第十六篇:备忘录模式

说在开头:其实我个人并不认为这是什么设计模式...因为完全没有什么价值嘛，不过既然多本书上对其有介绍，那我还是写一下吧！

备忘录模式是用来实现 备份，还原 的一种代码组织结构；  什么时候需要备份还原呢？非常常见的是游戏中的保存进度， 打BOSS前需要先将当前进度保存一下，等到一不小心挂了，还可以马上恢复到打BOSS前...不然得江湖再见一切重头开始，那该多蛋疼？？？

那好，我们就以游戏为例写一段代码吧！

//游戏角色
class Role{
	//攻击点数
	private int attackCount;
	//防御点数
	private int defenceForcesCount;
	//经验数
	private int experieceCount;
	//精力//该数是不需要存档的...
	private int vigorCount;
	public int getAttackCount() {
		return attackCount;
	}
	public void setAttackCount(int attackCount) {this.attackCount = attackCount;}
	public int getDefenceForcesCount() {return defenceForcesCount;}
	public void setDefenceForcesCount(int defenceForcesCount) {this.defenceForcesCount = defenceForcesCount;}
	public int getExperieceCount() {return experieceCount;}
	public void setExperieceCount(int experieceCount) {this.experieceCount = experieceCount;}
	public int getVigorCount() {return vigorCount;}
	public void setVigorCount(int vigorCount) {this.vigorCount = vigorCount;}
	
	@Override
	public String toString() {
		return "Role [attackCount=" + attackCount + ", defenceForcesCount="
				+ defenceForcesCount + ", experieceCount=" + experieceCount
				+ ", vigorCount=" + vigorCount + "]";
	}
	
}

//备份数据管理者接口，也就是存档位置，
//我们在单机游戏中不是可以看到多个存档点么,我们可以自由选择存档点嘛！
interface Director{
	//备份
	void preserve(Role role );
	//读取存档点还原
	Role rollBack();
}
//存档位置1
class DirectorOne implements Director{
	
	private Role role;
	@Override
	public void preserve(Role role) {
		this.role = role;
	}
	@Override
	public Role rollBack() {
		return this.role;
	}
}

//备份帮助者对象，这里注意一下，其实我们可以直接对Role对象进行克隆，完全复制一份进行保存而不要这个对象，
//之所以一个个属性去get and set，是因为可能有某些值是不需要备份的，比如精力
class BackHelper{
	/***
	 * 进行备份的地方
	 * @param role 要备份的角色
	 * @param director 要备份到那个存档点
	 */
	public void preserve( Role role,Director director){
		Role newRole = new Role();
		newRole.setAttackCount(role.getAttackCount());
		newRole.setDefenceForcesCount(role.getDefenceForcesCount());
		newRole.setExperieceCount(role.getExperieceCount());
		director.preserve(newRole);
	}
}

最后来测试一下：

public class Test {
	public static void main(String[] args) {
		Role role = new Role();
		role.setAttackCount(10);
		role.setDefenceForcesCount(88);
		role.setExperieceCount(100);
		role.setVigorCount(72);
		System.out.println(role);
		//备份一下，保存到存档点
		Director director = new DirectorOne();
		BackHelper backHelper = new BackHelper();
		backHelper.preserve(role, director);
		
		//戴上了某件超强装备，改变攻击力
		role.setAttackCount(10000);
		System.out.println(role);
		
		//打BOSS死了，重新读档
		role = director.rollBack();
		System.out.println(role);
	}
}

输出******************************************************************

Role [attackCount=10, defenceForcesCount=88, experieceCount=100, vigorCount=72]
Role [attackCount=10000, defenceForcesCount=88, experieceCount=100, vigorCount=72]
Role [attackCount=10, defenceForcesCount=88, experieceCount=100, vigorCount=0]

***********************************************************************

Ok，就写这么多吧，实在没什么好些的...