FDQuery，FDMemTable将修改后的数据序列为JSON

firedac数据集数据序列为JSON

FIREDAC数据库引擎充分地考虑了跨平台和跨语言的支持。

因此，FIREDAC数据集可以序列为BINXMLJSON，三种格式。

firedac数据集数据序列为JSON字符串：

procedure TForm1.Button1Click(Sender: TObject);
begin
  var ss: TStringStream := TStringStream.Create('', TEncoding.UTF8);
  FDQuery1.SaveToStream(ss, sfJSON);
  Memo1.Text := ss.DataString;
  ss.Free;
end;
　　

procedure TForm1.Button3Click(Sender: TObject);
var
  memtable: TFDMemTable;
  ms: TStringStream;
begin
  memtable := FDMemTable2;
  memtable.CachedUpdates := True;
  if memtable.State in dsEditModes then
    memtable.Post;
  if memtable.ChangeCount = 0 then
    Exit;
  memtable.ResourceOptions.StoreItems := [siDelta, siMeta];
  ms := TStringStream.Create('', TEncoding.UTF8);
  try
    memtable.SaveToStream(ms, sfJSON);
    Memo1.Text := ms.DataString;
  finally
    ms.Free;
    memtable.ResourceOptions.StoreItems := [siDelta, siMeta, siData];
  end;
end;

流导入到FDMEMTable时  必须把流指向起始的位置 

procedure TForm_JSON.B_1Click(Sender: TObject);
var
Astream, Astream2: TStringStream;
aa, aa1: string;
Js: TJsonSerializer;
begin
Astream := TStringStream.Create;
FDQuery1.Open;


FDQuery1.SaveToStream(Astream,sfjson);
Astream.position := 0;//  这一句十分重要   在这里十分感谢咏南兄
// FDQuery1.SaveToStream(Astream, sfjson);
FDMemTable1.Close;
// FDMemTable1.LoadFromStream(Astream,sfXML);
FDMemTable1.LoadFromStream(Astream,sfJSON);

end;