服务端对WCF数据实例分析

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publicclassMySyncProvider:KnowledgeSyncProvider,IChangeDataRetriever,INotifyingChangeApplierTarget  

1. {  

2. //Thenameofthemetadatastorecustomcolumnthatisusedtosaveatimestampoflastchangeonan  

3. //iteminthemetadatastoresowecandochangedetection.  

4. conststringTIMESTAMP_COLUMNNAME="timestamp";  

5. //Thisisoursampleinmemorydatastorewhichforsimplicty,storessetsofstringname-ProcessChangeBatchpairs  

6. //referencedbyidentifiersofthetype'Guid'  

7. MySimpleDataStore_store;  

8. //UsetheSyncFramework'soptionalmetadatastoretotrackversioninformation  

9. SqlMetadataStore_metadataStore=null;//表示通过使用轻型数据库存储元数据来实现的元数据存储区。  

10. ReplicaMetadata_metadata=null;//提供对元数据存储区中的副本元数据和项元数据的访问。ReplicaMetadata还对删除检测和用于实现同步提供程序方法的帮助器提供服务  

11. privatestring_name=null;  

12. privatestring_folderPath=null;  

13. privatestring_replicaMetadataFile=null;  

14. privatestring_replicaIdFile=null;  

15. //Theprovider'suniqueidentifier  

16. SyncId_replicaId=null;  

17. SyncIdFormatGroup_idFormats=null;  

18. SyncSessionContext_currentSessionContext=null;  

19. //Constructadatastorebyprovidinganamefortheendpoint(replica)and  

20. //afiletowhichwe'llpersistthesyncmetadata(file)  

21. publicMySyncProvider(stringfolderPath,stringname)  

22. {  

23. namename=name;  

24. folderPathfolderPath=folderPath;  

25. replicaMetadataFile=_folderPath.ToString()+""+_name.ToString()+".Metadata";  

26. replicaIdFile=_folderPath.ToString()+""+_name.ToString()+".Replicaid";  

27. SetItemIdFormatandReplicaIdFormatforusingGuidids.  

28. idFormats=newSyncIdFormatGroup();  

29. idFormats.ItemIdFormat.IsVariableLength=false;  

30. idFormats.ItemIdFormat.Length=16;  

31. idFormats.ReplicaIdFormat.IsVariableLength=false;  

32. idFormats.ReplicaIdFormat.Length=16;  

33. }  

34. publicSyncIdReplicaId  

35. {  

36. get  

37. {  

38. if(_replicaId==null)  

39. {  

40. replicaId=GetReplicaIdFromFile(_replicaIdFile);  

41. }  

42. return_replicaId;  

43. }  

44. }  

45. #regionMetadataStoreRelatedMethods  

46. privatevoidInitializeMetadataStore()  

47. {  

48. Valuesforaddingacustomfieldtothemetadatastore  

49. List<FieldSchema>fields=newList<FieldSchema>();  

50. SyncIdid=ReplicaId;  

51. Createoropenthemetadatastore,initializingitwiththeidformatswe'llusetoreferenceouritemsandendpoints  

52. if(!File.Exists(_replicaMetadataFile))  

53. {  

54. fields.Add(newFieldSchema(TIMESTAMP_COLUMNNAME,typeof(System.UInt64)));  

55. //创建一个具有指定名称和位置的元数据存储区文件，然后返回表示该文件的元数据存储区对象。  

56. _metadataStore=SqlMetadataStore.CreateStore(_replicaMetadataFile);  

57. //在元数据存储区创建和初始化副本的元数据，并返回一个用于访问该副本元数据的副本元数据对象。  

58. _metadata=_metadataStore.InitializeReplicaMetadata(_idFormats,//提供程序的ID格式架构  

59. replicaId,//与此元数据相关联的副本ID  

60. fields,//每个元数据项的自定义元数据字段的架构信息集合。如果不存在自定义元数据字段，则可为null引用  

61. null);//可用于更有效地查找元数据存储区中的项的索引架构列表。如果不存在自定义索引，则可以是null引用  

62. }  

63. else  

64. {  

65. _metadataStore=SqlMetadataStore.OpenStore(_replicaMetadataFile);//打开现有的元数据存储区文件，并返回表示该文件的元数据存储区对象  

66. _metadata=_metadataStore.GetReplicaMetadata(_idFormats,_replicaId);//获取用于访问元数据存储区中的副本元数据的副本元数据对象。  

67. }  

68. }  

69. privatevoidCloseMetadataStore()  

70. {  

71. metadataStore.Dispose();  

72. metadataStore=null;  

73. }  

74. //Updatethemetadatastorewithchangesthathaveoccuredonthedatastoresincethelasttimeitwasupdated.  

75. publicvoidUpdateMetadataStoreWithLocalChanges()  

76. {  

77. SyncVersionnewVersion=newSyncVersion(0,_metadata.GetNextTickCount());  

78. metadata.DeleteDetector.MarkAllItemsUnreported();  

79. foreach(Guididin_store.Ids)  

80. {  

81. ItemDatadata=_store.Get(id);  

82. ItemMetadataitem=null;  

83. //Lookupanitem'smetadatabyitsID  

84. item=_metadata.FindItemMetadataById(newSyncId(id));  

85. if(null==item)  

86. {  

87. Newitem,musthavebeencreatedsincethatlasttimethemetadatawasupdated.  

88. Createtheitemmetadatarequiredforsync(givingitaSyncIDandaversion,definedtobeaDWORDandaULONGLONG  

89. Forcreates,simplyprovidetherelativereplicaID(0)andthetickcountfortheprovider(everincreasing)  

90. item=_metadata.CreateItemMetadata(newSyncId(id),newVersion);  

91. item.ChangeVersion=newVersion;  

92. SaveItemMetadata(item,data.TimeStamp);  

93. }  

94. else  

95. {  

96. if(data.TimeStamp>item.GetUInt64Field(TIMESTAMP_COLUMNNAME))//theitemhaschangedsincethelastsyncoperation.  

97. {  

98. //ChangedItem,thisitemhaschangedsincethelasttimethemetadatawasupdated.  

99. //Assignanewversionbysimplystating"who"modifiedthisitem(0=local/me)and"when"(tickcountforthestore)  

100. item.ChangeVersion=newVersion;  

101. SaveItemMetadata(item,data.TimeStamp);  

102. }  

103. else  

104. {  

105. //Unchangeditem,nothinghaschangessojustmarkitaslivesothatthemetadataknowsithasnotbeendeleted.  

106. _metadata.DeleteDetector.ReportLiveItemById(newSyncId(id));  

107. }  

108. }  

109. }  

110. Nowgobackthroughtheitemsthatarenolongerinthestoreandmarkthemasdeletedinthemetadata.　  

111. Thissetstheitemasatombstone.  

112. foreach(ItemMetadataitemin_metadata.DeleteDetector.FindUnreportedItems())  

113. {  

114. item.MarkAsDeleted(newVersion);  

115. SaveItemMetadata(item,0);//settimestampto0fortombstones  

116. }  

117. }  

118. privatevoidSaveItemMetadata(ItemMetadataitem,ulongtimeStamp)  

119. {  

120. item.SetCustomField(TIMESTAMP_COLUMNNAME,timeStamp);  

121. SaveItemMetadata(item);  

122. }  

123. privatevoidSaveItemMetadata(ItemMetadataitem)  

124. {  

125. metadata.SaveItemMetadata(item);  

126. }  

127. //MethodforcleaninguptombstonesolderthanacertainTimeSpan  

128. publicvoidCleanupTombstones(TimeSpantimespan)  

129. {  

130. InitializeMetadataStore();  

131. metadataStore.BeginTransaction();//对元数据存储区启动显式事务  

132. metadata.CleanupDeletedItems(timespan);  

133. metadataStore.CommitTransaction();//提交已对元数据存储区启动的显式事务  

134. CloseMetadataStore();  

135. }  

136. #endregionMetadataStoreRelatedMethods  

137. #regionKnowledgeSyncProviderOverrides  

138. //BeginSessioniscalledatthebeginningofeachsyncoperation.　Doinitializationhere.　Forexampleupdate  

139. //metadataifitwasnotupdatedastheactualdatawaschanged.  

140. publicoverridevoidBeginSession(SyncProviderPositionposition,SyncSessionContextsyncSessionContext)  

141. {  

142. BeginSession();  

143. currentSessionContext=syncSessionContext;  

144. }  

145. //EndSessioniscalledafterthesyncoperationiscompleted.　Cleanuphappenshere.  

146. publicoverridevoidEndSession(SyncSessionContextsyncSessionContext)  

147. {  

148. EndSession();  

149. }  

150. //Simplyaskthemetadatastoretocomputemychangebatchforme,providingthebatchsizeandtheknowledgeoftheotherendpoint!  

151. //Theengineisaskingforthelistofchangesthatthedestinationproviderdoesnotknowabout.  

152. //SyncKnowledge:表示副本所具有的有关自己项存储区的知识。  

153. //此类型的所有公共静态（在VisualBasic中共享）成员都是线程安全的。不保证任何实例成员的线程安全。  

154. publicoverrideChangeBatchGetChangeBatch(uintbatchSize,SyncKnowledgedestinationKnowledge,outobjectchangeDataRetriever)  

155. {  

156. ChangeBatchbatch=_metadata.GetChangeBatch(batchSize,destinationKnowledge);  

157. changeDataRetriever=this;//thisiswherethetransfermechanism/protocolwouldgo.Foraninmemoryprovider,thisissufficient  

158. returnbatch;  

159. }  

160. //ThisisonlycalledwhentheenginehasdetectedthatthedestinationisoutofdateduetoTombstonecleanup.  

161. publicoverrideFullEnumerationChangeBatchGetFullEnumerationChangeBatch(uintbatchSize,SyncIdlowerEnumerationBound,SyncKnowledgeknowledgeForDataRetrieval,outobjectchangeDataRetriever)  

162. {  

163. FullEnumerationChangeBatchbatch=_metadata.GetFullEnumerationChangeBatch(batchSize,lowerEnumerationBound,knowledgeForDataRetrieval);  

164. changeDataRetriever=this;//thisiswherethetransfermechanism/protocolwouldgo.Foraninmemoryprovider,thisissufficient  

165. returnbatch;  

166. }  

167. //指定batchSize为10，以及相应的知识  

168. publicoverridevoidGetSyncBatchParameters(outuintbatchSize,outSyncKnowledgeknowledge)  

169. {  

170. batchSize=10;  

171. knowledge=_metadata.GetKnowledge();  

172. }  

173. //应用修改  

174. publicoverridevoidProcessChangeBatch(ConflictResolutionPolicyresolutionPolicy,ChangeBatchsourceChanges,  

175. objectchangeDataRetriever,SyncCallbackssyncCallback,SyncSessionStatisticssessionStatistics)  

176. {  

177. metadataStore.BeginTransaction();  

178. 从原数据存储中获得取得本地所有修改  

179. IEnumerable<ItemChange>localChanges=_metadata.GetLocalVersions(sourceChanges);  

180. Createachangeapplierobjecttomakechangeapplicationeasier(maketheenginecallme  

181. whenitneedsdataandwhenIshouldsavedata)  

182. NotifyingChangeApplierchangeApplier=newNotifyingChangeApplier(_idFormats);  

183. changeApplier.ApplyChanges(resolutionPolicy,sourceChanges,changeDataRetrieverasIChangeDataRetriever,localChanges,_metadata.GetKnowledge(),  

184. _metadata.GetForgottenKnowledge(),this,_currentSessionContext,syncCallback);  

185. metadataStore.CommitTransaction();  

186. }  

187. //Iffullenumerationisneededbecause　thisproviderisoutofdateduetotombstonecleanup,thenthismethodwillbecalledbytheengine.  

188. publicoverridevoidProcessFullEnumerationChangeBatch(ConflictResolutionPolicyresolutionPolicy,FullEnumerationChangeBatchsourceChanges,objectchangeDataRetriever,SyncCallbackssyncCallback,SyncSessionStatisticssessionStatistics)  

189. {  

190. metadataStore.BeginTransaction();  

191. Getallmylocalchangeversionsfromthemetadatastore  

192. IEnumerable<ItemChange>localChanges=_metadata.GetFullEnumerationLocalVersions(sourceChanges);  

193. Createachangeapplierobjecttomakechangeapplicationeasier(maketheenginecallme  

194. whenitneedsdataandwhenIshouldsavedata)  

195. NotifyingChangeApplierchangeApplier=newNotifyingChangeApplier(_idFormats);  

196. changeApplier.ApplyFullEnumerationChanges(resolutionPolicy,sourceChanges,changeDataRetrieverasIChangeDataRetriever,localChanges,_metadata.GetKnowledge(),  

197. _metadata.GetForgottenKnowledge(),this,_currentSessionContext,syncCallback);  

198. metadataStore.CommitTransaction();  

199. } 

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