getDownloadURL method

Future<String> getDownloadURL(Bucket bucket, String objectName)

Returns a long-lived download URL for the given object.

The URL is signed with a download token from the Firebase Storage REST API, making it suitable for sharing with end-users. The token must exist on the object — if none is present, create one in the Firebase Console or via the Firebase Storage REST API first.

Example:

final storage = app.storage();
final bucket = storage.bucket('my-bucket.appspot.com');
final url = await storage.getDownloadURL(bucket, 'images/photo.jpg');

Implementation

Future<String> getDownloadURL(gcs.Bucket bucket, String objectName) async {
  final emulatorHost = Environment.getStorageEmulatorHost();
  final endpoint = emulatorHost != null
      ? 'http://$emulatorHost/v0'
      : 'https://firebasestorage.googleapis.com/v0';

  final encodedName = Uri.encodeComponent(objectName);
  final uri = Uri.parse('$endpoint/b/${bucket.name}/o/$encodedName');

  final client = await app.client;
  final response = await client.get(uri);

  if (response.statusCode != 200) {
    throw FirebaseStorageAdminException(
      StorageClientErrorCode.internalError,
      'Failed to retrieve object metadata. Status: ${response.statusCode}.',
    );
  }

  final json = jsonDecode(response.body) as Map<String, dynamic>;
  final downloadTokens = json['downloadTokens'] as String?;

  if (downloadTokens == null || downloadTokens.isEmpty) {
    throw FirebaseStorageAdminException(
      StorageClientErrorCode.noDownloadToken,
    );
  }

  final token = downloadTokens.split(',').first;
  return '$endpoint/b/${bucket.name}/o/$encodedName?alt=media&token=$token';
}