Dart

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. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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..
  final sbToken = CkStringBuilder();
  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"

  final http = CkHttp();

  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');
  final 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..
  final fileData = CkBinData();
  try {
    http.downloadBd(url, fileData);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final sbErrorResponse = CkStringBuilder();
  final responseCode = http.lastStatus;
  if (responseCode == 401) {
    print('If invalid credentials, then it is likely the access token expired.');
    print('Your app should automatically fetch a new access token and re-try.');
  }

  if (responseCode != 200) {
    // Get the error response
    sbErrorResponse.appendBd(fileData, 'utf-8', 0, 0);
    print('Error response code = $responseCode');
    print('Error:');
    print(sbErrorResponse.getAsString());
    return;
  }

  print('Success.');

  // Save the downloaded data to a file.
  fileData.writeFile('qa_output/starfish.jpg');
}