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BIN\XML\JSON，三种格式。

firedac数据集数据序列为JSON字符串：

1 procedure TForm1.Button1Click(Sender: TObject);
2 begin
3   var ss: TStringStream := TStringStream.Create('', TEncoding.UTF8);
4   FDQuery1.SaveToStream(ss, sfJSON);
5   Memo1.Text := ss.DataString;
6   ss.Free;
7 end;
8

 1 procedure TForm1.Button3Click(Sender: TObject);
 2 var
 3   memtable: TFDMemTable;
 4   ms: TStringStream;
 5 begin
 6   memtable := FDMemTable2;
 7   memtable.CachedUpdates := True;
 8   if memtable.State in dsEditModes then
 9     memtable.Post;
10   if memtable.ChangeCount = 0 then
11     Exit;
12   memtable.ResourceOptions.StoreItems := [siDelta, siMeta];
13   ms := TStringStream.Create('', TEncoding.UTF8);
14   try
15     memtable.SaveToStream(ms, sfJSON);
16     Memo1.Text := ms.DataString;
17   finally
18     ms.Free;
19     memtable.ResourceOptions.StoreItems := [siDelta, siMeta, siData];
20   end;
21 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;