Dart

Azure Blob - Get Tags (Check if Blob Exists)

See more Azure Cloud Storage Examples

Gets the user-defined tags for a specified blob. This can also be used as a way to check to see if a blob exists. 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.

  final rest = CkRest();

  // Connect to the Azure Storage Blob Service
  final bTls = true;
  final port = 443;
  final bAutoReconnect = true;
  // In this example, the storage account name is "chilkat".
  try {
    rest.connect('chilkat.blob.core.windows.net', port, bTls, bAutoReconnect);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Provide Azure Cloud credentials for the REST call.
  final azAuth = CkAuthAzureStorage();
  azAuth.accessKey = 'AZURE_ACCESS_KEY';
  // The account name used here should match the 1st part of the domain passed in the call to Connect (above).
  azAuth.account = 'chilkat';
  azAuth.scheme = 'SharedKey';
  azAuth.service = 'Blob';
  // This causes the "x-ms-version: 2021-08-06" header to be automatically added.
  azAuth.xMsVersion = '2021-08-06';
  rest.setAuthAzureStorage(azAuth);

  // Note: The application does not need to explicitly set the following
  // headers: Content-Length, x-ms-date, Authorization.  These headers
  // are automatically set by Chilkat.

  // The Azure blob container is "test", the file is "helloWorld.txt"
  // Add "?comp=tags" to get the user-defined tags instead of the actual blob content.
  final sb = CkStringBuilder();
  try {
    rest.fullRequestNoBodySb('GET', '/test/helloWorldajdfadf.txt?comp=tags', sb);
  } on ChilkatException {
    // Examine the request/response to see what happened.
    print('response status code = ${rest.responseStatusCode}');
    print('response status text = ${rest.responseStatusText}');
    print('response header: ${rest.responseHeader}');
    print('---');
    print('LastRequestStartLine: ${rest.lastRequestStartLine}');
    print('LastRequestHeader: ${rest.lastRequestHeader}');
    return;
  }

  // A typical blob with no tags will return this:

  // <?xml version="1.0" encoding="utf-8"?>
  // <Tags><TagSet/></Tags>

  // If the blob does not exist, you get this:

  // <?xml version="1.0" encoding="utf-8"?>
  // <Error>
  //     <Code>BlobNotFound</Code>
  //     <Message>The specified blob does not exist.
  // 	RequestId:fcfefdd9-301e-001a-2135-3a23d2000000
  // 	Time:2023-02-06T14:17:00.7805577Z
  //     </Message>
  // </Error>

  print(sb.getAsString());

  // To see if we got Tags or an Error, then examine the XML.
  final xml = CkXml();
  xml.loadSb(sb, true);

  // Examine the tag..
  if (xml.tagEquals('Tags')) {
    print('Blob exists!');
  } else {

    if (xml.childContentMatches('Code', 'BlobNotFound', true)) {
      print('Blob does not exist.');
    } else {
      print('Some other error...');
    }
  }

  print('Success.');
}