Delphi XE6 FireDAC - Export TFDQuery recordset to JSON - json

Question

I'm using FireDAC in Delphi XE6 to query a database (Pervasive) through ODBC. I have a TFDQuery component which runs my SELECT query and returns the records. Once the query is complete I want to export the data in the recordset as JSON. I've tried using the following code :
fdacQuery.SaveToStream(myStream, sfJSON);
This creates JSON, but only for the table definition i.e. field names, data types, constraints etc. - there is no representation of the data. Is there another method I should be using to export just the recordset data as JSON? Is there another solution?

Answer 1

Try this on for size then. I did it for a utility I needed yesterday. It uses SuperObject. I left all field types in the code in case you want to add other special treatments or tweak any of those I put in. It's working for me on many random datasets right now.
class procedure TTool.ExportDataSetToJson(DataSet: TDataSet; FileName: string; Append: boolean = false);
const
SData = 'data';
var
json : ISuperObject;
item : ISuperObject;
wasActive: boolean;
fld : TField;
begin
json := SO;
json.O[SData] := SA([]);
wasActive := DataSet.Active;
try
DataSet.Active := true;
DataSet.First;
while not DataSet.Eof do
begin
item := SO;
for fld in DataSet.Fields do
begin
case fld.DataType of
// ftUnknown: ;
ftString,
ftBlob,
ftMemo,
ftFmtMemo,
ftBytes,
ftVarBytes,
ftFixedChar,
ftFixedWideChar,
ftWideMemo,
ftByte,
ftWideString: item.S[fld.FieldName] := fld.AsString;
ftBoolean: item.B[fld.FieldName] := fld.AsBoolean;
ftFloat,
ftSingle,
ftExtended,
ftCurrency,
ftFMTBcd,
ftBCD: item.D[fld.FieldName] := fld.AsFloat;
ftTime : item.S[fld.FieldName] := TimeToJson(fld.AsDateTime);
ftDate,
ftTimeStamp,
ftOraTimeStamp,
ftDateTime: item.S[fld.FieldName] := DateTimeToJson(fld.AsDateTime);
ftSmallint,
ftInteger,
ftWord,
ftAutoInc,
ftLongWord,
ftShortint,
ftLargeInt: item.I[fld.FieldName] := fld.AsLargeInt;
// ftGraphic: ;
// ftParadoxOle: ;
// ftDBaseOle: ;
// ftTypedBinary: ;
// ftCursor: ;
// ftADT: ;
// ftArray: ;
// ftReference: ;
// ftDataSet: ;
// ftOraBlob: ;
// ftOraClob: ;
// ftVariant: ;
// ftInterface: ;
// ftIDispatch: ;
ftGuid: item.S[fld.FieldName] := fld.AsString;
// ftOraInterval: ;
// ftConnection: ;
// ftParams: ;
// ftStream: ;
// ftTimeStampOffset: ;
// ftObject: ;
else
item.S[fld.FieldName] := fld.AsString;
end;
end;
DataSet.Next;
json.A[SData].Add(item);
end;
if Append then
TFile.AppendAllText(FileName, json.AsJSon(true, true))
else
json.SaveTo(FileName, true, true);
finally
DataSet.Active := wasActive;
end;
end;

Answer 2

Have you looked at the code in the tutorial at http://docwiki.embarcadero.com/RADStudio/XE8/en/Tutorial:_Using_a_REST_DataSnap_Server_with_an_Application_and_FireDAC yet?
// Create dataset list
Result := TFDJSONDataSets.Create;
// Add departments dataset
TFDJSONDataSetsWriter.ListAdd(Result, sDepartment, FDQueryDepartment);
// Add employees dataset
TFDJSONDataSetsWriter.ListAdd(Result, sEmployees, FDQueryDepartmentEmployees);