数据集和JSON相互转换

使用DELPHI原生类实现数据集和JSON相互转换

 JSON二要素：数组和对象。对象可以包含数组，数组可以包含对象。无层数限制。OLEVARIANT也类似，OLEVARIANT的一个元素又可以是OLEVARIANT，且无层数限制。XML亦类似。这也是它们能序列一切对象的奥秒所在。
JSON就是字符串，定义好序列后的字符串格式，甚至都不需要啥JSON类库，就可以自行组装JSON字符串和解析JSON字串获取数据。

USES System.JSON

1）数据集转换为JSON字符串：

function TForm1.DataSetToJson(ADataset: TDataSet): string;
// [{"CityId":"18","CityName":"西安"},{"CityId":"53","CityName":"广州"}]
var
LRecord: string;
LField: TField;
i: integer;
begin
Result := '';
if (not ADataset.Active) or (ADataset.IsEmpty) then
Exit;
Result := '[';
ADataset.DisableControls;
ADataset.First;
while not ADataset.Eof do
begin
for i := 0 to ADataset.FieldCount - 1 do
begin
LField := ADataset.Fields[i];
if LRecord = '' then
LRecord := '{"' + LField.FieldName + '":"' + LField.Text + '"'
else
LRecord := LRecord + ',"' + LField.FieldName + '":"' + LField.Text + '"';
if i = ADataset.FieldCount - 1 then
begin
LRecord := LRecord + '}';
if Result = '[' then
Result := Result + LRecord
else
Result := Result + ',' + LRecord;
LRecord := '';
end;
end;
ADataset.Next;
end;
ADataset.EnableControls;
Result := Result + ']';
end;

2）JSON字符串转换为数据集：

procedure TForm1.JsonToDataSet(AJson: string; ADataset: TDataSet);
var
jDataSet: TJSONArray;
jRecord: TJSONObject;
i, j: Integer;
begin
if (AJson = '') or (ADataset = nil) or (not ADataset.Active) then
Exit;
jDataSet := TJSONObject.Create.ParseJSONValue(AJson, True) as TJSONArray;
while not ADataset.Eof do
ADataset.Delete;
for i := 0 to jDataSet.Size - 1 do
begin
ADataset.Append;
jRecord := jDataSet.Get(i) as TJSONObject;
for j := 0 to ADataset.FieldCount - 1 do
ADataset.Fields[j].Text := jRecord.GetValue(ADataset.Fields[j].FieldName).ToString;
ADataset.Post;
end;
end;