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：
unit uDBJson;
interface
uses
SysUtils,Classes,Variants,DB,DBClient,SuperObject;
type
TTableJSon = class
private
const cstFieldType = 'FieldType';
const cstFieldName = 'FieldName';
const cstFieldSize = 'FieldSize';
const cstJsonType = 'JsonType';
const cstRequired = 'Required';
const cstFieldIndex = 'FieldIndex';
const cstCols= 'Cols';
const cstData= 'Data';
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;
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;
{ TTableJSon }
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;
//创建字段
ColsJson := Json.O[cstCols];
CreateFieldByJson(CDS.FieldDefs,ColsJson);
if CDS.FieldDefs.Count >0 then
CDS.CreateDataSet;
ImportDataFromJSon(CDS,Json.O[cstData]);
Result := True;
end;
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 //自增字段不能录入，必须更改
ft := ftInteger;
Fields.Add(SubJson.S[cstFieldName],ft,SubJson.I[cstFieldSize],SubJson.B[cstRequired]);
end;
Result := True;
end;
class function TTableJSon.CreateJsonValue(Json: ISuperObject;
const Name: string; const Value: Variant): Boolean;
begin
Result := False;
Json.O[Name] := SO(Value);
Result := True;
end;
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;
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;
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)
end;
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;
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();
//创建列
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;
//创建数据集的数据
DataSet.DisableControls;
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;
Result := sj.AsString;
finally
List.Free;
DataSet.EnableControls;
end;
end;
end.
调用示例：
//数据集转JSON对象或JSON文本
var
json:TTableJSon;
s:string;
begin
S := json.JSonFromDataSet(ADODataSet1);
//在用TStringStream读入字符串S，存成文本，看看其格式.
end;
//JSON对象或文本，装载到数据集
var
json:ISuperObject;
begin
json := TSuperObject.ParseFile('json.txt',False);
TTableJSon.CDSFromJSon(cdsJSON,json);
end;