Pascal (Lazarus/Delphi)

Download Object from Google Cloud Storage

See more Google Cloud Storage Examples

Demonstrates how to download an object from Google Cloud Storage to a file. 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,
  Chilkat.StringBuilder,
  Chilkat.BinData;

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

procedure RunDemo;
var
  success: Boolean;
  sbToken: TStringBuilder;
  http: THttp;
  url: string;
  fileData: TBinData;
  sbErrorResponse: TStringBuilder;
  responseCode: Integer;

begin
  success := False;

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

  //  This example uses a previously obtained access token having permission for the 
  //  scope "https://www.googleapis.com/auth/cloud-platform"

  //  In this example, Get Google Cloud Storage OAuth2 Access Token, 
  //  the service account access token was saved to a text file.  This example fetches the access token from the file..
  sbToken := TStringBuilder.Create;
  sbToken.LoadFile('qa_data/tokens/googleCloudStorageAccessToken.txt','utf-8');

  //  Send a GET equivalent to this curl command.

  //  curl -X GET \
  //      -H "Authorization: Bearer [OAUTH2_TOKEN]" \
  //      -o "[SAVE_TO_LOCATION]" \
  //      "https://www.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/[OBJECT_NAME]?alt=media"

  http := THttp.Create;

  http.AuthToken := sbToken.GetAsString();

  //  Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
  http.SetUrlVar('bucket_name','chilkat-ocean');
  http.SetUrlVar('object_name','starfish.jpg');
  url := 'https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media';

  //  If there is an error response, then we didn't actually download the file data,
  //  but instead we downloaded an error response..
  fileData := TBinData.Create;
  success := http.DownloadBd(url,fileData);
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  sbErrorResponse := TStringBuilder.Create;
  responseCode := http.LastStatus;
  if (responseCode = 401) then
    begin
      WriteLn('If invalid credentials, then it is likely the access token expired.');
      WriteLn('Your app should automatically fetch a new access token and re-try.');
    end;

  if (responseCode <> 200) then
    begin
      //  Get the error response
      sbErrorResponse.AppendBd(fileData,'utf-8',0,0);
      WriteLn('Error response code = ' + responseCode);
      WriteLn('Error:');
      WriteLn(sbErrorResponse.GetAsString());
      Exit;
    end;

  WriteLn('Success.');

  //  Save the downloaded data to a file.
  success := fileData.WriteFile('qa_output/starfish.jpg');


  sbToken.Free;
  http.Free;
  fileData.Free;
  sbErrorResponse.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.