备忘录模式(Memento Pattern)

淡淡的烟草味﹌ 2022-03-31 03:28 245阅读 0赞

[设计模式 - 吕震宇][-]

[.NET设计模式系列文章][.NET]

[薛敬明的专栏][Link 1]

[乐在其中设计模式(C\#)][C]

# [设计模式23：Memento Pattern (备忘录模式)][23_Memento Pattern] #

英文原文：[http://www.dofactory.com/Patterns/PatternMemento.aspx][http_www.dofactory.com_Patterns_PatternMemento.aspx]

### 一、Memento Pattern (备忘录模式) ###

Define:Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later.

定义：在不违反封装性，捕获和使得一个对象的内状态具体化，以至于这个对象可以被存储于这个状态之后。

### 二、UML类图 ###

![memento][]

*  **Memento** **(Memento)**
    
     *  stores internal state of the Originator object. The memento may store as much or as little of the originator's internal state as necessary at its originator's discretion.
     *  protect against access by objects of other than the originator. Mementos have effectively two interfaces. Caretaker sees a narrow interface to the Memento -- it can only pass the memento to the other objects. Originator, in contrast, sees a wide interface, one that lets it access all the data necessary to restore itself to its previous state. Ideally, only the originator that produces the memento would be permitted to access the memento's internal state.
 *  **Originator** **(SalesProspect)**
    
     *  creates a memento containing a snapshot of its current internal state.
     *  uses the memento to restore its internal state
 *  **Caretaker** **(Caretaker)**
    
     *  is responsible for the memento's safekeeping
     *  never operates on or examines the contents of a memento.
    
    ### 三、Memento Pattern (备忘录模式)实例代码 ###
    
    **\[c-sharp\]** [ view plain][view plain] [copy][view plain]
    
    1.  using System;
    2.  using System.Collections.Generic;
    3.  using System.Linq;
    4.  using System.Text;
    5.  
    6.  namespace Memento\_Pattern
    7.  \{
    8.  /// <summary>
    9.  
    10. /// MainApp startup class for Structural 
    11. 
    12. /// Memento Design Pattern.
    13. 
    14. /// </summary>
    15. 
    16. class MainApp
    17. \{
    18. 
    19. /// <summary>
    20. 
    21. /// Entry point into console application.
    22. 
    23. /// </summary>
    24. 
    25. static void Main()
    26. \{
    27. 
    28. Originator o = new Originator();
    29. 
    30. o.State = "On";
    31. 
    32. 
    33. 
    34. // Store internal state
    35. 
    36. Caretaker c = new Caretaker();
    37. 
    38. c.Memento = o.CreateMemento();
    39. 
    40. 
    41. 
    42. // Continue changing originator
    43. 
    44. o.State = "Off";
    45. 
    46. 
    47. 
    48. // Restore saved state
    49. 
    50. o.SetMemento(c.Memento);
    51. 
    52. 
    53. 
    54. // Wait for user
    55. 
    56. Console.ReadKey();
    57. 
    58. \}
    59. 
    60. \}
    61. 
    62. 
    63. 
    64. /// <summary>
    65. 
    66. /// The 'Originator' class
    67. 
    68. /// </summary>
    69. 
    70. class Originator
    71. \{
    72. 
    73. private string \_state;
    74. 
    75. 
    76. 
    77. // Property
    78. 
    79. public string State
    80. \{
    81. 
    82. get \{ return \_state; \}
    83. 
    84. set
    85. \{
    86. 
    87. \_state = value;
    88. 
    89. Console.WriteLine("State = " \+ \_state);
    90. 
    91. \}
    92. 
    93. \}
    94. 
    95. 
    96. 
    97. // Creates memento 
    98. 
    99. public Memento CreateMemento()
    100. \{
    101. 
    102. return (new Memento(\_state));
    103. 
    104. \}
    105. 
    106. 
    107. 
    108. // Restores original state
    109. 
    110. public void SetMemento(Memento memento)
    111. \{
    112. 
    113. Console.WriteLine("Restoring state...");
    114. 
    115. State = memento.State;
    116. 
    117. \}
    118. 
    119. \}
    120. 
    121. 
    122. 
    123. /// <summary>
    124. 
    125. /// The 'Memento' class
    126. 
    127. /// </summary>
    128. 
    129. class Memento
    130. \{
    131. 
    132. private string \_state;
    133. 
    134. 
    135. 
    136. // Constructor
    137. 
    138. public Memento(string state)
    139. \{
    140. 
    141. this.\_state = state;
    142. 
    143. \}
    144. 
    145. 
    146. 
    147. // Gets or sets state
    148. 
    149. public string State
    150. \{
    151. 
    152. get \{ return \_state; \}
    153. 
    154. \}
    155. 
    156. \}
    157. 
    158. 
    159. 
    160. /// <summary>
    161. 
    162. /// The 'Caretaker' class
    163. 
    164. /// </summary>
    165. 
    166. class Caretaker
    167. \{
    168. 
    169. private Memento \_memento;
    170. 
    171. 
    172. 
    173. // Gets or sets memento
    174. 
    175. public Memento Memento
    176. \{
    177. 
    178. set \{ \_memento = value; \}
    179. 
    180. get \{ return \_memento; \}
    181. 
    182. \}
    183. 
    184. \}
    185. \}
    
    ### 四、使用备忘录模式的实例代码 ###
    
    This real-world code demonstrates the Memento pattern which temporarily saves and then restores the SalesProspect's internal state.
    
    临时保存和恢复SalesProspect的内部状态
    
    **\[c-sharp\]** [ view plain][view plain] [copy][view plain]
    
    1.  using System;
    2.  using System.Collections.Generic;
    3.  using System.Linq;
    4.  using System.Text;
    5.  
    6.  namespace Memento\_Pattern
    7.  \{
    8.  /// <summary>
    9.  
    10. /// MainApp startup class for Real-World 
    11. 
    12. /// Memento Design Pattern.
    13. 
    14. /// </summary>
    15. 
    16. class MainApp
    17. \{
    18. 
    19. /// <summary>
    20. 
    21. /// Entry point into console application.
    22. 
    23. /// </summary>
    24. 
    25. static void Main()
    26. \{
    27. 
    28. SalesProspect s = new SalesProspect();
    29. 
    30. s.Name = "Noel van Halen";
    31. 
    32. s.Phone = "(412) 256-0990";
    33. 
    34. s.Budget = 25000.0;
    35. 
    36. 
    37. 
    38. // Store internal state
    39. 
    40. ProspectMemory m = new ProspectMemory();
    41. 
    42. m.Memento = s.SaveMemento();
    43. 
    44. 
    45. 
    46. // Continue changing originator
    47. 
    48. s.Name = "Leo Welch";
    49. 
    50. s.Phone = "(310) 209-7111";
    51. 
    52. s.Budget = 1000000.0;
    53. 
    54. 
    55. 
    56. // Restore saved state
    57. 
    58. s.RestoreMemento(m.Memento);
    59. 
    60. 
    61. 
    62. // Wait for user
    63. 
    64. Console.ReadKey();
    65. 
    66. \}
    67. 
    68. \}
    69. 
    70. 
    71. 
    72. /// <summary>
    73. 
    74. /// The 'Originator' class
    75. 
    76. /// </summary>
    77. 
    78. class SalesProspect
    79. \{
    80. 
    81. private string \_name;
    82. 
    83. private string \_phone;
    84. 
    85. private double \_budget;
    86. 
    87. 
    88. 
    89. // Gets or sets name
    90. 
    91. public string Name
    92. \{
    93. 
    94. get \{ return \_name; \}
    95. 
    96. set
    97. \{
    98. 
    99. \_name = value;
    100. 
    101. Console.WriteLine("Name: " \+ \_name);
    102. 
    103. \}
    104. 
    105. \}
    106. 
    107. 
    108. 
    109. // Gets or sets phone
    110. 
    111. public string Phone
    112. \{
    113. 
    114. get \{ return \_phone; \}
    115. 
    116. set
    117. \{
    118. 
    119. \_phone = value;
    120. 
    121. Console.WriteLine("Phone: " \+ \_phone);
    122. 
    123. \}
    124. 
    125. \}
    126. 
    127. 
    128. 
    129. // Gets or sets budget
    130. 
    131. public double Budget
    132. \{
    133. 
    134. get \{ return \_budget; \}
    135. 
    136. set
    137. \{
    138. 
    139. \_budget = value;
    140. 
    141. Console.WriteLine("Budget: " \+ \_budget);
    142. 
    143. \}
    144. 
    145. \}
    146. 
    147. 
    148. 
    149. // Stores memento
    150. 
    151. public Memento SaveMemento()
    152. \{
    153. 
    154. Console.WriteLine("/nSaving state --/n");
    155. 
    156. return new Memento(\_name, \_phone, \_budget);
    157. 
    158. \}
    159. 
    160. 
    161. 
    162. // Restores memento
    163. 
    164. public void RestoreMemento(Memento memento)
    165. \{
    166. 
    167. Console.WriteLine("/nRestoring state --/n");
    168. 
    169. this.Name = memento.Name;
    170. 
    171. this.Phone = memento.Phone;
    172. 
    173. this.Budget = memento.Budget;
    174. 
    175. \}
    176. 
    177. \}
    178. 
    179. 
    180. 
    181. /// <summary>
    182. 
    183. /// The 'Memento' class
    184. 
    185. /// </summary>
    186. 
    187. class Memento
    188. \{
    189. 
    190. private string \_name;
    191. 
    192. private string \_phone;
    193. 
    194. private double \_budget;
    195. 
    196. 
    197. 
    198. // Constructor
    199. 
    200. public Memento(string name, string phone, double budget)
    201. \{
    202. 
    203. this.\_name = name;
    204. 
    205. this.\_phone = phone;
    206. 
    207. this.\_budget = budget;
    208. 
    209. \}
    210. 
    211. 
    212. 
    213. // Gets or sets name
    214. 
    215. public string Name
    216. \{
    217. 
    218. get \{ return \_name; \}
    219. 
    220. set \{ \_name = value; \}
    221. 
    222. \}
    223. 
    224. 
    225. 
    226. // Gets or set phone
    227. 
    228. public string Phone
    229. \{
    230. 
    231. get \{ return \_phone; \}
    232. 
    233. set \{ \_phone = value; \}
    234. 
    235. \}
    236. 
    237. 
    238. 
    239. // Gets or sets budget
    240. 
    241. public double Budget
    242. \{
    243. 
    244. get \{ return \_budget; \}
    245. 
    246. set \{ \_budget = value; \}
    247. 
    248. \}
    249. 
    250. \}
    251. 
    252. 
    253. 
    254. /// <summary>
    255. 
    256. /// The 'Caretaker' class
    257. 
    258. /// </summary>
    259. 
    260. class ProspectMemory
    261. \{
    262. 
    263. private Memento \_memento;
    264. 
    265. 
    266. 
    267. // Property
    268. 
    269. public Memento Memento
    270. \{
    271. 
    272. set \{ \_memento = value; \}
    273. 
    274. get \{ return \_memento; \}
    275. 
    276. \}
    277. 
    278. \}
    279. \}
    
    # [乐在其中设计模式(C\#) - 备忘录模式(Memento Pattern)][C_ - _Memento Pattern] #
    
    乐在其中设计模式(C\#) - 备忘录模式(Memento Pattern)
    
      
      
    作者：[webabcd][]  
      
      
    介绍  
    在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到保存的状态。  
      
      
    示例  
    有一个Message实体类，某个对象对它的操作有Insert()方法，只有在插入时间符合要求的情况下才能插入成功，因此要求可以保存和恢复Message对象的状态，插入失败后则恢复Message对象的状态，然后只更新时间，再次插入。  
    ![o_Memento.png][]  
      
      
    MessageModel  
    
    
    ![None.gif][] using  System;  
    ![None.gif][] using  System.Collections.Generic;  
    ![None.gif][] using  System.Text;  
    ![None.gif][]  
    ![None.gif][] namespace  Pattern.Memento  
    ![ExpandedBlockStart.gif][] \{  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message实体类（Memento）  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]publicclass MessageModel  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// 构造函数  
    ![InBlock.gif][]///</summary>  
    ![InBlock.gif][]///<param name="msg">Message内容</param>  
    ![ExpandedSubBlockEnd.gif][]///<param name="pt">Message发布时间</param>  
    ![InBlock.gif][]public MessageModel(string msg, DateTime pt)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]this.\_message = msg;  
    ![InBlock.gif][]this.\_publishTime = pt;  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![InBlock.gif][]privatestring \_message;  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message内容  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]publicstring Message  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]get\{ return \_message; \}  
    ![ExpandedSubBlockStart.gif][]set\{ \_message = value; \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![InBlock.gif][]private DateTime \_publishTime;  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message发布时间  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]public DateTime PublishTime  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]get\{ return \_publishTime; \}  
    ![ExpandedSubBlockStart.gif][]set\{ \_publishTime = value; \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedBlockEnd.gif][]\}   
    ![None.gif][]
    
      
    MessageModelCaretaker  
    
    
    ![None.gif][] using  System;  
    ![None.gif][] using  System.Collections.Generic;  
    ![None.gif][] using  System.Text;  
    ![None.gif][]  
    ![None.gif][] namespace  Pattern.Memento  
    ![ExpandedBlockStart.gif][] \{  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Memento管理者（Caretaker）  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]publicclass MessageModelCaretaker  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]private MessageModel \_messageModel;  
    ![InBlock.gif][]  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message实体对象（Memento）  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]public MessageModel MessageModel  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]get\{ return \_messageModel; \}  
    ![ExpandedSubBlockStart.gif][]set\{ \_messageModel = value; \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedBlockEnd.gif][]\}   
    ![None.gif][]
    
      
    SqlMessage  
    
    
    ![None.gif][] using  System;  
    ![None.gif][] using  System.Collections.Generic;  
    ![None.gif][] using  System.Text;  
    ![None.gif][]  
    ![None.gif][] namespace  Pattern.Memento  
    ![ExpandedBlockStart.gif][] \{  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Sql方式操作Message（Originator）  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]publicclass SqlMessage  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]privatestring \_message;  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message内容  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]publicstring Message  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]get\{ return \_message; \}  
    ![ExpandedSubBlockStart.gif][]set\{ \_message = value; \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![InBlock.gif][]private DateTime \_publishTime;  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// Message发布时间  
    ![ExpandedSubBlockEnd.gif][]///</summary>  
    ![InBlock.gif][]public DateTime PublishTime  
    ![ExpandedSubBlockStart.gif][]\{  
    ![ExpandedSubBlockStart.gif][]get\{ return \_publishTime; \}  
    ![ExpandedSubBlockStart.gif][]set\{ \_publishTime = value; \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// 插入Message  
    ![InBlock.gif][]///</summary>  
    ![InBlock.gif][]///<param name="mm">Message实体对象</param>  
    ![ExpandedSubBlockEnd.gif][]///<returns></returns>  
    ![InBlock.gif][]publicbool Insert(MessageModel mm)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]// 秒数可以被5整除时，则执行插入操作  
    ![InBlock.gif][]if (mm.PublishTime.Second %5==0)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]// 代码略  
    ![InBlock.gif][]returntrue;  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]else  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]returnfalse;  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// 保存Memento  
    ![InBlock.gif][]///</summary>  
    ![ExpandedSubBlockEnd.gif][]///<returns></returns>  
    ![InBlock.gif][]public MessageModel SaveMemento()  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]returnnew MessageModel(\_message, \_publishTime);  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![InBlock.gif][]  
    ![ExpandedSubBlockStart.gif][]///<summary>  
    ![InBlock.gif][]/// 恢复Memento  
    ![InBlock.gif][]///</summary>  
    ![ExpandedSubBlockEnd.gif][]///<param name="mm"></param>  
    ![InBlock.gif][]publicvoid RestoreMemento(MessageModel mm)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][]this.\_message = mm.Message;  
    ![InBlock.gif][]this.\_publishTime = mm.PublishTime;  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedBlockEnd.gif][]\}   
    ![None.gif][]
    
      
      
    Test  
    
    
    ![None.gif][] using  System;  
    ![None.gif][] using  System.Data;  
    ![None.gif][] using  System.Configuration;  
    ![None.gif][] using  System.Collections;  
    ![None.gif][] using  System.Web;  
    ![None.gif][] using  System.Web.Security;  
    ![None.gif][] using  System.Web.UI;  
    ![None.gif][] using  System.Web.UI.WebControls;  
    ![None.gif][] using  System.Web.UI.WebControls.WebParts;  
    ![None.gif][] using  System.Web.UI.HtmlControls;  
    ![None.gif][]  
    ![None.gif][] using  Pattern.Memento;  
    ![None.gif][]  
    ![None.gif][] public  partial  class  Memento : System.Web.UI.Page  
    ![ExpandedBlockStart.gif][] \{  
    ![InBlock.gif][]protectedvoid Page\_Load(object sender, EventArgs e)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][] SqlMessage m =new SqlMessage();  
    ![InBlock.gif][] m.Message ="Message内容";  
    ![InBlock.gif][] m.PublishTime = DateTime.Now;  
    ![InBlock.gif][]  
    ![InBlock.gif][] MessageModelCaretaker mmc =new MessageModelCaretaker();  
    ![InBlock.gif][] mmc.MessageModel = m.SaveMemento();  
    ![InBlock.gif][]  
    ![InBlock.gif][]bool bln =false;  
    ![InBlock.gif][]while (!bln)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][] bln = m.Insert(new MessageModel(m.Message, m.PublishTime));  
    ![InBlock.gif][]  
    ![InBlock.gif][] Response.Write(m.Message \+""\+ m.PublishTime.ToString() \+""\+ bln.ToString());  
    ![InBlock.gif][] Response.Write("<br />");  
    ![InBlock.gif][]  
    ![InBlock.gif][]if (!bln)  
    ![ExpandedSubBlockStart.gif][]\{  
    ![InBlock.gif][] System.Threading.Thread.Sleep(1000);  
    ![InBlock.gif][]  
    ![InBlock.gif][] m.RestoreMemento(mmc.MessageModel);  
    ![InBlock.gif][] m.PublishTime = DateTime.Now;  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedSubBlockEnd.gif][] \}  
    ![ExpandedBlockEnd.gif][]\}   
    ![None.gif][]
    
      
    运行结果  
    Message内容 2007-5-23 21:32:13 False  
    Message内容 2007-5-23 21:32:14 False  
    Message内容 2007-5-23 21:32:15 True  
      
      
    参考  
    [http://www.dofactory.com/Patterns/PatternMemento.aspx][http_www.dofactory.com_Patterns_PatternMemento.aspx]  
      
      
    OK  
    [\[源码下载\]][Link 2]

[-]: http://www.cnblogs.com/zhenyulu/category/6930.html
[.NET]: http://www.cnblogs.com/Terrylee/archive/2006/07/17/334911.html
[Link 1]: http://blog.csdn.net/rocket5725/article/category/559017
[C]: http://www.cnblogs.com/webabcd/category/82668.html
[23_Memento Pattern]: http://blog.csdn.net/rocket5725/article/details/4334224
[http_www.dofactory.com_Patterns_PatternMemento.aspx]: http://www.dofactory.com/Patterns/PatternMemento.aspx
[memento]: /images/20220331/3a13aae080c84ba894b2be1b2652fc9e.png
[view plain]: http://blog.csdn.net/rocket5725/article/details/4334224#
[C_ - _Memento Pattern]: http://www.cnblogs.com/webabcd/archive/2007/05/23/757675.html
[webabcd]: http://webabcd.cnblogs.com/
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[Link 2]: http://files.cnblogs.com/webabcd/Pattern.rar