使用Delphi从Amazon下载文件

Question

I am working with an API that provides me with the URL of a file and I wish to download the file to file or stream using Delphi XE.

The URL is in this form:-

https://xxxxxxx.s3-us-west-2.amazonaws.com/xxx/Reports/414_20160114021919.pdf?AWSAccessKeyId=xxxxxxxxxxxxxx&Expires=1478915858&response-content-disposition=attachment%3Bfilename%3D%22123%20Test%20St%20Dallas__2016_01_14_03_16_00.pdf%22&Signature=xxxxxxxxxxx%3D

where I have xxxxxxxxx'ed out the sensitive security stuff.

If I paste the URL into Chrome, it finds the file and brings up the save dialog.

In my Delphi Program I'm using URLMon with the following code (happily burgled and adapted from answers to similar questions here on SO) :-

function TdmXXXXXXXXX.DownloadFile(AURL, AExtWithDot: string): string;
// returns temp file name or empty string if failed;
var
  sTempFileName: string;
  iError: integer;
begin
  sTempFileName := apmDM.GetTempFileName(AExtWithDot, True);
  iError := UrlDownloadToFile(nil, PChar(AURL), PChar(sTempFileName), 0, nil);
  if iError = S_OK then
    Result := sTempFileName
  else
    Result := '';
  showmessage(SysUtils.IntToHex(iError,8));
end;

The showmessage returns "800C000D"

In URLMon:-

$EXTERNALSYM INET_E_UNKNOWN_PROTOCOL}
INET_E_UNKNOWN_PROTOCOL            = HResult($800C000D);

So I'm assuming that the problem relates to stuff after the "?" in the URL, "AWSAccessKeyId=" etc.

Not sure where to go from here - searched here and with Mr Google ...

Cheers Jeff

Answer 1

Though you'll typically find pointers to the Indy TIdHTTP component, my personal favorite is including the Microsoft XML library (MSXML2_TLB), and using the XmlHTTPRequest component. If you use a TStreamAdapter on it's responseStream property, you'll have a stream to a resource over an URL.

Answer 2

I scratched all that I had done and restarted from scratch.

It all worked using URLMon and URLDownloadToFile(nil, PChar(sReportURL), PChar(sTempFileName), 0, nil);

I have pored over the code and can't see any difference between reported problem code and my final code.