템플릿 메서드 패턴 & 팩토리 메서드 패턴

 

'자바 객체 지향 디자인 패턴' 책을 구입하시길  추천드립니다.

책 구입을 원하시는분은 요기를 클릭하시면 됩니다.

하단의 내용은 제가 예전에 읽었던 내용을 요약 정리한 것입니다.

https://en.wikipedia.org/wiki/Template_method_pattern

1. 템플릿 메소드 패턴

 

동일한 기능을 상위 클래스에서 정의하면서 확장/변화가 필요한 부분만 서브클래스에서 구현하는 패턴

 

공통기능을 담당하는 추상클래스의 특정메소드에 (공통기능은 덤) 추상 메소드를 호출하는 코드를 넣어(hook,primitive메서드) 변화가 필요한 부분을 서브클래스에서 구현할 수 있게 해놓은것

 

 

 

하단과 같이 오티스 엘리베이터의 모터 클래스가 있다고 하자

 

public class OtisMotor {
	private Door door ;
	private MotorStatus motorStatus ;
	
	public OtisMotor(Door door) {
		this.door = door ;
		motorStatus = MotorStatus.STOPPED ;
	}	
	private void moveOtisMotor(Direction direction) {
		
	}
	public MotorStatus getMotorStatus() {
		return motorStatus;
	}
	private void setMotorStatus(MotorStatus motorStatus) {
		this.motorStatus = motorStatus;
	}
	public void move(Direction direction) {
		MotorStatus motorStatus = getMotorStatus() ;
		if (  motorStatus == MotorStatus.MOVING ) return ;
		
		DoorStatus doorStatus = door.getDoorStatus() ;
		if ( doorStatus == DoorStatus.OPENED )
			door.close() ;
		
		moveOtisMotor(direction) ;
		
		setMotorStatus(MotorStatus.MOVING) ;
	}
}

public class Door {
	private DoorStatus doorStatus ;
	public Door() {
		doorStatus = DoorStatus.CLOSED ;
	}
	public DoorStatus getDoorStatus() {
		return doorStatus ;
	}
	public void close() {
		doorStatus = DoorStatus.CLOSED ;
	}
	public void open() {
		doorStatus = DoorStatus.OPENED ;
	}
}

public enum DoorStatus { CLOSED, OPENED }
public enum Direction { UP, DOWN }
public enum MotorStatus { MOVING, STOPPED}

public class Client {
	public static void main(String[] args) {
		Door door = new Door() ;
		OtisMotor otisMotor = new OtisMotor(door) ;
		otisMotor.move(Direction.UP) ;
	}
}

 

만약 요기서 삼성 모터가 추가가 된다면 하단과 같이 삼성모터 클래스를 만든다.

 

 

public class SamsungMotor {
	private Door door ;
	private MotorStatus motorStatus ;
	
	public SamsungMotor(Door door) {
		this.door = door ;
		motorStatus = MotorStatus.STOPPED ;
	}	
	private void moveSamsungMotor(Direction direction) {
	
	}
	public MotorStatus getMotorStatus() {
		return motorStatus;
	}
	private void setMotorStatus(MotorStatus motorStatus) {
		this.motorStatus = motorStatus;
	}
	public void move(Direction direction) {
		MotorStatus motorStatus = getMotorStatus() ;
		if (  motorStatus == MotorStatus.MOVING ) return ;
		
		DoorStatus doorStatus = door.getDoorStatus() ;
		if ( doorStatus == DoorStatus.OPENED )
			door.close() ;
		
		moveSamsungMotor(direction) ;
		
		setMotorStatus(MotorStatus.MOVING) ;
	}
}


public class Client {
	public static void main(String[] args) {	
		Door door = new Door() ;
		SamsungMotor samsungMotor = new SamsungMotor(door) ;
		samsungMotor.move(Direction.UP) ;
	}
}

 

그런데  오티스 모터와 삼성모터의 코드 중복이 심해진다

 

그래서 모터 추상클래스를 만들고 공통된 부분을 넣는다 

 

public abstract class Motor {
	protected Door door ;
	private MotorStatus motorStatus ;
	
	public Motor(Door door) {
		this.door = door ;
		motorStatus = MotorStatus.STOPPED ;
	}	
	public MotorStatus getMotorStatus() {
		return motorStatus;
	}
	protected void setMotorStatus(MotorStatus motorStatus) {
		this.motorStatus = motorStatus;
	}
}


public class OtisMotor extends Motor {
	public OtisMotor(Door door) {
		super(door) ;
	}	
	private void moveOtisMotor(Direction direction) {
		
	}
	public void move(Direction direction) {
		MotorStatus motorStatus = getMotorStatus() ;
		if (  motorStatus == MotorStatus.MOVING ) return ;
		
		DoorStatus doorStatus = door.getDoorStatus() ;
		if ( doorStatus == DoorStatus.OPENED )
			door.close() ;
		
		moveOtisMotor(direction) ;
		
		setMotorStatus(MotorStatus.MOVING) ;
	}
}



public class SamsungMotor extends Motor {
	public SamsungMotor(Door door) {
		super(door) ;
	}	
	private void moveSamsungMotor(Direction direction) {
		
	}
	public void move(Direction direction) {
		MotorStatus motorStatus = getMotorStatus() ;
		if (  motorStatus == MotorStatus.MOVING ) return ;
		
		DoorStatus doorStatus = door.getDoorStatus() ;
		if ( doorStatus == DoorStatus.OPENED )
			door.close() ;
		
		moveSamsungMotor(direction) ;
		
		setMotorStatus(MotorStatus.MOVING) ;
	}
}

 

 

그럼에도 불구하고 move 메소드 내부는 여전히 겹치는 부분이 많다.

 

이럴때 필요한 것이 템플릿 메소드다.

 

move 메소드 속에 추상메소드인 hook 메소드를 삽입한다.

 

public abstract class Motor {
	private Door door ;
	private MotorStatus motorStatus ;
	
	public Motor(Door door) {
		this.door = door ;
		motorStatus = MotorStatus.STOPPED ;
	}	
	public MotorStatus getMotorStatus() {
		return motorStatus;
	}
	private void setMotorStatus(MotorStatus motorStatus) {
		this.motorStatus = motorStatus;
	}
	public void move(Direction direction) {
		MotorStatus motorStatus = getMotorStatus() ;
		if (  motorStatus == MotorStatus.MOVING ) return ;
		
		DoorStatus doorStatus = door.getDoorStatus() ;
		if ( doorStatus == DoorStatus.OPENED )
			door.close() ;
		
		moveMotor(direction) ; //hook, primitive 메소드라한다
		
		setMotorStatus(MotorStatus.MOVING) ;
	}
	protected abstract void moveMotor(Direction direction) ;
}




public class OtisMotor extends Motor {
	public OtisMotor(Door door) {
		super(door) ;
	}	
	protected void moveMotor(Direction direction) {
		// OtisMotor Motor내부 구현
	}
}


public class SamsungMotor extends Motor {
	public SamsungMotor(Door door) {
		super(door) ;
	}	
	protected void moveMotor(Direction direction) {
		// LG Motor내부 구현
	}
}

 

 

 

실무에서 사용하는 예시...

@Service
public class AaaServiceImpl extends GenericServiceImpl<A, Long> implements AaaService {

	@Resource
	private AaaRepository aaaRepository;
	
	@Override
	public GenericRepository<A, Long> initializingRepository() {
		return aaaRepository;
	}
    .....

 

public abstract class GenericServiceImpl<T, PK extends Serializable> implements GenericService<T, PK> {
    private GenericRepository<T, PK> domainRepository;

    public GenericServiceImpl() {
    }

    public GenericRepository<T, PK> getDomainRepository() {
        if (this.domainRepository == null) {
            this.domainRepository = this.initializingRepository();
        }

        return this.domainRepository;
    }

    public abstract GenericRepository<T, PK> initializingRepository();
    
    
    @Transactional
    public T add(T entity) {
        return this.getDomainRepository().insert(entity);
    }

    @Transactional
    public T edit(T entity) {
        return this.getDomainRepository().update(entity);
    }

    @Transactional
    public void remove(PK id) {
        this.getDomainRepository().delete(id);
    }

    @Transactional(readOnly = true)
    public T findById(PK id) {
        return this.getDomainRepository().selectById(id);
    }

 

 

2. 팩토리 메소드 패턴

 

객체를 생성하는 인터페이스는 미리 정의하고 서브클래스에 인스턴스 결정 및 책임을 위임

인스턴스를 생성하는 공장을 템플릿 메서드 패턴으로 만든것이 팩토리 메서드 패턴임

 

 

https://en.wikipedia.org/wiki/Factory_method_pattern