jSon_encode like function for Delphi which accepts TDataSet - delphi

Question

I have been tasked with creating a Indy server in Delphi 2007 which communicates with clients and returns json formatted data from Sql based databases. Someone from our office created a prototype using php. And in the prototype they use the jSon_encode function extensively to return the data from tables. I was wondering if there was a similar Delphi function which could accept a TDataSet parameter and return properly formatted json data.
Anyone know of such function?
Update 12/10/2013 - my modification to #user2748835 answer:
function jsonencode(mString: String): String;
begin
result := StringReplace(mString,'''','\''',[rfReplaceAll,rfIgnoreCase]);
result := StringReplace(mString,'\','\\',[rfReplaceAll,rfIgnoreCase]);
result := StringReplace(result,crlf,'\n',[rfReplaceAll,rfIgnoreCase]);
result := StringReplace(result,'"','\"',[rfReplaceAll,rfIgnoreCase]);
result := StringReplace(result,'/','\/',[rfReplaceAll,rfIgnoreCase]);
result := StringReplace(result,'#9','\t',[rfReplaceAll,rfIgnoreCase]);
end;
function jSon_encode(aDataset:TDataset):string;
function fieldToJSON(thisField:TField):string;
begin
try
result := '"'+thisField.fieldName+'":';
case thisField.DataType of
ftInteger,ftSmallint,ftLargeint:
result := result+inttostr(thisField.AsInteger);
ftDateTime:
result := result+'"'+formatdatetime('YYYY-MM-DD HH:NN:SS',thisField.AsDateTime)+'"';
ftCurrency,
ftFloat:
result := result + floattostr(thisField.AsFloat);
ftString :
result := result + '"'+jsonencode(thisField.AsString)+'"';
else
end; // case
result := result + ',';
except
on e: Exception do begin
appendtolog('problem escaping field '+thisfield.fieldname);
end;
end;
end; // of fieldToJSON
function rowToJSON(ds:TDataset):string;
var
fieldIx : integer;
begin
result := '';
for fieldIx := 0 to ds.fieldcount-1 do
result := result + fieldToJSON(ds.Fields[fieldIx]);
// trim comma after last col
result := '{'+copy(result,1,length(result)-1)+'},';
end; // of rowToJSON
begin
result := '';
with aDataset do
begin
if not bof then first;
while not eof do
begin
result := result + rowToJSON(aDataset);
next;
end;
end;
//strip last comma and add
if length(result)>0 then
result := copy(result,1,length(result)-1);
result := '['+result+']';
end; // of DSToJSON

Answer 1

In a TDataset, you can loop through the Fields collection and construct the json output and then in the loop, check the fieldtype and encode the value accordingly.
Something like:
uses db;
function DSToJSON(aDataset:TDataset):string;
function fieldToJSON(thisField:TField):string;
begin
result := '"'+thisField.fieldName+'":';
case thisField.DataType of
ftInteger,
ftSmallint,
ftCurrency,
ftFloat,
ftLargeInt:
result := result+thisField.value+^n^j;
ftString :
result := noSingleQuotes(thisField.value)+^n^j;
else
end; // case
end; // of fieldToJSON
function rowToJSON(ds:TDataset):string;
var
fieldIx : integer;
begin
for fieldIx := 0 to ds.fieldcount-1 do
result := result + fieldToJSON(ds.Fields[fieldIx]);
// trim comma after last col
result := '{'+copy(result,1,length(result)-1)+'},';
end; // of rowToJSON
begin
result := '';
with aDataset do
begin
if not bof then first;
while not eof do
begin
result := result + rowToJSON(aDataset);
next;
end;
end;
//strip last comma and add
if length(result)>0 then
result := copy(result,1,length(result)-1);
result := '['+result+']';
end; // of DSToJSON

Answer 2

We just added a more complete and faster function, in our Open Source repository.
It is part of our mORMot framework, but can be used as a stand-alone unit, not tied to other features.
See in SynVirtualDataSet.pas:
function DataSetToJSON(Data: TDataSet): RawUTF8
See this commit and the associated forum thread.

Answer 3

You can change every row into object and use serializing http://docwiki.embarcadero.com/RADStudio/XE5/en/Serializing_User_Objects