FileDownloader.java

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.security.NoSuchAlgorithmException;
import java.util.UUID;

public class FileDownloader
{

    /**
     * Creates temporary path
     *
     * @return String
     * @throws NoSuchAlgorithmException
     * @throws UnsupportedEncodingException
     */
    protected static String getDestinationPath()
    {
        String storageDirectory = System.getProperty("user.dir").concat(File.separator).concat("storage");
        File tempDirectory = new File(storageDirectory);
        if (!tempDirectory.exists()) {
            tempDirectory.mkdirs();
        }
        String temporaryFileName = UUID.randomUUID().toString();
        return storageDirectory.concat(File.separator).concat(temporaryFileName);
    }

    /**
     * Downloads external URL to destination path
     * Returns local path to downloaded URL
     *
     * @param fileUrl
     * @return String
     * @throws IOException
     * @throws NoSuchAlgorithmException
     */
    public static String download(String fileUrl) throws IOException, NoSuchAlgorithmException
    {
        return download(fileUrl, "");
    }

    /**
     * Downloads external URL to destination path
     * Returns local path to downloaded URL
     *
     * @param fileUrl
     * @return String
     * @throws IOException
     * @throws NoSuchAlgorithmException
     */
    public static String download(String fileUrl, String extension) throws IOException, NoSuchAlgorithmException
    {
        String destinationPath = getDestinationPath().concat(extension.length()>0 ? "." : "").concat(extension);
        ReadableByteChannel readableByteChannel = Channels.newChannel((new URL(fileUrl)).openStream());
        FileOutputStream fileOutputStream = new FileOutputStream(destinationPath);
        fileOutputStream.getChannel().transferFrom(readableByteChannel, 0, Long.MAX_VALUE);
        readableByteChannel.close();
        fileOutputStream.close();

        return destinationPath;
    }
}