Dart

(using AWS Signature Version 2) Streaming Download to File

See more Amazon S3 (new) Examples

The main purpose of this example is to demonstrate how to use the older Signature Version 2 authentication w/ S3. It uses V2 authentication to download 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.

  final rest = CkRest();

  // Connect to the Amazon AWS REST server.
  final bTls = true;
  final port = 443;
  final bAutoReconnect = true;
  // The file is located in the bucket named "chilkat100", which becomes part of the domain:
  rest.connect('chilkat100.s3.amazonaws.com', port, bTls, bAutoReconnect);

  // Provide AWS credentials for the REST call.
  final authAws = CkAuthAws();
  authAws.accessKey = 'AWS_ACCESS_KEY';
  authAws.secretKey = 'AWS_SECRET_KEY';
  authAws.serviceName = 's3';

  // For AWS Signature Version 2, the following two properties need to be set:
  authAws.signatureVersion = 2;
  // See http://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentication.html#ConstructingTheCanonicalizedResourceElement
  authAws.canonicalizedResourceV2 = '/chilkat100/starfish.jpg';

  rest.setAuthAws(authAws);

  // Send the request to download the JPG.
  try {
    rest.sendReqNoBody('GET', '/starfish.jpg');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Read the response header.
  final responseStatusCode = rest.readResponseHeader();
  if (responseStatusCode < 0) {
    print(rest.lastErrorText);
    return;
  }

  print('Response status code = $responseStatusCode');

  // We expect a 200 response status if the JPG data is coming.
  // Otherwise, we'll get a string response body with an error message(or no response body).
  if (responseStatusCode == 200) {

    final bodyStream = CkStream();

    // The stream's sink will be a file.
    bodyStream.sinkFile = 'qa_output/starfish.jpg';

    // Read the response body to the stream.  Given that we've
    // set the stream's sink to a file, it will stream directly
    // to the file.
    try {
      rest.readRespBodyStream(bodyStream, true);
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
      return;
    }

    print('Successfully received the JPG file.');
  } else {
    try {
      final errResponse = rest.readRespBodyString();
      print(errResponse);
    } on ChilkatException catch (e) {
      print(e.lastErrorText);
    }
  }
}