Delphi DLL

Get the Last-Modified Date Before HTTP Download

See more HTTP Examples

Demonstrates how to send a HEAD request to get the last-modified date of a file on a web server (without downloading the file). Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
http: HCkHttp;
resp: HCkHttpResponse;
lastModStr: PWideChar;
ckdt: HCkDateTime;
dt: HCkDtObj;

begin
success := False;

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

http := CkHttp_Create();

resp := CkHttpResponse_Create();
success := CkHttp_HttpNoBody(http,'HEAD','https://www.chilkatsoft.com/hamlet.xml',resp);
if (success = False) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

// Examine the response header.
Memo1.Lines.Add(CkHttpResponse__header(resp));

// Here is a sample response header:

// 	Content-Length: 279658
// 	Content-Type: text/xml
// 	Last-Modified: Thu, 12 May 2016 15:14:08 GMT
// 	Accept-Ranges: bytes
// 	ETag: "c1cd8bee60acd11:0"
// 	Server: Microsoft-IIS/8.5
// 	X-Powered-By: ASP.NET
// 	X-Powered-By-Plesk: PleskWin
// 	Date: Thu, 25 Jul 2019 16:40:54 GMT

// Get the Last-Modified header.
lastModStr := CkHttpResponse__getHeaderField(resp,'Last-Modified');
// If the header exists...
if (CkHttpResponse_getLastMethodSuccess(resp) = True) then
  begin
    // Parse the RFC822 format date/time string
    ckdt := CkDateTime_Create();
    CkDateTime_SetFromRfc822(ckdt,lastModStr);

    // If we want to access individual date/time parts (in the local timezone)
    dt := CkDtObj_Create();
    CkDateTime_ToDtObj(ckdt,True,dt);

    Memo1.Lines.Add('day/month/year = ' + IntToStr(CkDtObj_getDay(dt)) + '/' + IntToStr(CkDtObj_getMonth(dt)) + '/' + IntToStr(CkDtObj_getYear(dt)));
  end;

CkHttp_Dispose(http);
CkHttpResponse_Dispose(resp);
    CkDateTime_Dispose(ckdt);
    CkDtObj_Dispose(dt);

end;