在delphi中，數據集是最常用數據存取方式。因此，必須建立JSON與TDataSet之間的互轉關系，實現數據之間通訊與轉換。值得注意的是，這只是普通的TDataset與JSON之間轉換，由于CDS包含了Delta數據包，其數據格式遠比普通的TDataset更復雜。

數據集字段信息，是一個完整的字典信息。因此，我們在JSON必須也建立字典信息，才能創建數據集的字段信息。我們設置其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}]

數據信息以Data做節點，也是一個數組嵌套記錄信息：

"Data":[記錄集信息]

廢話少說，直接上代碼：unit uDBJson;

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interface

uses

SysUtils,Classes,Variants,DB,DBClient,SuperObject;

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type

TTableJSon = class

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private

??? const cstFieldType = 'FieldType';

??? const cstFieldName = 'FieldName';

??? const cstFieldSize = 'FieldSize';

??? const cstJsonType = 'JsonType';

??? const cstRequired = 'Required';

??? const cstFieldIndex = 'FieldIndex';

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??? const cstCols= 'Cols';

??? const cstData= 'Data';

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public

??? class function JSonFromDataSet(DataSet:TDataSet):string;

??? class function CreateFieldByJson(Fields:TFieldDefs;ColsJson:ISuperObject):Boolean;

??? class function ImportDataFromJSon(DataSet:TDataSet;DataJson:ISuperObject):Integer;

??? class function CDSFromJSon(CDS:TClientDataSet;Json:ISuperObject):Boolean;

??? class function GetValue(Json:ISuperObject;const Name:string):Variant;

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??? class function CreateJsonValue(Json:ISuperObject;const Name:string;const Value:Variant):Boolean;

??? class function CreateJsonValueByField(Json:ISuperObject;Field:TField):Boolean;

??? class function GetValue2Field(Field:TField;JsonValue:ISuperObject):Variant;

end;

implementation

uses TypInfo,encddecd;

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{ TTableJSon }

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class function TTableJSon.CDSFromJSon(CDS: TClientDataSet;

Json: ISuperObject): Boolean;

var

ColsJson:ISuperObject;

begin

Result := False;

if Json = nil then

??? Exit;

CDS.Close;

CDS.Data := Null;

//創建字段

ColsJson := Json.O[cstCols];

CreateFieldByJson(CDS.FieldDefs,ColsJson);

if CDS.FieldDefs.Count >0 then

??? CDS.CreateDataSet;

ImportDataFromJSon(CDS,Json.O[cstData]);

Result := True;

end;

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class function TTableJSon.CreateFieldByJson(Fields: TFieldDefs;

ColsJson: ISuperObject): Boolean;

var

SubJson:ISuperObject;

ft:TFieldType;

begin

Result := False;

Fields.DataSet.Close;

Fields.Clear;

for SubJson in ColsJson do

begin

??? ft := TFieldType(GetEnumValue(TypeInfo(TFieldType),'ft'+SubJson.S[cstFieldType]));

??? if ft= ftAutoInc then //自增字段不能錄入，必須更改

????? ft := ftInteger;

??? Fields.Add(SubJson.S[cstFieldName],ft,SubJson.I[cstFieldSize],SubJson.B[cstRequired]);

end;

Result := True;

end;

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class function TTableJSon.CreateJsonValue(Json: ISuperObject;

const Name: string; const Value: Variant): Boolean;

begin

Result := False;

Json.O[Name] := SO(Value);

Result := True;

end;

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class function TTableJSon.CreateJsonValueByField(Json: ISuperObject;

Field: TField): Boolean;

begin

Result := False;

if Field Is TDateTimeField then

??? Json.O[Field.FieldName] := SO(Field.AsDateTime)

else if Field is TBlobField then

??? Json.S[Field.FieldName] := EncodeString(Field.AsString)

else

??? Json.O[Field.FieldName] := SO(Field.Value);

Result := True;

end;

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class function TTableJSon.GetValue(

Json: ISuperObject;const Name: string): Variant;

begin

case Json.DataType of

??? stNull: Result := Null;

??? stBoolean: Result := Json.B[Name];

??? stDouble: Result := Json.D[Name];

??? stCurrency: Result := Json.C[Name];

??? stInt: Result := Json.I[Name];

??? stString: Result := Json.S[Name];

end;

end;

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class function TTableJSon.GetValue2Field(Field: TField; JsonValue:ISuperObject): Variant;

begin

if JsonValue.DataType = stNull then

??? Result := Null

else if Field is TDateTimeField then

??? Result := JavaToDelphiDateTime(JsonValue.AsInteger)

else if (Field is TIntegerField) or (Field is TLargeintField) then

??? Result := JsonValue.AsInteger

else if Field is TNumericField then

??? Result := JsonValue.AsDouble

else if Field is TBooleanField then

??? Result := JsonValue.AsBoolean

else if Field is TStringField then

??? Result := JsonValue.AsString

else if Field is TBlobField then

??? Result := DecodeString(JsonValue.AsString)???

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end;

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class function TTableJSon.ImportDataFromJSon(DataSet: TDataSet;

DataJson: ISuperObject): Integer;

var

SubJson:ISuperObject;

i:Integer;

iter: TSuperObjectIter;

begin

if not DataSet.Active then

??? DataSet.Open;

DataSet.DisableControls;

try

??? for SubJson in DataJson do

??? begin

????? DataSet.Append;

????? if ObjectFindFirst(SubJson,iter) then

????? begin

???????? repeat

?????????? if DataSet.FindField(iter.Ite.Current.Name)<>nil then

???????????? DataSet.FindField(iter.Ite.Current.Name).Value :=

??????????????? GetValue2Field(

??????????????? DataSet.FindField(iter.Ite.Current.Name),

??????????????? iter.Ite.Current.Value);

???????? until not ObjectFindNext(iter) ;

????? end;

????? DataSet.Post;

??? end;

finally

??? DataSet.EnableControls;

end;

end;

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class function TTableJSon.JSonFromDataSet(DataSet:TDataSet):string;

procedure GetFieldTypeInfo(Field:TField;var Fieldtyp,JsonTyp:string);

begin

??? Fieldtyp := GetEnumName(TypeInfo(tfieldtype),ord(Field.DataType));

??? Delete(Fieldtyp,1,2);

??? if Field is TStringField then

????? JsonTyp := 'string'

??? else if Field is TDateTimeField then

????? JsonTyp := 'integer'

??? else if (Field is TIntegerField) or (Field is TLargeintField) then

????? JsonTyp := 'integer'

??? else if Field is TCurrencyField then

????? JsonTyp := 'currency'

??? else if Field is TNumericField then

????? JsonTyp := 'double'

??? else if Field is TBooleanField then

????? JsonTyp := 'boolean'

??? else

????? JsonTyp := 'variant';

end;

var

sj,aj,sj2:ISuperObject;

i:Integer;

Fieldtyp,JsonTyp:string;

List:TStringList;

begin

sj := SO();

//創建列

aj := SA([]);

List := TStringList.Create;

try

??? List.Sorted := True;

??

??? for i := 0 to DataSet.FieldCount - 1 do

??? begin

????? sj2 := SO();

????? GetFieldTypeInfo(DataSet.Fields[i],Fieldtyp,JsonTyp);

???

????? sj2.S[cstFieldName] := DataSet.Fields[i].FieldName;

????? sj2.S[cstFieldType] := Fieldtyp;

????? sj2.S[cstJsonType] := JsonTyp;

????? sj2.I[cstFieldSize] := DataSet.Fields[i].Size;

????? sj2.B[cstRequired] := DataSet.Fields[i].Required;

????? sj2.I[cstFieldIndex] := DataSet.Fields[i].Index;

????? aj.AsArray.Add(sj2);

????? List.Add(DataSet.Fields[i].FieldName+'='+JsonTyp);

??? end;

??? sj.O['Cols'] := aj;

??? //創建數據集的數據

??? DataSet.DisableControls;

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??? DataSet.First;

??? aj := SA([]);

??? while not DataSet.Eof do

??? begin

????? sj2 := SO();

????? for i := 0 to DataSet.FieldCount - 1 do

????? begin

??????? //sj2.S[IntToStr(DataSet.Fields[i].Index)] := VarToStrDef(DataSet.Fields[i].Value,'');

??????? if VarIsNull(DataSet.Fields[i].Value) then

????????? sj2.O[DataSet.Fields[i].FieldName] := SO(Null)

??????? else

??????? begin

????????? CreateJsonValueByField(sj2,DataSet.Fields[i]);

??????? end;

????? end;

????? aj.AsArray.Add(sj2);

????? DataSet.Next;

??? end;

??? sj.O['Data'] := aj;

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??? Result := sj.AsString;

finally

??? List.Free;

??? DataSet.EnableControls;

end;

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end;

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end.

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調用示例：

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//數據集轉JSON對象或JSON文本

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var

json:TTableJSon;

s:string;

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begin

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S := json.JSonFromDataSet(ADODataSet1);

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//在用TStringStream讀入字符串S，存成文本，看看其格式.

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end;

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//JSON對象或文本，裝載到數據集

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var

json:ISuperObject;

begin

json := TSuperObject.ParseFile('json.txt',False);

TTableJSon.CDSFromJSon(cdsJSON,json);

end;
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