Design Patterns in Java (Creational) - Memento Pattern

Memento Pattern

• Used to provide undo actions
• Externalize internal state

Main

public static void main(String[] args) {





  

  Caretaker c = new Caretaker();

  

  Employee e = new Employee();

  e.setName("Chalan");

  e.setNumber("11111111");

  e.setAddress("NA");

  

  c.save(e);

  

  System.out.println(e);

  

  e.setNumber("2w222222");

  

  c.save(e);

  

  e.setNumber("33333");

  

  System.out.println(e);

  

  c.revert(e);

  

  System.out.println(e);

  

  c.revert(e);

  

  System.out.println(e);

 }

Caretaker

public class Caretaker {






 private Stack<EmployeeMemento> history = new Stack<EmployeeMemento>();

 

 public void save(Employee e){

  history.push(e.save());

 }

 

 public void revert(Employee e){

  e.revert(history.pop());

 }

}

Employee

public class Employee {





 

 private String name;

 private String number;

 private transient String address;

 //getters & setters
}

EmployeeMemento

public class EmployeeMemento {







 private String name;

 private String number;

 

 public EmployeeMemento( String name, String number){

  this.name = name;

  this.number = number;

 }

 

 public String getName() {

  return name;

 }

 public String getNumber() {

  return number;

 }

 

}