUpCommand;
 8 import RemoteControl.Command.LightOffCommand;
 9 import RemoteControl.Command.LightOnCommand;
10 import RemoteControl.Command.StereoOffCommand;
11 import RemoteControl.Command.StereoOnWithCDCommand;
12 import RemoteControl.device.CeilingFan;
13 import RemoteControl.device.GarageDoor;
14 import RemoteControl.device.Light;
15 import RemoteControl.device.Stereo;
16 
17 public class RemoteControlTest {
18     public static void main(String[] args)
19     {
20         RemoteControl remoteControl = new RemoteControl();
21         
22         Light livingRoomLight = new Light("Living Room");
23         Light kitchenLight = new Light("Kitchen");
24         CeilingFan ceilingFan = new CeilingFan("Living Room");
25         GarageDoor garageDoor = new GarageDoor("");
26         Stereo stereo = new Stereo("Living Room");
27         
28         LightOnCommand lightRoomLightOn = new LightOnCommand(livingRoomLight);
29         LightOffCommand lightRoomLightOff = new LightOffCommand(livingRoomLight);
30         
31         LightOnCommand kitchenLightOn = new LightOnCommand(kitchenLight);
32         LightOffCommand kitchenLightOff = new LightOffCommand(kitchenLight);
33         
34         CeilingFanOnCommand ceilingFanOn = new CeilingFanOnCommand(ceilingFan);
35         CeilingFanOffCommand ceilingFanOff = new CeilingFanOffCommand(ceilingFan);
36         
37         GarageDoorUpCommand garageDoorUp = new GarageDoorUpCommand(garageDoor);
38         GarageDoorDownCommand garageDoorDown = new GarageDoorDownCommand(garageDoor);
39         
40         StereoOnWithCDCommand stereoOnWithCD = new StereoOnWithCDCommand(stereo);
41         StereoOffCommand stereoOff = new StereoOffCommand(stereo);
42         
43         remoteControl.setCommand(0, lightRoomLightOn, lightRoomLightOff);
44         remoteControl.setCommand(1, kitchenLightOn, kitchenLightOff);
45         remoteControl.setCommand(2, ceilingFanOn, ceilingFanOff);
46         remoteControl.setCommand(3, garageDoorUp, garageDoorDown);
47         
48         System.out.println(remoteControl);
49         
50         remoteControl.onButtonWasPushed(0);
51         remoteControl.offButtonWasPushed(0);
52         remoteControl.onButtonWasPushed(1);
53         remoteControl.offButtonWasPushed(1);
54         remoteControl.onButtonWasPushed(2);
55         remoteControl.offButtonWasPushed(2);
56         remoteControl.onButtonWasPushed(3);
57         remoteControl.offButtonWasPushed(3);
58         remoteControl.undoButtonWasPushed();
59     }
60 }

实现类图：