6. Command Pattern

6. Command Pattern (커맨드 패턴)

6.1 Command Pattern의 다이어그램

- 실제 기능을할 메소드를 가진 객체는 receiver 클래스입니다.

- command interface를 구현한 각 concreteCommand(구상커맨드클래스)들은 receiver들의 reference를 가졌고 receiver들의 메소드를 호출합니다.

- invoker class는 setCommand() 메소드를 이용해 concreteCommand들을 설정하고 execute() 메소드를 호출함으로서 receiver의 메소드를 호출합니다.

6.2 Simple RemoteControl

invoker, command, receiver가 어떻게 연결되는지 간단한 리모컨 예를통해 보여드릴게요.

- main class 1

- command interface 1

- concrete command class 1

- receiver 1

- invoker 1

총 5개의 클래스

6.2.1 reciever class

실제 원하는 기능 메소드를 가진 클래스입니다.

package receiver;
// receiver class
public class Light {
    public void on() {
        System.out.println("this is light!");
    }
}
 

6.2.2 command interface

구상 커맨드 클래스들이 구현해야하는 커맨드 인터페이스 입니다.

package command;
 
public interface Command {
    public void execute();
}
 

6.2.3 concrete command class

- 커맨드 인터페이스를 구현한 구상커맨드 클래스입니다.

- 각 구상커맨드 클래스의 execute()메소드와 receiver class의 기능 메소드가 연결됩니다.

- 구상커맨드 클래스는 연결하고자 하는 receiver의 reference를 가지고 있습니다.

package command;
import receiver.Light;
 
public class LightOnCommand implements Command {
    // receiver reference
    Light light;
    
    public LightOnCommand(Light light) {
        this.light = light;
    }
 
    @Override
    public void execute() {
        light.on();    // receiver 객체의 메소드를 호출
        
    }
    
}
 

6.2.4 invoker class

구상커맨드 클래스들을 설정하여 사용하는 클래스입니다.

package invoker;
import command.Command;
 
public class SimpleRemoteControl {
    Command slot;
    
    public void setCommand(Command command) {
        this.slot = command;
    }
    
    public void buttonWasPressed() {
        slot.execute();
    }
    
}
 

6.2.5 main class

test class입니다.

import command.LightOnCommand;
import invoker.SimpleRemoteControl;
import receiver.Light;
 
public class RemoteControlTest {
    public static void main(String args[]) {
        // invoker
        SimpleRemoteControl remote = new SimpleRemoteControl();
        
        // receiver
        Light light = new Light();
        
        // concrete command
        LightOnCommand lightOn = new LightOnCommand(light);
        
        // invoker set command
        remote.setCommand(lightOn);
        
        remote.buttonWasPressed();
    }
}
 

6.3 Remotecontrol

위의 simple remotecontol의 경우 하나의 command만 set가능합니다. 

하지만 invoker에 여러개의 command를 set하여 사용할 수 있도록 확장해보겠습니다.

6.3.1 receiver class

package receiver;
 
public class Light {
    String lightName;
    
    public Light(String lightName) {
        this.lightName = lightName;
    }
    
    public void on() {
        System.out.println(lightName+"불이 들어왔습니다.");
    }
    public void off() {
        System.out.println(lightName+"불이 꺼졌습니다.");
    }
}
 

package receiver;
 
public class Door {
    String doorName;
    
    public Door(String doorName) {
        this.doorName = doorName;
    }
    
    public void Open() {
        System.out.println(doorName+"문이 열렸습니다.");
    }
    
    public void close() {
        System.out.println(doorName+"문이 닫혔습니다.");
    }
}
 

6.3.2 command interface

package command;
 
public interface Command {
    public void execute();
}
 

6.3.3 concrete command calss

- 불을 켜는 커맨드

package command;
import receiver.Light;
 
public class LightOnCommand implements Command {
    Light light;
    
    public LightOnCommand(Light light) {
        this.light = light;
    }
    
    @Override
    public void execute() {
        light.on();
    }
 
}
 

- 불을 끄는 커맨드

package command;
import receiver.Light;
 
public class LightOffCommand implements Command {
    Light light;
    
    public LightOffCommand(Light light) {
        this.light = light;
    }
    
    @Override
    public void execute() {
        light.off();
    }
 
}
 

- 문을 여는 커맨드

package command;
import receiver.Door;
 
public class DoorOpenCommand implements Command {
    Door door;
    
    public DoorOpenCommand(Door door) {
        this.door = door;
    }
 
    @Override
    public void execute() {
        door.Open();
    }
    
}
 

- 문을 닫는 커맨드

package command;
import receiver.Door;
 
public class DoorCloseCommand implements Command {
    Door door;
    
    public DoorCloseCommand(Door door) {
        this.door = door;
    }
    
    @Override
    public void execute() {
        door.close();
    }
}
 

- NULL 커맨드 : invoker에 초기화 시킬 깡통 커맨드 클래스

package command;
 
public class NoCommand implements Command {
 
    @Override
    public void execute() {
        System.out.println("설정된 명령이 없습니다.");
    }
 
}
 

6.3.4 invoker class

package invoker;
import command.Command;
import command.NoCommand;
 
public class RemoteControl {
    Command[] onCommands;
    Command[] offCommands;
    public static int slotAmount = 4;
    
    public RemoteControl() {
        this.onCommands = new Command[slotAmount];
        this.offCommands = new Command[slotAmount];
        
        Command noCommand = new NoCommand();
        for(int i=0; i<slotAmount;i++) {
            onCommands[i] = noCommand;
            offCommands[i] = noCommand;
        }
    }
    
    public void setCommand(int slotNumber, Command onCommand, Command offCommand) {
        onCommands[slotNumber] = onCommand;
        offCommands[slotNumber] = offCommand;
    }
    
    public void onButtonWasPressed(int slotNumber) {
        onCommands[slotNumber].execute();
    }
    
    public void offButtonWasPressed(int slotNumber) {
        offCommands[slotNumber].execute();
    }
    
    
    @Override
    public String toString() {
        StringBuffer buffer = new StringBuffer();
        buffer.append("\n - RemoteControl's commands - \n");
        for(int i=0; i<onCommands.length; i++) {
            buffer.append("slot["+i+"] - "+"onCommand : "+onCommands[i].getClass().getName()+", offCommand : "+offCommands[i].getClass().getName()+"\n");
        }
        
        return buffer.toString();
    }
   
}
 

6.3.5 main class

import command.DoorCloseCommand;
import command.DoorOpenCommand;
import command.LightOffCommand;
import command.LightOnCommand;
import invoker.RemoteControl;
import receiver.Door;
import receiver.Light;
 
public class RemoteControlTest {
    public static void main(String[] args) {
        // invoker
        RemoteControl remoteControl = new RemoteControl();
        
        // receivers
        Light bathRoomLight = new Light("bathRoom");
        Light livingRoomLight = new Light("LivingRoom");
        
        // concrete commands
        LightOnCommand bathRoomLightOn = new LightOnCommand(bathRoomLight);
        LightOffCommand bathRoomLightOff = new LightOffCommand(bathRoomLight);
        LightOnCommand livingRoomLightOn = new LightOnCommand(livingRoomLight);
        LightOffCommand livingRoomLightOff = new LightOffCommand(livingRoomLight);
        
        // receivers
        Door garageDoor = new Door("garageDoor");
        Door houseDoor = new Door("houseDoor");
        
        // concrete commands
        DoorOpenCommand garageDoorOpen = new DoorOpenCommand(garageDoor);
        DoorCloseCommand garageDoorClose = new DoorCloseCommand(garageDoor);
        DoorOpenCommand houseDoorOpen = new DoorOpenCommand(houseDoor);
        DoorCloseCommand houseDoorClose = new DoorCloseCommand(houseDoor);
        
        // invoker set commands
        remoteControl.setCommand(0, bathRoomLightOn, bathRoomLightOff);
        remoteControl.setCommand(1, livingRoomLightOn, livingRoomLightOff);
        remoteControl.setCommand(2, garageDoorOpen, garageDoorClose);
        remoteControl.setCommand(3, houseDoorOpen, houseDoorClose);
        
        // test
        for(int i=0;i<remoteControl.slotAmount;i++) {
            remoteControl.onButtonWasPressed(i);
            remoteControl.offButtonWasPressed(i);
        }
        
        System.out.println(remoteControl.toString());
        
    }
}