Pascal (Lazarus/Delphi)

Manually Follow HTTP Redirects

See more HTTP Examples

Demonstrates how to manually follow redirects for an HTTP GET. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.HttpResponse,
  Chilkat.Http;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  resp: THttpResponse;
  status: Integer;
  loopCount: Integer;
  nextUrl: string;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  http := THttp.Create;

  //  The FollowRedirects property controls whether redirects
  //  are automatically followed.  The default behavior is to
  //  automatically follow redirects.

  //  Explicitly set FollowRedirects so that redirects are NOT automatically taken:
  http.FollowRedirects := False;

  resp := THttpResponse.Create;
  success := http.HttpNoBody('GET','http://yandex.ru/',resp);
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  status := resp.StatusCode;
  WriteLn('HTTP Response Status: ' + status);

  //  The FinalRedirectUrl property will contain the redirect URL
  //  If FollowRedirects was equal to True, then all of the 
  //  intermediate redirects (if any) would be followed until
  //  there were no more redirects.  However, because 
  //  FollowRedirects is not True, FinalRedirectUrl contains
  //  the next redirect URL.

  loopCount := 0;

  while (status = 302) do
    begin

      WriteLn('Redirect URL: ' + http.FinalRedirectUrl);

      nextUrl := http.FinalRedirectUrl;
      success := http.HttpNoBody('GET',nextUrl,resp);
      if (success = False) then
        begin
          WriteLn(http.LastErrorText);
          Exit;
        end;

      status := resp.StatusCode;
      WriteLn('HTTP Response Status: ' + status);

      //  For safety, prevent infinite loops by
      //  keeping a loopCount and only allows following a max 
      //  of 10 redirects:
      loopCount := loopCount + 1;
      if (loopCount > 10) then
        begin
          WriteLn('Too many redirects.');
          Exit;
        end;

    end;



  http.Free;
  resp.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.