delphi json（CDS包含了Delta数据包）

在delphi中，数据集是最常用数据存取方式。因此，必须建立JSON与TDataSet之间的互转关系，实现数据之间通讯与转换。值得注意的是，这只是普通的TDataset与JSON之间转换，由于CDS包含了Delta数据包，其数据格式远比普通的TDataset更复杂。

数据集字段信息，是一个完整的字典信息。因此，我们在JSON必须也建立字典信息，才能创建数据集的字段信息。我们设置其JSON信息如下：

COLS:[字段列表信息]，如：

"Cols":[{"JsonType":"integer","FieldIndex":0,"FieldType":"Integer","FieldSize":0,"FieldName":"ID","Required":false},{"JsonType":"string","FieldIndex":1,"FieldType":"String","FieldSize":100,"FieldName":"Title","Required":false},{"JsonType":"variant","FieldIndex":2,"FieldType":"Blob","FieldSize":0,"FieldName":"Picture","Required":false}]

数据信息以Data做节点，也是一个数组嵌套记录信息：

"Data":[记录集信息]

废话少说，直接上代码：

1. unit uDBJson;
2. interface
3. uses
4. SysUtils,Classes,Variants,DB,DBClient,SuperObject;
5. type
6. TTableJSon = class
7. private
8. const cstFieldType = 'FieldType';
9. const cstFieldName = 'FieldName';
10. const cstFieldSize = 'FieldSize';
11. const cstJsonType = 'JsonType';
12. const cstRequired = 'Required';
13. const cstFieldIndex = 'FieldIndex';
14. const cstCols= 'Cols';
15. const cstData= 'Data';
16. public
17. class function JSonFromDataSet(DataSet:TDataSet):string;
18. class function CreateFieldByJson(Fields:TFieldDefs;ColsJson:ISuperObject):Boolean;
19. class function ImportDataFromJSon(DataSet:TDataSet;DataJson:ISuperObject):Integer;
20. class function CDSFromJSon(CDS:TClientDataSet;Json:ISuperObject):Boolean;
21. class function GetValue(Json:ISuperObject;const Name:string):Variant;
22. class function CreateJsonValue(Json:ISuperObject;const Name:string;const Value:Variant):Boolean;
23. class function CreateJsonValueByField(Json:ISuperObject;Field:TField):Boolean;
24. class function GetValue2Field(Field:TField;JsonValue:ISuperObject):Variant;
25. end;
26. implementation
27. uses TypInfo,encddecd;
28. { TTableJSon }
29. class function TTableJSon.CDSFromJSon(CDS: TClientDataSet;
30. Json: ISuperObject): Boolean;
31. var
32. ColsJson:ISuperObject;
33. begin
34. Result := False;
35. if Json = nil then
36. Exit;
37. CDS.Close;
38. CDS.Data := Null;
39. //创建字段
40. ColsJson := Json.O[cstCols];
41. CreateFieldByJson(CDS.FieldDefs,ColsJson);
42. if CDS.FieldDefs.Count >0 then
43. CDS.CreateDataSet;
44. ImportDataFromJSon(CDS,Json.O[cstData]);
45. Result := True;
46. end;
47. class function TTableJSon.CreateFieldByJson(Fields: TFieldDefs;
48. ColsJson: ISuperObject): Boolean;
49. var
50. SubJson:ISuperObject;
51. ft:TFieldType;
52. begin
53. Result := False;
54. Fields.DataSet.Close;
55. Fields.Clear;
56. for SubJson in ColsJson do
57. begin
58. ft := TFieldType(GetEnumValue(TypeInfo(TFieldType),'ft'+SubJson.S[cstFieldType]));
59. if ft= ftAutoInc then //自增字段不能录入，必须更改
60. ft := ftInteger;
61. Fields.Add(SubJson.S[cstFieldName],ft,SubJson.I[cstFieldSize],SubJson.B[cstRequired]);
62. end;
63. Result := True;
64. end;
65. class function TTableJSon.CreateJsonValue(Json: ISuperObject;
66. const Name: string; const Value: Variant): Boolean;
67. begin
68. Result := False;
69. Json.O[Name] := SO(Value);
70. Result := True;
71. end;
72. class function TTableJSon.CreateJsonValueByField(Json: ISuperObject;
73. Field: TField): Boolean;
74. begin
75. Result := False;
76. if Field Is TDateTimeField then
77. Json.O[Field.FieldName] := SO(Field.AsDateTime)
78. else if Field is TBlobField then
79. Json.S[Field.FieldName] := EncodeString(Field.AsString)
80. else
81. Json.O[Field.FieldName] := SO(Field.Value);
82. Result := True;
83. end;
84. class function TTableJSon.GetValue(
85. Json: ISuperObject;const Name: string): Variant;
86. begin
87. case Json.DataType of
88. stNull: Result := Null;
89. stBoolean: Result := Json.B[Name];
90. stDouble: Result := Json.D[Name];
91. stCurrency: Result := Json.C[Name];
92. stInt: Result := Json.I[Name];
93. stString: Result := Json.S[Name];
94. end;
95. end;
96. class function TTableJSon.GetValue2Field(Field: TField; JsonValue:ISuperObject): Variant;
97. begin
98. if JsonValue.DataType = stNull then
99. Result := Null
100. else if Field is TDateTimeField then
101. Result := JavaToDelphiDateTime(JsonValue.AsInteger)
102. else if (Field is TIntegerField) or (Field is TLargeintField) then
103. Result := JsonValue.AsInteger
104. else if Field is TNumericField then
105. Result := JsonValue.AsDouble
106. else if Field is TBooleanField then
107. Result := JsonValue.AsBoolean
108. else if Field is TStringField then
109. Result := JsonValue.AsString
110. else if Field is TBlobField then
111. Result := DecodeString(JsonValue.AsString)
112. end;
113. class function TTableJSon.ImportDataFromJSon(DataSet: TDataSet;
114. DataJson: ISuperObject): Integer;
115. var
116. SubJson:ISuperObject;
117. i:Integer;
118. iter: TSuperObjectIter;
119. begin
120. if not DataSet.Active then
121. DataSet.Open;
122. DataSet.DisableControls;
123. try
124. for SubJson in DataJson do
125. begin
126. DataSet.Append;
127. if ObjectFindFirst(SubJson,iter) then
128. begin
129. repeat
130. if DataSet.FindField(iter.Ite.Current.Name)<>nil then
131. DataSet.FindField(iter.Ite.Current.Name).Value :=
132. GetValue2Field(
133. DataSet.FindField(iter.Ite.Current.Name),
134. iter.Ite.Current.Value);
135. until not ObjectFindNext(iter) ;
136. end;
137. DataSet.Post;
138. end;
139. finally
140. DataSet.EnableControls;
141. end;
142. end;
143. class function TTableJSon.JSonFromDataSet(DataSet:TDataSet):string;
144. procedure GetFieldTypeInfo(Field:TField;var Fieldtyp,JsonTyp:string);
145. begin
146. Fieldtyp := GetEnumName(TypeInfo(tfieldtype),ord(Field.DataType));
147. Delete(Fieldtyp,1,2);
148. if Field is TStringField then
149. JsonTyp := 'string'
150. else if Field is TDateTimeField then
151. JsonTyp := 'integer'
152. else if (Field is TIntegerField) or (Field is TLargeintField) then
153. JsonTyp := 'integer'
154. else if Field is TCurrencyField then
155. JsonTyp := 'currency'
156. else if Field is TNumericField then
157. JsonTyp := 'double'
158. else if Field is TBooleanField then
159. JsonTyp := 'boolean'
160. else
161. JsonTyp := 'variant';
162. end;
163. var
164. sj,aj,sj2:ISuperObject;
165. i:Integer;
166. Fieldtyp,JsonTyp:string;
167. List:TStringList;
168. begin
169. sj := SO();
170. //创建列
171. aj := SA([]);
172. List := TStringList.Create;
173. try
174. List.Sorted := True;
175. for i := 0 to DataSet.FieldCount - 1 do
176. begin
177. sj2 := SO();
178. GetFieldTypeInfo(DataSet.Fields[i],Fieldtyp,JsonTyp);
179. sj2.S[cstFieldName] := DataSet.Fields[i].FieldName;
180. sj2.S[cstFieldType] := Fieldtyp;
181. sj2.S[cstJsonType] := JsonTyp;
182. sj2.I[cstFieldSize] := DataSet.Fields[i].Size;
183. sj2.B[cstRequired] := DataSet.Fields[i].Required;
184. sj2.I[cstFieldIndex] := DataSet.Fields[i].Index;
185. aj.AsArray.Add(sj2);
186. List.Add(DataSet.Fields[i].FieldName+'='+JsonTyp);
187. end;
188. sj.O['Cols'] := aj;
189. //创建数据集的数据
190. DataSet.DisableControls;
191. DataSet.First;
192. aj := SA([]);
193. while not DataSet.Eof do
194. begin
195. sj2 := SO();
196. for i := 0 to DataSet.FieldCount - 1 do
197. begin
198. //sj2.S[IntToStr(DataSet.Fields[i].Index)] := VarToStrDef(DataSet.Fields[i].Value,'');
199. if VarIsNull(DataSet.Fields[i].Value) then
200. sj2.O[DataSet.Fields[i].FieldName] := SO(Null)
201. else
202. begin
203. CreateJsonValueByField(sj2,DataSet.Fields[i]);
204. end;
205. end;
206. aj.AsArray.Add(sj2);
207. DataSet.Next;
208. end;
209. sj.O['Data'] := aj;
210. Result := sj.AsString;
211. finally
212. List.Free;
213. DataSet.EnableControls;
214. end;
215. end;
216. end.
217. 调用示例：
218. //数据集转JSON对象或JSON文本
219. var
220. json:TTableJSon;
221. s:string;
222. begin
223. S := json.JSonFromDataSet(ADODataSet1);
224. //在用TStringStream读入字符串S，存成文本，看看其格式.
225. end;
226. //JSON对象或文本，装载到数据集
227. var
228. json:ISuperObject;
229. begin
230. json := TSuperObject.ParseFile('json.txt',False);
231. TTableJSon.CDSFromJSon(cdsJSON,json);
232. end;

http://blog.csdn.net/diligentcatrich/article/details/6913512