设计模式 7 —— 命令模式

设计模式目录：

概述

第1部分问题引入

第2部分定义和实现

第3部分使用宏命令

第1部分问题引入

首先看下，下面的要求：

实现命令接口

首先，让说有的命令对象实现相同的包含一个方法的接口。

1 /**
2  * 命令接口
3  * @ClassName: Command
4  * @author Xingle
5  * @date 2014-9-11 上午10:13:46
6  */
7 public interface Command {
8     public void execute();
9 }

实现一个打开电灯的命令

在实现打开电灯或者关闭电灯之前，先看下灯的类

 1 public class Light {
 2     
 3     public Light(){} 
 4     
 5     //开灯
 6     public void on(){
 7         System.out.println("Light is on");
 8     }
 9 
10     //关灯
11     public void off(){
12         System.out.println("Light is off");
13     }
14 }

接着开灯以及关灯命令：

 1 /**
 2  * 实现一个开灯命令
 3  * @ClassName: LightOnCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午10:25:19
 7  */
 8 public class LightOnCommand implements Command{
 9     
10     Light light;
11     
12     public LightOnCommand(Light light){
13         this.light = light;
14     }
15 
16     @Override
17     public void execute() {
18         light.on();
19     }
20 
21 }

 1 /**
 2  * 实现一个关灯命令
 3  * @ClassName: LightOffCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午10:55:35
 7  */
 8 public class LightOffCommand implements Command{
 9 
10     Light light;
11     
12     public LightOffCommand(Light light){
13         this.light = light;
14     };
15     
16     @Override
17     public void execute() {
18         light.off();        
19     }
20 
21 }

使用命令对象

假设我们有一个遥控器，它只有一个按钮和对应的插槽，可以控制一个装置：

 1 //
 2 //This is the invoker
 3 //
 4 public class SimpleRemoteControl {
 5     //一个插槽持有命令，控制着一个装置
 6     Command slot;
 7     
 8     public SimpleRemoteControl(){};
 9     
10     //这个方法用来设置插槽控制的命令。如果客户想要改变遥控器按钮的行为，可以多次调用这个方法
11     public void setCommand(Command command){
12         slot = command;
13     }
14     //当按下按钮时，这个方法就会被调用，使得当前命令衔接插槽，并调用它的execute()方法
15     public void buttonWasPressed(){
16         slot.execute();
17     }
18 }

下面再多加一个控制车库门的命令，车库门以及命令如下：

 1 /**
 2  * 车库门
 3  * @ClassName: GarageDoor 
 4  * @author Xingle
 5  * @date 2014-9-11 上午10:53:15
 6  */
 7 public class GarageDoor {
 8     public GarageDoor() {
 9     }
10 
11     public void up() {
12         System.out.println("Garage Door is Open");
13     }
14 
15     public void down() {
16         System.out.println("Garage Door is Closed");
17     }
18 
19     public void stop() {
20         System.out.println("Garage Door is Stopped");
21     }
22 
23     public void lightOn() {
24         System.out.println("Garage light is on");
25     }
26 
27     public void lightOff() {
28         System.out.println("Garage light is off");
29     }
30 }

 1 /**
 2  * 开车库门命令
 3  * @ClassName: GarageDoorOpenCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午10:53:52
 7  */
 8 public class GarageDoorOpenCommand implements Command{
 9 
10     GarageDoor garageDoor;
11     
12     public GarageDoorOpenCommand(GarageDoor garageDoor) {
13         this.garageDoor = garageDoor;
14     }
15     
16     @Override
17     public void execute() {
18         garageDoor.up();
19     }
20 }

遥控器使用的简单测试：

 1 /**
 2  * 遥控器的测试程序
 3  * @ClassName: RemoteControlTest
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午10:57:38
 7  */
 8 public class RemoteControlTest {
 9     public static void main(String[] args){
10         //遥控器就是调用者，会传入一个命令对象，可以用来发出请求
11         SimpleRemoteControl remote = new SimpleRemoteControl();
12         
13         //创建了一个电灯对象，也就是请求的接受者
14         Light light = new Light();
15         GarageDoor garageDoor = new GarageDoor();
16         //创建一个命令，然后将接受者传给它
17         LightOnCommand lightOn = new LightOnCommand(light);
18         GarageDoorOpenCommand garageOpen = new GarageDoorOpenCommand(garageDoor);
19 
20         //把命令传给调用者
21         remote.setCommand(lightOn);
22         //模拟按下按钮
23         remote.buttonWasPressed();
24         
25         remote.setCommand(garageOpen);
26         remote.buttonWasPressed();
27     }
28 }

执行结果：

第2部分定义和实现

命令模式 将“请求”封装成对象，以便使用不用的请求、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。

　　一个命令对象通过在特定接受者上绑定一组动作来封装一个请求。要达到这一点，命令对象将动作和接受者包进对象中。这个对象只暴露一个execute() 方法，当此方法被调用的时候，接收者就会进行这些动作。从外面看，其他对象不知道究竟哪个接收者进行了哪些动作，只知道如果调用execute() 方法，请求的目的就能达到。

将命令指定到插槽

　　将遥控器的每个插槽，对应到一个命令，这样就让遥控器变成“调用者”。当按下按钮，相应的命令对象的execute() 方法就会被调用，其结果是，接收者（例如：电灯、音响，电扇）的动作被调用。

实现遥控器

 1 /**
 2  * 带有撤销的遥控器
 3  * @ClassName: RemoteControlWithUndo 
 4  * @author Xingle
 5  * @date 2014-9-11 下午12:18:47
 6  */
 7 public class RemoteControlWithUndo {
 8 
 9     Command[] onCommands;
10     Command[] offCommands;
11     //前一个命令将被记录在这里
12     Command undoCommand;
13 
14     public RemoteControlWithUndo() {
15         //遥控器要处理7个开与关的命令，使用相应数组记录这些命令
16         onCommands = new Command[7];
17         offCommands = new Command[7];
18         //空对象
19         Command noCommand = new NoCommand();
20         
21         for (int i = 0; i < 7; i++) {
22             onCommands[i] = noCommand;
23             offCommands[i] = noCommand;
24         }
25         undoCommand = noCommand;
26     }
27 
28     public void setCommand(int slot, Command onCommand, Command offCommand) {
29         onCommands[slot] = onCommand;
30         offCommands[slot] = offCommand;
31     }
32 
33     public void onButtonWasPushed(int slot) {
34         onCommands[slot].execute();
35         undoCommand = onCommands[slot];
36     }
37 
38     public void offButtonWasPushed(int slot) {
39         offCommands[slot].execute();
40         undoCommand = offCommands[slot];
41     }
42 
43     public void undoButtonWasPushed() {
44         undoCommand.undo();
45     }
46 
47     public String toString() {
48         StringBuffer stringBuff = new StringBuffer();
49         stringBuff.append("
------ Remote Control -------
");
50         for (int i = 0; i < onCommands.length; i++) {
51             stringBuff.append("[slot " + i + "] "
52                     + onCommands[i].getClass().getName() + "    "
53                     + offCommands[i].getClass().getName() + "
");
54         }
55         stringBuff.append("[undo] " + undoCommand.getClass().getName() + "
");
56         return stringBuff.toString();
57     }
58 
59 }

命令接口

1 public interface Command {
2     
3     public void execute();
4     
5     //撤销操作
6     public void undo();
7 
8 }

灯的类

 1 /**
 2  * 灯
 3  * @ClassName: Light
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午11:52:57
 7  */
 8 public class Light {
 9     String location = "";
10 
11     public Light(String location) {
12         this.location = location;
13     }
14 
15     public void on() {
16         System.out.println(location + " light is on");
17     }
18 
19     public void off() {
20         System.out.println(location + " light is off");
21     }
22 }

实现命令

 1 /**
 2  * 开灯
 3  * @ClassName: LightOnCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午11:52:18
 7  */
 8 public class LightOnCommand implements Command{
 9     Light light ;
10 
11     public LightOnCommand(Light light){
12         this.light = light;
13     }
14     @Override
15     public void execute() {
16         light.on();
17     }
18     @Override
19     public void undo() {
20         light.off();
21     }
22 
23 }

 1 /**
 2  * 关灯
 3  * @ClassName: LightOffCommand 
 4  * @author Xingle
 5  * @date 2014-9-11 下午12:00:05
 6  */
 7 public class LightOffCommand implements Command {
 8 
 9     Light light;
10 
11     public LightOffCommand(Light light) {
12         this.light = light;
13     }
14 
15     @Override
16     public void execute() {
17         light.off();
18     }
19     
20     @Override
21     public void undo() {
22         light.on();
23     }
24 
25 }

音响

 1 /**
 2  * 音响
 3  * @ClassName: Stereo
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午11:54:46
 7  */
 8 public class Stereo {
 9     
10     String location;
11 
12     public Stereo(String location) {
13         this.location = location;
14     }
15 
16     public void on() {
17         System.out.println(location + " stereo is on");
18     }
19 
20     public void off() {
21         System.out.println(location + " stereo is off");
22     }
23 
24     public void setCD() {
25         System.out.println(location + " stereo is set for CD input");
26     }
27 
28     public void setDVD() {
29         System.out.println(location + " stereo is set for DVD input");
30     }
31 
32     public void setRadio() {
33         System.out.println(location + " stereo is set for Radio");
34     }
35 
36     public void setVolume(int volume) {
37         System.out.println(location + " Stereo volume set to " + volume);
38     }
39 
40 }

音响的命令操作

 1 /**
 2  * 开音响
 3  * @ClassName: StereoOnWithCDCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 上午11:54:19
 7  */
 8 public class StereoOnWithCDCommand implements Command{
 9 
10     Stereo stereo;
11     
12     public StereoOnWithCDCommand(Stereo stereo) {
13         this.stereo = stereo;
14     }
15  
16     @Override
17     public void execute() {
18         stereo.on();
19     }
20 
21     @Override
22     public void undo() {
23         stereo.off();
24     }
25 
26 }

 1 /**
 2  * 关音响
 3  * @ClassName: StereoOffCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午12:03:02
 7  */
 8 public class StereoOffCommand implements Command{
 9     Stereo stereo;
10     
11     public StereoOffCommand(Stereo stereo) {
12         this.stereo = stereo;
13     }
14 
15     @Override
16     public void execute() {
17         stereo.off();
18     }
19 
20     @Override
21     public void undo() {
22         stereo.on();
23     }
24 
25 }

吊扇

 1 /**
 2  * 吊扇
 3  * 
 4  * @ClassName: CeilingFan 
 5  * @author Xingle
 6  * @date 2014-9-11 下午12:36:04
 7  */
 8 public class CeilingFan {
 9 
10     
11     public static final int HIGH = 3;
12     public static final int MEDIUM = 2;
13     public static final int LOW = 1;
14     public static final int OFF = 0;
15     String location;
16     int speed;
17 
18     public CeilingFan(String location) {
19         this.location = location;
20         speed = OFF;
21     }
22 
23     //高速
24     public void high() {
25         speed = HIGH;
26         System.out.println(location + " ceiling fan is on high");
27     }
28     //中速
29     public void medium() {
30         speed = MEDIUM;
31         System.out.println(location + " ceiling fan is on medium");
32     }
33     //低速
34     public void low() {
35         speed = LOW;
36         System.out.println(location + " ceiling fan is on low");
37     }
38     //关闭
39     public void off() {
40         speed = OFF;
41         System.out.println(location + " ceiling fan is off");
42     }
43 
44     public int getSpeed() {
45         return speed;
46     }
47 
48 }

电扇的三个命令，分别把电扇开到高速，中速，和低速

 1 /**
 2  * 开电扇到高速
 3  * @ClassName: CeilingFanHighCommand 
 4  * @author Xingle
 5  * @date 2014-9-11 下午12:37:20
 6  */
 7 public class CeilingFanHighCommand implements Command {
 8 
 9     CeilingFan ceilingFan;
10     int prevSpeed;
11 
12     public CeilingFanHighCommand(CeilingFan ceilingFan) {
13         this.ceilingFan = ceilingFan;
14     }
15 
16     @Override
17     public void execute() {
18         prevSpeed = ceilingFan.getSpeed();
19         ceilingFan.high();
20     }
21 
22     @Override
23     public void undo() {
24         if (prevSpeed == CeilingFan.HIGH) {
25             ceilingFan.high();
26         } else if (prevSpeed == CeilingFan.MEDIUM) {
27             ceilingFan.medium();
28         } else if (prevSpeed == CeilingFan.LOW) {
29             ceilingFan.low();
30         } else if (prevSpeed == CeilingFan.OFF) {
31             ceilingFan.off();
32         }
33     }
34 
35 }

 1 /**
 2  * 开电扇到中速
 3  * @ClassName: CeilingFanMediumCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午12:39:57
 7  */
 8 public class CeilingFanMediumCommand implements Command{
 9     CeilingFan ceilingFan;
10     int prevSpeed;
11 
12     public CeilingFanMediumCommand(CeilingFan ceilingFan) {
13         this.ceilingFan = ceilingFan;
14     }
15     @Override
16     public void execute() {
17         prevSpeed = ceilingFan.getSpeed();
18         ceilingFan.medium();
19     }
20 
21     @Override
22     public void undo() {
23         if (prevSpeed == CeilingFan.HIGH) {
24             ceilingFan.high();
25         } else if (prevSpeed == CeilingFan.MEDIUM) {
26             ceilingFan.medium();
27         } else if (prevSpeed == CeilingFan.LOW) {
28             ceilingFan.low();
29         } else if (prevSpeed == CeilingFan.OFF) {
30             ceilingFan.off();
31         }
32     }
33 }

 1 /**
 2  * 开电扇到低速
 3  * @ClassName: CeilingFanLowCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午12:38:25
 7  */
 8 public class CeilingFanLowCommand implements Command{
 9     
10     CeilingFan ceilingFan;
11     int prevSpeed;
12   
13     public CeilingFanLowCommand(CeilingFan ceilingFan) {
14         this.ceilingFan = ceilingFan;
15     }
16 
17     @Override
18     public void execute() {
19         prevSpeed = ceilingFan.getSpeed();
20         ceilingFan.low();
21     }
22 
23     @Override
24     public void undo() {
25         if (prevSpeed == CeilingFan.HIGH) {
26             ceilingFan.high();
27         } else if (prevSpeed == CeilingFan.MEDIUM) {
28             ceilingFan.medium();
29         } else if (prevSpeed == CeilingFan.LOW) {
30             ceilingFan.low();
31         } else if (prevSpeed == CeilingFan.OFF) {
32             ceilingFan.off();
33         }
34     }
35 
36 }

关电扇命令

 1 /**
 2  * 关电扇
 3  * @ClassName: CeilingFanOffCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午12:45:18
 7  */
 8 public class CeilingFanOffCommand implements Command{
 9     
10     CeilingFan ceilingFan;
11     int prevSpeed;
12   
13     public CeilingFanOffCommand(CeilingFan ceilingFan) {
14         this.ceilingFan = ceilingFan;
15     }
16 
17     @Override
18     public void execute() {
19         prevSpeed = ceilingFan.getSpeed();
20         ceilingFan.off();
21     }
22 
23     @Override
24     public void undo() {
25         if (prevSpeed == CeilingFan.HIGH) {
26             ceilingFan.high();
27         } else if (prevSpeed == CeilingFan.MEDIUM) {
28             ceilingFan.medium();
29         } else if (prevSpeed == CeilingFan.LOW) {
30             ceilingFan.low();
31         } else if (prevSpeed == CeilingFan.OFF) {
32             ceilingFan.off();
33         }
34     }
35 
36 }

测试遥控器

 1 /**
 2  * 测试程序
 3  * 
 4  * @ClassName: RemoteLoader 
 5  * @author Xingle
 6  * @date 2014-9-11 上午11:57:26
 7  */
 8 public class RemoteLoader {
 9     public static void main(String[] args) {
10     
11         RemoteControlWithUndo remoteControl = new RemoteControlWithUndo();
12 
13         Light livingRoomLight = new Light("Living Room");
14 
15         CeilingFan ceilingFan = new CeilingFan("ww Room");
16         
17         
18         
19         LightOnCommand livingRoomLightOn = new LightOnCommand(livingRoomLight);
20         LightOffCommand livingRoomLightOff = new LightOffCommand(livingRoomLight);
21         
22         CeilingFanMediumCommand ceilingFanMedium = new CeilingFanMediumCommand(ceilingFan);
23         CeilingFanLowCommand ceilingFanLow = new CeilingFanLowCommand(ceilingFan);
24         CeilingFanHighCommand ceilingFanHigh = new CeilingFanHighCommand(ceilingFan);
25         CeilingFanOffCommand ceilingFanOff = new CeilingFanOffCommand(ceilingFan);
26 
27         //
28         remoteControl.setCommand(0, livingRoomLightOn, livingRoomLightOff);        
29         remoteControl.setCommand(1, ceilingFanMedium, ceilingFanOff);
30         remoteControl.setCommand(2, ceilingFanHigh, ceilingFanOff);
31 
32         remoteControl.onButtonWasPushed(0);
33         remoteControl.offButtonWasPushed(0);
34         System.out.println(remoteControl);
35         remoteControl.undoButtonWasPushed();
36     
37         remoteControl.onButtonWasPushed(1);//中速开
38         remoteControl.offButtonWasPushed(1);//关闭
39         System.out.println(remoteControl);
40         remoteControl.undoButtonWasPushed();//撤销，会回到中速
41         
42         remoteControl.onButtonWasPushed(2);//高度开
43         System.out.println(remoteControl);//
44         remoteControl.undoButtonWasPushed();//撤销，回到中速
45     }
46 
47 }

执行结果：

Living Room light is on
Living Room light is off

------ Remote Control -------
[slot 0] firsthead.command.remote.LightOnCommand firsthead.command.remote.LightOffCommand
[slot 1] firsthead.command.remote.CeilingFanMediumCommand firsthead.command.remote.CeilingFanOffCommand
[slot 2] firsthead.command.remote.CeilingFanHighCommand firsthead.command.remote.CeilingFanOffCommand
[slot 3] firsthead.command.remote.NoCommand firsthead.command.remote.NoCommand
[slot 4] firsthead.command.remote.NoCommand firsthead.command.remote.NoCommand
[slot 5] firsthead.command.remote.NoCommand firsthead.command.remote.NoCommand
[slot 6] firsthead.command.remote.NoCommand firsthead.command.remote.NoCommand
[undo] firsthead.command.remote.LightOffCommand

Living Room light is on
ww Room ceiling fan is on medium
ww Room ceiling fan is off

ww Room ceiling fan is on medium
ww Room ceiling fan is on high

ww Room ceiling fan is on medium

第3部分使用宏命令

宏命令(macro command), 即多个命令的组合操作。

 1 /**
 2  * 宏命令
 3  * @ClassName: MacroCommand
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午3:09:38
 7  */
 8 public class MacroCommand implements Command{
 9     
10     Command[] commands;
11      
12     public MacroCommand(Command[] commands) {
13         this.commands = commands;
14     }
15 
16     @Override
17     public void execute() {
18         for (int i = 0; i < commands.length; i++) {
19             commands[i].execute();
20         }
21     }
22 
23     @Override
24     public void undo() {
25         for (int i = commands.length -1; i >= 0; i--) {
26             commands[i].undo();
27         }
28     }
29 
30 }

 1 /**
 2  * 遥控
 3  * @ClassName: RemoteControl
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午3:04:43
 7  */
 8 public class RemoteControl {
 9     Command[] onCommands;
10     Command[] offCommands;
11     Command undoCommand;
12  
13     public RemoteControl() {
14         onCommands = new Command[7];
15         offCommands = new Command[7];
16  
17         Command noCommand = new NoCommand();
18         for(int i=0;i<7;i++) {
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         onCommands[slot] = onCommand;
27         offCommands[slot] = offCommand;
28     }
29  
30     public void onButtonWasPushed(int slot) {
31         onCommands[slot].execute();
32         undoCommand = onCommands[slot];
33     }
34  
35     public void offButtonWasPushed(int slot) {
36         offCommands[slot].execute();
37         undoCommand = offCommands[slot];
38     }
39 
40     public void undoButtonWasPushed() {
41         undoCommand.undo();
42     }
43  
44     public String toString() {
45         StringBuffer stringBuff = new StringBuffer();
46         stringBuff.append("
------ Remote Control -------
");
47         for (int i = 0; i < onCommands.length; i++) {
48             stringBuff.append("[slot " + i + "] " + onCommands[i].getClass().getName()
49                 + "    " + offCommands[i].getClass().getName() + "
");
50         }
51         stringBuff.append("[undo] " + undoCommand.getClass().getName() + "
");
52         return stringBuff.toString();
53     }
54 }

测试程序：

 1 /**
 2  * 带宏的测试程序
 3  * @ClassName: RemoteLoader
 4  * TODO
 5  * @author Xingle
 6  * @date 2014-9-11 下午3:04:18
 7  */
 8 public class RemoteLoader {
 9     public static void main(String[] args) {
10 
11         RemoteControl remoteControl = new RemoteControl();
12         Light light = new Light("Living Room");    
13         Stereo stereo = new Stereo("Living Room");
14          
15         LightOnCommand lightOn = new LightOnCommand(light);
16         StereoOnCommand stereoOn = new StereoOnCommand(stereo);
17         LightOffCommand lightOff = new LightOffCommand(light);
18         StereoOffCommand stereoOff = new StereoOffCommand(stereo);
19 
20         //一个数组记录开启命令
21         Command[] partyOn = { lightOn,  stereoOn};
22         //一个数组记录关闭命令
23         Command[] partyOff = { lightOff, stereoOff};
24   
25         /**
26          * 创建两个对应的宏持有它们
27          */
28         MacroCommand partyOnMacro = new MacroCommand(partyOn);
29         MacroCommand partyOffMacro = new MacroCommand(partyOff);
30  
31         //将宏命令指定给一个按钮
32         remoteControl.setCommand(0, partyOnMacro, partyOffMacro);
33   
34         System.out.println(remoteControl);
35         System.out.println("--- Pushing Macro On---");
36         remoteControl.onButtonWasPushed(0);
37         System.out.println("--- Pushing Macro Off---");
38         remoteControl.offButtonWasPushed(0);
39     }
40 }

执行结果：

------ Remote Control -------
[slot 0] firsthead.command.party.MacroCommand firsthead.command.party.MacroCommand
[slot 1] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[slot 2] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[slot 3] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[slot 4] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[slot 5] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[slot 6] firsthead.command.party.NoCommand firsthead.command.party.NoCommand
[undo] firsthead.command.party.NoCommand

--- Pushing Macro On---
Light is on
Living Room stereo is on
--- Pushing Macro Off---
Light is off
Living Room stereo is off

设计模式 7 —— 命令模式

第1部分 问题引入

第2部分 定义和实现

第3部分 使用宏命令

第1部分问题引入

第2部分定义和实现

第3部分使用宏命令