(Delphi ActiveX) Download Object from Google Cloud Storage

Demonstrates how to download an object from Google Cloud Storage to a file.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
sbToken: TChilkatStringBuilder;
http: TChilkatHttp;
url: WideString;
fileData: TChilkatBinData;
success: Integer;
sbErrorResponse: TChilkatStringBuilder;
responseCode: Integer;

begin
// 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 := TChilkatStringBuilder.Create(Self);
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 := TChilkatHttp.Create(Self);

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 := TChilkatBinData.Create(Self);
success := http.DownloadBd(url,fileData.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

sbErrorResponse := TChilkatStringBuilder.Create(Self);
responseCode := http.LastStatus;
if (responseCode = 401) then
  begin
    Memo1.Lines.Add('If invalid credentials, then it is likely the access token expired.');
    Memo1.Lines.Add('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.ControlInterface,'utf-8',0,0);
    Memo1.Lines.Add('Error response code = ' + IntToStr(responseCode));
    Memo1.Lines.Add('Error:');
    Memo1.Lines.Add(sbErrorResponse.GetAsString());
    Exit;
  end;

Memo1.Lines.Add('Success.');

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