(Delphi ActiveX) Manually Follow HTTP Redirects

Demonstrates how to manually follow redirects for an HTTP GET.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
http: TChilkatHttp;
resp: IChilkatHttpResponse;
status: Integer;
loopCount: Integer;
nextUrl: WideString;

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

http := TChilkatHttp.Create(Self);

// 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 := 0;

resp := http.QuickGetObj('http://yandex.ru/');
if (http.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

status := resp.StatusCode;
Memo1.Lines.Add('HTTP Response Status: ' + IntToStr(status));

// The FinalRedirectUrl property will contain the redirect URL
// If FollowRedirects was equal to 1, then all of the 
// intermediate redirects (if any) would be followed until
// there were no more redirects.  However, because 
// FollowRedirects is not 1, FinalRedirectUrl contains
// the next redirect URL.

loopCount := 0;

while (status = 302) do
  begin

    // IMPORTANT: This example requires Chilkat v9.5.0.49 or greater because
    // the FinalRedirectUrl in prior versions is only set when redirects
    // are automatically followed.   Starting in v9.5.0.49, the FinalRedirectUrl is
    // set to the next redirect URL when a 301/302 response is received, regardless
    // of the value of the FollowRedirects property.
    Memo1.Lines.Add('Redirect URL: ' + http.FinalRedirectUrl);

    nextUrl := http.FinalRedirectUrl;
    resp := http.QuickGetObj(nextUrl);
    if (http.LastMethodSuccess = 0) then
      begin
        Memo1.Lines.Add(http.LastErrorText);
        Exit;
      end;

    status := resp.StatusCode;
    Memo1.Lines.Add('HTTP Response Status: ' + IntToStr(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

        Memo1.Lines.Add('Too many redirects.');
        Exit;
      end;

  end;
end;