delphi json（CDS包含了Delta数据包）

Posted 2020-06-16

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

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