메멘토 패턴

1 개요[ | ]

memento pattern
메멘토 패턴

상태를 저장하는 구조
객체를 이전 상태에 되돌리는 기능(rollback)을 제공하는 디자인 패턴
originator와 caretaker

originator: 내부 상태를 가지는 객체

caretaker: originator의 변경을 되돌리는 능력을 가지는 객체

2 예제[ | ]

import java.util.List;
import java.util.ArrayList;
class Originator {
    private String state;
    // The class could also contain additional data that is not part of the
    // state saved in the memento.
 
    public void set(String state) {
        System.out.println("Originator: Setting state to " + state);
        this.state = state;
    }
 
    public Memento saveToMemento() {
        System.out.println("Originator: Saving to Memento.");
        return new Memento(state);
    }
 
    public void restoreFromMemento(Memento memento) {
        state = memento.getSavedState();
        System.out.println("Originator: State after restoring from Memento: " + state);
    }
 
    public static class Memento {
        private final String state;
 
        public Memento(String stateToSave) {
            state = stateToSave;
        }
 
        public String getSavedState() {
            return state;
        }
    }
}
 
class Caretaker {
    public static void main(String[] args) {
        List<Originator.Memento> savedStates = new ArrayList<Originator.Memento>();
 
        Originator originator = new Originator();
        originator.set("State1");
        originator.set("State2");
        savedStates.add(originator.saveToMemento());
        originator.set("State3");
        // We can request multiple mementos, and choose which one to roll back to.
        savedStates.add(originator.saveToMemento());
        originator.set("State4");
 
        originator.restoreFromMemento(savedStates.get(1));   
    }
}

Originator: Setting state to State1
Originator: Setting state to State2
Originator: Saving to Memento.
Originator: Setting state to State3
Originator: Saving to Memento.
Originator: Setting state to State4
Originator: State after restoring from Memento: State3

private Memento(State state)
{
    //state has to be cloned before returning the 
    //memento, or successive calls to get Memento
    //return a reference to the same object
    this.mementoState = state.clone();
}

3 같이 보기[ | ]

4 참고[ | ]

http://en.wikipedia.org/wiki/Memento_pattern