Dart

REST Stream Response to File (Streaming Download) (Amazon S3)

See more Amazon S3 (new) Examples

Demonstrates how to stream the response body directly to a file. (The example shows how to stream a JPG from the Amazon S3 service.) 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;
  rest.connect('s3.amazonaws.com', port, bTls, bAutoReconnect);

  // ----------------------------------------------------------------------------
  // Important: For buckets created in regions outside us-east-1,
  // there are three important changes that need to be made.
  // See Working with S3 Buckets in Non-us-east-1 Regions for the details.
  // ----------------------------------------------------------------------------

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

  // Set the bucket name via the HOST header.
  // In this case, the bucket name is "chilkat100".
  rest.host = 'chilkat100.s3.amazonaws.com';

  // 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);
    }
  }
}