Pascal (Lazarus/Delphi)

Generate an AWS (S3) Pre-Signed URL to Download File

See more Amazon S3 (new) Examples

Demonstrates how to generate a pre-signed URL to download a file from the Amazon S3 service. 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.Http;

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

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  bucketName: string;
  objectName: string;
  localFilePath: string;
  awsService: string;
  numSecondsValid: Integer;
  bUseHttps: Boolean;
  preSignedUrl: string;

begin
  success := False;

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

  http := THttp.Create;

  http.AwsAccessKey := 'AWS_ACCESS_KEY';
  http.AwsSecretKey := 'AWS_SECRET_KEY';

  //  Make sure to set your AWS region correctly
  http.AwsRegion := 'us-east-1';

  bucketName := 'chilkat100';
  objectName := 'starfish/starfish.jpg';
  localFilePath := 'qa_output/starfish.jpg';
  awsService := 's3';

  //  The signed URL will be valid for this number of seconds:
  numSecondsValid := 86400;

  //  Choose between a URL beginning with "http://" or "https://"...
  bUseHttps := False;

  //  Generate the pre-signed URL
  preSignedUrl := http.S3_GenPresignedUrl('GET',bUseHttps,bucketName,objectName,numSecondsValid,awsService);
  if (http.LastMethodSuccess = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  //  The following URL can be copy-and-pasted into a browser..
  WriteLn('Pre-Signed AWS S3 URL: ' + preSignedUrl);

  //  Here's an example of a pre-signed URL. 
  //  This URL will only work within 1 day (86400 seconds) after the time this example was published.
  //  
  //      http://chilkat100.s3.amazonaws.com/starfish/starfish.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=16QXXDGY83AJJR6RVQ02%2F20170111%2Fus-west-2%2Fs3%2Faws4_request&X-Amz-Date=20170111T161959Z&X-Amz-Expires=86400&X-Amz-SignedHeaders=host&X-Amz-Signature=72bf4fd9a15d7bbcdd313a3318d937a778905f62a3fbff9b789d8dc28acd9232

  //  Now try to do an HTTP Download using the signed URL.
  success := http.Download(preSignedUrl,'c:/temp/qa_output/starfish.jpg');
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  WriteLn('Success.');


  http.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.