(Delphi DLL) Manually Follow HTTP Redirects

Demonstrates how to manually follow redirects for an HTTP GET.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
http: HCkHttp;
resp: HCkHttpResponse;
status: Integer;
loopCount: Integer;
nextUrl: PWideChar;

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

http := CkHttp_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:
CkHttp_putFollowRedirects(http,False);

resp := CkHttp_QuickGetObj(http,'http://yandex.ru/');
if (CkHttp_getLastMethodSuccess(http) = False) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

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

    // 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: ' + CkHttp__finalRedirectUrl(http));

    CkHttpResponse_Dispose(resp);

    nextUrl := CkHttp__finalRedirectUrl(http);
    resp := CkHttp_QuickGetObj(http,nextUrl);
    if (CkHttp_getLastMethodSuccess(http) = False) then
      begin
        Memo1.Lines.Add(CkHttp__lastErrorText(http));
        Exit;
      end;

    status := CkHttpResponse_getStatusCode(resp);
    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
        CkHttpResponse_Dispose(resp);
        Memo1.Lines.Add('Too many redirects.');
        Exit;
      end;

    CkHttpResponse_Dispose(resp);

  end;

CkHttp_Dispose(http);

end;