[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：

 //CeilingFan.java
 package RemoteControl.device;

 public class CeilingFan {
     String name;
     public CeilingFan(String str)
     {
         name = str;
     }

     public void on()
     {
         System.out.println(name + "CeilingFan On");
     }

     public void off()
     {
         System.out.println(name + "CeilingFan Off");
     }
 }

 //GarageDoor.java
 package RemoteControl.device;

 public class GarageDoor {
     String name;
     public GarageDoor(String str)
     {
         name = str;
     }

     public void up()
     {
         System.out.println(name + "GarageDoor On");
     }

     public void down()
     {
         System.out.println(name + "GarageDoor Off");
     }
 }

 //Light.java
 package RemoteControl.device;

 public class Light {
     String name;
     public Light(String str)
     {
         name = str;
     }

     public void on()
     {
         System.out.println(name + "Light On");
     }

     public void off()
     {
         System.out.println(name + "Light Off");
     }
 }

 //Stereo.java
 package RemoteControl.device;

 public class Stereo {
     String name;
     public Stereo(String str)
     {
         name = str;
     }

     public void on()
     {
         System.out.println(name + "Stereo On");
     }

     public void off()
     {
         System.out.println(name + "Stereo Off");
     }

     public void setCD()
     {
         System.out.println(name + "Stereo setCD");
     }

     public void setVolume(int num)
     {
         System.out.println(name + "Stereo setVolume:" + num);
     }
 }

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

 //CeilingFanOffCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.CeilingFan;

 public class CeilingFanOffCommand implements Command{
     CeilingFan cf;

     public CeilingFanOffCommand(CeilingFan cf)
     {
         this.cf = cf;
     }

     @Override
     public void execute()
     {
         cf.off();
     }

     @Override
     public void undo() {
         cf.on();
     }

 }

 //CeilingFanOnCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.CeilingFan;

 public class CeilingFanOnCommand implements Command{
     CeilingFan cf;

     public CeilingFanOnCommand(CeilingFan cf)
     {
         this.cf = cf;
     }

     @Override
     public void execute()
     {
         cf.on();
     }

     @Override
     public void undo() {
         cf.off();
     }
 }

 //Command.java
 package RemoteControl.Command;

 public interface Command {
     public void execute();
     public void undo();
 }

 //GarageDoorDownCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.GarageDoor;

 public class GarageDoorDownCommand implements Command {
     GarageDoor gd;

     public GarageDoorDownCommand(GarageDoor gd)
     {
         this.gd = gd;
     }

     @Override
     public void execute()
     {
         gd.down();
     }

     @Override
     public void undo() {
         gd.up();
     }
 }

 //GarageDoorUpCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.GarageDoor;

 public class GarageDoorUpCommand implements Command {
     GarageDoor gd;

     public GarageDoorUpCommand(GarageDoor gd)
     {
         this.gd = gd;
     }

     @Override
     public void execute()
     {
         gd.up();
     }

     @Override
     public void undo() {
         gd.down();
     }
 }

 //LightOffCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.Light;

 public class LightOffCommand implements Command {
     Light light;

     public LightOffCommand(Light light)
     {
         this.light = light;
     }

     @Override
     public void execute()
     {
         light.off();
     }

     @Override
     public void undo() {
         light.on();
     }
 }

 //LightOnCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.Light;

 public class LightOnCommand implements Command {

     Light light;

     public LightOnCommand(Light light)
     {
         this.light = light;
     }

     @Override
     public void execute()
     {
         light.on();
     }

     @Override
     public void undo() {
         light.off();
     }
 }

 //NoCommand.java
 package RemoteControl.Command;

 public class NoCommand implements Command{
     public void execute()
     {}

     public void undo()
     {}
 }

 //StereoOffCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.Stereo;

 public class StereoOffCommand implements Command {
     Stereo stereo;

     public StereoOffCommand(Stereo stereo)
     {
         this.stereo = stereo;
     }

     public void execute()
     {
         stereo.off();
     }

     @Override
     public void undo() {
         stereo.on();
     }
 }

 //StereoOnWithCDCommand.java
 package RemoteControl.Command;

 import RemoteControl.device.Stereo;

 public class StereoOnWithCDCommand implements Command {
     Stereo stereo;

     public StereoOnWithCDCommand(Stereo stereo)
     {
         this.stereo = stereo;
     }

     public void execute()
     {
         stereo.on();
         stereo.setCD();
         stereo.setVolume(11);
     }

     @Override
     public void undo() {
         stereo.off();
     }
 }

(3) 实现Invoker类：

 //RemoteControl.java
 package RemoteControl;

 import RemoteControl.Command.Command;
 import RemoteControl.Command.NoCommand;

 public class RemoteControl {
     Command[] onCommands;
     Command[] offCommands;
     Command undoCommand;

     public RemoteControl(){
         onCommands = new Command[7];
         offCommands = new Command[7];

         Command noCommand = new NoCommand();
         for(int i=0; i<7; i++)
         {
             onCommands[i] = noCommand;
             offCommands[i] = noCommand;
         }
         undoCommand = noCommand;
     }

     public void setCommand(int slot, Command onCommand, Command offCommand)
     {
         onCommands[slot] = onCommand;
         offCommands[slot] = offCommand;
     }

     public void onButtonWasPushed(int slot)
     {
         onCommands[slot].execute();
         undoCommand = onCommands[slot];
     }

     public void offButtonWasPushed(int slot)
     {
         offCommands[slot].execute();
         undoCommand = offCommands[slot];
     }

     public void undoButtonWasPushed()
     {
         undoCommand.undo();
     }

     public String toString()
     {
         StringBuffer stringBuff = new StringBuffer();
         stringBuff.append("\n-------- Remote Control --------\n");
         for(int i = 0; i < onCommands.length; i++)
         {
             stringBuff.append("[slot " + i + "] " + onCommands[i].getClass().getName()
                     + "    " + offCommands[i].getClass().getName() + "\n");
         }
         return stringBuff.toString();
     }

 }

 //RemoteControlTest.java
 package RemoteControl;

 import RemoteControl.Command.CeilingFanOffCommand;
 import RemoteControl.Command.CeilingFanOnCommand;
 import RemoteControl.Command.GarageDoorDownCommand;
 import RemoteControl.Command.GarageDoorUpCommand;
 import RemoteControl.Command.LightOffCommand;
 import RemoteControl.Command.LightOnCommand;
 import RemoteControl.Command.StereoOffCommand;
 import RemoteControl.Command.StereoOnWithCDCommand;
 import RemoteControl.device.CeilingFan;
 import RemoteControl.device.GarageDoor;
 import RemoteControl.device.Light;
 import RemoteControl.device.Stereo;

 public class RemoteControlTest {
     public static void main(String[] args)
     {
         RemoteControl remoteControl = new RemoteControl();

         Light livingRoomLight = new Light("Living Room");
         Light kitchenLight = new Light("Kitchen");
         CeilingFan ceilingFan = new CeilingFan("Living Room");
         GarageDoor garageDoor = new GarageDoor("");
         Stereo stereo = new Stereo("Living Room");

         LightOnCommand lightRoomLightOn = new LightOnCommand(livingRoomLight);
         LightOffCommand lightRoomLightOff = new LightOffCommand(livingRoomLight);

         LightOnCommand kitchenLightOn = new LightOnCommand(kitchenLight);
         LightOffCommand kitchenLightOff = new LightOffCommand(kitchenLight);

         CeilingFanOnCommand ceilingFanOn = new CeilingFanOnCommand(ceilingFan);
         CeilingFanOffCommand ceilingFanOff = new CeilingFanOffCommand(ceilingFan);

         GarageDoorUpCommand garageDoorUp = new GarageDoorUpCommand(garageDoor);
         GarageDoorDownCommand garageDoorDown = new GarageDoorDownCommand(garageDoor);

         StereoOnWithCDCommand stereoOnWithCD = new StereoOnWithCDCommand(stereo);
         StereoOffCommand stereoOff = new StereoOffCommand(stereo);

         remoteControl.setCommand(0, lightRoomLightOn, lightRoomLightOff);
         remoteControl.setCommand(1, kitchenLightOn, kitchenLightOff);
         remoteControl.setCommand(2, ceilingFanOn, ceilingFanOff);
         remoteControl.setCommand(3, garageDoorUp, garageDoorDown);

         System.out.println(remoteControl);

         remoteControl.onButtonWasPushed(0);
         remoteControl.offButtonWasPushed(0);
         remoteControl.onButtonWasPushed(1);
         remoteControl.offButtonWasPushed(1);
         remoteControl.onButtonWasPushed(2);
         remoteControl.offButtonWasPushed(2);
         remoteControl.onButtonWasPushed(3);
         remoteControl.offButtonWasPushed(3);
         remoteControl.undoButtonWasPushed();
     }
 }

实现类图：