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Java example source code file (S3Downloader.java)

This example Java source code file (S3Downloader.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

amazons3, arraylist, bufferedoutputstream, fileoutputstream, inputstream, ioexception, list, listobjectsrequest, objectlisting, s3downloader, s3object, s3objectsummary, string, transfermanager, util

The S3Downloader.java Java example source code

/*
 *
 *  * Copyright 2015 Skymind,Inc.
 *  *
 *  *    Licensed under the Apache License, Version 2.0 (the "License");
 *  *    you may not use this file except in compliance with the License.
 *  *    You may obtain a copy of the License at
 *  *
 *  *        http://www.apache.org/licenses/LICENSE-2.0
 *  *
 *  *    Unless required by applicable law or agreed to in writing, software
 *  *    distributed under the License is distributed on an "AS IS" BASIS,
 *  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  *    See the License for the specific language governing permissions and
 *  *    limitations under the License.
 *
 */

package org.deeplearning4j.aws.s3.reader;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.amazonaws.services.s3.model.*;
import com.amazonaws.services.s3.transfer.MultipleFileDownload;
import com.amazonaws.services.s3.transfer.TransferManager;
import org.apache.commons.io.IOUtils;
import org.deeplearning4j.aws.s3.BaseS3;

import com.amazonaws.services.s3.AmazonS3;

/**
 * Downloads files from S3
 * @author Adam Gibson
 *
 */
public class S3Downloader extends BaseS3 {


    /**
     * Return the keys for a bucket
     * @param bucket the bucket to get the keys for
     * @return the bucket's keys
     */
    public List<String> keysForBucket(String bucket) {
        AmazonS3 s3 = getClient();
        List<String> ret = new ArrayList<>();
        ListObjectsRequest listObjectsRequest = new ListObjectsRequest()
                .withBucketName(bucket);
        ObjectListing objectListing;

        do {
            objectListing = s3.listObjects(listObjectsRequest);
            for (S3ObjectSummary objectSummary :  objectListing.getObjectSummaries()) {
                ret.add(objectSummary.getKey());
            }
            listObjectsRequest.setMarker(objectListing.getNextMarker());
        } while (objectListing.isTruncated());

        return ret;
    }

	/**
	 * Returns the list of buckets in s3
	 * @return the list of buckets
	 */
	public List<String> buckets() {
		List<String> ret = new ArrayList<>();
		AmazonS3 s3 = getClient();
		List<Bucket> buckets = s3.listBuckets();
		for(Bucket b : buckets)
			ret.add(b.getName());
		return ret;
	}
	
	/**
	 * Iterate over individual buckets.
	 * Returns input streams to each object.
	 * It is your responsibility to close the input streams
	 * @param bucket the bucket to iterate over
	 * @return an iterator over the objects in an s3 bucket
	 */
	public Iterator<InputStream> iterateBucket(String bucket) {
		return new BucketIterator(bucket,this);
	}

	/**
	 * Iterator style one list at a time
	 * @param list the list to getFromOrigin the next batch for
	 * @return the next batch of objects or null if
	 * none are left
	 */
	public ObjectListing nextList(ObjectListing list) {
		AmazonS3 s3 = getClient();
		if(list.isTruncated())
			return s3.listNextBatchOfObjects(list);
		return null;
	}

	/**
	 * Simple way of retrieving the listings for a bucket
	 * @param bucket the bucket to retrieve listings for
	 * @return the object listing for this bucket
	 */
	public ObjectListing listObjects(String bucket) {
		AmazonS3 s3 = getClient();
		ObjectListing list = s3.listObjects(bucket);
		return list;
	}

	/**
	 * Paginates through a bucket's keys invoking the listener 
	 * at each key
	 * @param bucket the bucket to iterate
	 * @param listener the listener
	 */
	public void paginate(String bucket,BucketKeyListener listener) {
		AmazonS3 s3 = getClient();
		ObjectListing list = s3.listObjects(bucket);
		for(S3ObjectSummary summary : list.getObjectSummaries()) {
			if(listener != null)
				listener.onKey(s3, bucket, summary.getKey());
		}

		while(list.isTruncated()) {
			list = s3.listNextBatchOfObjects(list);
			for(S3ObjectSummary summary : list.getObjectSummaries()) {
				if(listener != null)
					listener.onKey(s3, bucket, summary.getKey());
			}
		}


	}


	/**
	 * Returns an input stream for the given bucket and key
	 * @param bucket the bucket to retrieve from
	 * @param key the key of the objec  t
	 * @return an input stream to the object
	 */
	public InputStream objectForKey(String bucket,String key) {
		AmazonS3 s3 = getClient();
		S3Object obj = s3.getObject(bucket, key);
		InputStream is = obj.getObjectContent();
		return is;
	}


	public void download(String bucket,String key,File to) throws IOException {
		AmazonS3 s3 = getClient();
		S3Object obj = s3.getObject(bucket, key);
		InputStream is = obj.getObjectContent();
		BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(to));
		IOUtils.copy(is, bos);
		bos.close();
		is.close();
		obj.close();
	}

	public void download(String bucket,String key,OutputStream to) throws IOException {
		AmazonS3 s3 = getClient();
		S3Object obj = s3.getObject(bucket, key);
		InputStream is = obj.getObjectContent();
		BufferedOutputStream bos = new BufferedOutputStream(to);

		IOUtils.copy(is, bos);
		bos.close();
		is.close();
		obj.close();
	}

	public MultipleFileDownload downloadFolder(String bucketName, String keyPrefix, File folderPath) {
		TransferManager transfer = new TransferManager(getClient());
		return transfer.downloadDirectory(bucketName, keyPrefix, folderPath);
	}


}

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