6. 커맨드(Command) 패턴 - Head First Design Patterns

커맨드 패턴 정의 ) 커맨드 패턴을 이용하면 요구사항을 객체로 캡슐화 할수 있으며, 매개변수를 써서 여러가지 다른 요구 사항을 집어 넣을수 있다. 또한, 요청 내역을 큐에 저장하거나 로그를 기록하여, 작업 취소 기능도 넣을수 있다.

 

커맨트 패턴은 일련의 행동을 특정 리시버 하고 연결 시킴으로써 요구 사항을 캡슐화 시킨다.

요청을 하는 객체와 그 요청을 수행하는 객체를 분리시키고 싶다면 커맨드 패턴을 사용하면 된다.

 

 

커맨드 패턴 : 클래스 다이어그램

---

 

Remote Control 예제

 

public class LightOnCommand implements Command {
	Light light;

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

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

public class RemoteControl {
	Command[] onCommands;	// on 버튼들 모아놓는 배열
	Command[] offCommands;	// off 버튼들 모아놓는 배열
 
	public RemoteControl() {
		onCommands = new Command[7];
		offCommands = new Command[7];
 
		Command noCommand = new NoCommand();
		for (int i = 0; i < 7; i++) {
			onCommands[i] = noCommand;	// 일단 초기화를 커맨드가 없는 noCommand 객체 넣음.
			offCommands[i] = noCommand; // 일단 초기화를 커맨드가 없는 noCommand 객체 넣음.
		}
	}
  
	public void setCommand(int slot, Command onCommand, Command offCommand) {
		onCommands[slot] = onCommand;
		offCommands[slot] = offCommand;
	}
 
	public void onButtonWasPushed(int slot) { // slot에 해당하는 객체 on 실행(execute)
		onCommands[slot].execute();
	}
 
	public void offButtonWasPushed(int slot) { // slot에 해당하는 객체 off 실행(execute)
		offCommands[slot].execute();
	}
  
	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();
	}
}

public class RemoteLoader {
 
	public static void main(String[] args) {
		RemoteControl remoteControl = new RemoteControl(); //리모컨 객체 생성
 //living room에 있는 Light 객체 생성
		Light livingRoomLight = new Light("Living Room");
 //on,off커맨드에 Light 위치를 넘겨줌.
		LightOnCommand livingRoomLightOn = 
				new LightOnCommand(livingRoomLight);
		LightOffCommand livingRoomLightOff = 
				new LightOffCommand(livingRoomLight);
 //on,off command 등록
		remoteControl.setCommand(0, livingRoomLightOn, livingRoomLightOff);
  
		System.out.println(remoteControl);
 
		remoteControl.onButtonWasPushed(0);
		remoteControl.offButtonWasPushed(0);
	}
}

출력 )  [slot 0] package.LightOnCommand         package.LightOffCommand

         ( noCommand ..생략 )

         Living Room light is on

         Living Room light is off

 

 

 

간단한 리모컨 : 클래스 다이어그램

리모컨 : 클래스 다이어그램

 

---

 

리모컨에 Undo() 기능 추가하기.

 

public interface Command{
	public void execute();
    	 public void undo();	// <<-- undo만 추가해주면 됨! 
  }

//LightOnCommand

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

public void undo(){
	light.off(); // on -> off / off -> on
}

public class RemoteControlWithUndo {
	Command[] onCommands;
	Command[] offCommands;
	Command undoCommand;	// new!
 
	public RemoteControlWithUndo() {
		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;	// new!
	}
  
	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];		// new!
	}
 
	public void offButtonWasPushed(int slot) {
		offCommands[slot].execute();
		undoCommand = offCommands[slot];	// new!
	}
 
	public void undoButtonWasPushed() {		// new!
		undoCommand.undo();					
	}
   //toString() 생략.
}

 

 

party mode

public class MacroCommand implements Command{
	Command[] commands;
    
    public MacroCommand( Command[] commands){
    	this.commands = commands;
    }
    
    public void execute(){
    	for(int i=0; i< commands.length; i++){
        	commands[i].execute();
       	}
   }

//Macro 등록.

Command[] partyOn = {lightOn, stereoOn, tvOn, hottubOn};
Command[] partyOff = {lightOff, stereoOff, tvOff, hottubOff};

MacroCommand partyOnMacro = new MacroCommand(partyOn);
MacroCommand partyOffMacro = new MacroCommand(partyOff);

---