Mega Code Archive
Accessing DataBase via 3th server
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Title: Accessing DataBase via 3th server
Question: Writing n-tier Application for accessing client's app to DataBase without installing Client of Database via 3th server using Indy
Answer:
This is simple sample how organize work client's app with DataBase without installing Database client or organize remote access to database.
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, IdTCPServer, IdBaseComponent, IdComponent,
IdTCPConnection, IdTCPClient, DBClient, Provider, Grids, DBGrids, DB,
OracleData, Oracle, IdAntiFreezeBase, IdAntiFreeze;
type
TForm1 = class(TForm)
OracleSession1: TOracleSession;
OracleDataSet1: TOracleDataSet;
DataSource1: TDataSource;
DBGrid1: TDBGrid;
DataSetProvider1: TDataSetProvider;
ClientDataSet1: TClientDataSet;
IdTCPClient1: TIdTCPClient;
IdTCPServer1: TIdTCPServer;
Button1: TButton;
Memo1: TMemo;
IdAntiFreeze1: TIdAntiFreeze;
procedure Button1Click(Sender: TObject);
procedure IdTCPServer1Connect(AThread: TIdPeerThread);
procedure IdTCPServer1Execute(AThread: TIdPeerThread);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure variantToStream(const v: oleVariant; stream: TStream);
var p: pointer;
begin
stream.position:= 0;
stream.size:= varArrayHighBound(v,1) - varArrayLowBound(v,1)+1;
p:= varARrayLock(v);
stream.write(p^, stream.size);
varARrayUnlock(v);
stream.position:= 0;
end;
procedure VarArrayToStream(const Data: OleVariant; Stream: TStream);
var
p: Pointer;
begin
p := VarArrayLock(Data);
try
Stream.Write(p^, VarArrayHighBound(Data,1) + 1); //assuming low bound = 0
finally
VarArrayUnlock(Data);
end;
end;
function StreamToVarArray(Stream: TStream): OleVariant;
var
p: Pointer;
begin
Result := VarArrayCreate([0, Stream.Size - 1], varByte);
p := VarArrayLock(Result);
try
Stream.Position := 0; //start from beginning of stream
Stream.Read(p^, Stream.Size);
finally
VarArrayUnlock(Result);
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
ms:TMemoryStream;
begin
ms:=TMemoryStream.Create;
if not IdTCPClient1.Connected then IdTCPClient1.Connect;
if IdTCPClient1.Connected then
Memo1.Lines.Add('connected')
else
Memo1.Lines.Add('Not Connected');
IdTCPClient1.Write('open');
IdTCPClient1.ReadStream(ms,STrToINt(IdTCPClient1.ReadString(10)));
ClientDataSet1.Data:=StreamToVarArray(ms);
// ClientDataSet1.LoadFromStream(ms);
ClientDataSet1.Active:=True;
end;
procedure TForm1.IdTCPServer1Connect(AThread: TIdPeerThread);
begin
//
end;
procedure TForm1.IdTCPServer1Execute(AThread: TIdPeerThread);
var
s:string;
ms:TMemoryStream;
begin
with AThread.Connection do begin
s:=ReadString(4);
if s='open' then begin
ms:=TMemoryStream.Create;
VarArrayToStream(DataSetProvider1.Data,ms);
s:=IntToSTr(ms.Size);
while length(s) s:='0'+s;
end;
Write(s);
ms.Seek(0,soFromBeginning);
WriteStream(ms);
end;
end;
end;
end.
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