(Android™) S3 Resume Download

Suppose an S3 download of a very large file failed for some reason and you have a partial file on disk. Rather than restart the entire download, you wish to download the remaining portion. This example demonstrates how to finish a previously failed download.

Note: This example requires Chilkat v9.5.0.83 or above.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRest rest = new CkRest();

    // Connect to the Amazon AWS REST server.
    boolean bTls = true;
    int port = 443;
    boolean bAutoReconnect = true;
    boolean success = 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.
    CkAuthAws authAws = new CkAuthAws();
    authAws.put_AccessKey("AWS_ACCESS_KEY");
    authAws.put_SecretKey("AWS_SECRET_KEY");
    authAws.put_ServiceName("s3");
    success = rest.SetAuthAws(authAws);

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    rest.put_Host("chilkat100.s3.amazonaws.com");

    // We want to continue downloading a file.
    // The relative local filepath of our previously partially downoaded file is: qa_output/hamlet.xml
    // Let's find out how many bytes are already downloaded.
    CkFileAccess fac = new CkFileAccess();
    String localFilepath = "qa_output/hamlet.xml";
    // Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    // the size of the file as a string, then convert to an integer value.
    int sz = fac.FileSize(localFilepath);
    if (sz > 0) {
        Log.i(TAG, "sz = " + String.valueOf(sz));

        // If the sz equals 42375 bytes, then we want to add a Range header that looks like this:
        // Range: bytes=42375-
        CkStringBuilder sbRange = new CkStringBuilder();
        sbRange.Append("bytes=");
        sbRange.AppendInt(sz);
        sbRange.Append("-");
        rest.AddHeader("Range",sbRange.getAsString());
        Log.i(TAG, "Added Range: " + sbRange.getAsString());
        }

    // Send the request to download the remainder of the file.
    success = rest.SendReqNoBody("GET","/hamlet.xml");
    if (success != true) {
        Log.i(TAG, rest.lastErrorText());
        return;
        }

    // Read the response header.
    int responseStatusCode = rest.ReadResponseHeader();
    if (responseStatusCode < 0) {
        Log.i(TAG, rest.lastErrorText());
        return;
        }

    Log.i(TAG, "Response status code = " + String.valueOf(responseStatusCode));

    // We expect a 200 or 206 response status if the file data is coming.
    // Otherwise, we'll get a string response body with an error message(or no response body).
    if ((responseStatusCode == 200) or (responseStatusCode == 206)) {

        CkStream bodyStream = new CkStream();

        // The stream's sink will be a file.
        // We will append to the file..
        bodyStream.put_SinkFile(localFilepath);

        // Indicate that we wish to append to the output file.
        // The SinkFileAppend property was added in Chilkat v9.50.83
        bodyStream.put_SinkFileAppend(true);

        // 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.
        success = rest.ReadRespBodyStream(bodyStream,true);
        if (success != true) {
            Log.i(TAG, rest.lastErrorText());
            return;
            }

        Log.i(TAG, "Successfully downloaded the file.");

        }
    else {
        String errResponse = rest.readRespBodyString();
        if (rest.get_LastMethodSuccess() != true) {
            Log.i(TAG, rest.lastErrorText());
            }
        else {
            Log.i(TAG, errResponse);
            }

        }


  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}