Triển khai hàm Lambda ImageManager

context.getLogger().log("CONTENT TYPE: " + contentType);

switch ( contentType )
{
	case "application/x-directory":
		System.out.println("application/x-directory detected - ignoring");
		break;

	case "image/jpeg":

		System.out.println("image/jpeg detected");
		InputStream objectData = null;
		objectData = response.getObjectContent();
		handleJPEG(bucket, key, objectData);
		break;

	default:
		handleAllOtherContentTypes(bucket, key);
		break;
}

private void handleJPEG(String bucketName, String key, InputStream imageStream) {

	final int THUMBNAIL_WIDTH = 100;
	final int THUMBNAIL_HEIGHT= 100;

	try
	{
		System.out.println("Starting resize process...");

		System.out.println(String.format(
				"Starting resize process for %s/%s of type image/jpg", bucketName, key));

		// Resize the image
		System.out.println("     Reading image stream from S3");
		BufferedImage image = ImageIO.read(imageStream);
		System.out.println("          done");

		final BufferedImage thumbnailImage = new BufferedImage(THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT, BufferedImage.TYPE_INT_RGB);
		final Graphics2D graphics2D = thumbnailImage.createGraphics();
		graphics2D.setComposite(AlphaComposite.Src);

		graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION,RenderingHints.VALUE_INTERPOLATION_BILINEAR);
		graphics2D.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY);
		graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

		System.out.println("     Drawing image...");
		graphics2D.drawImage(image, 0, 0, THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT, null);
		System.out.println("          done");
		graphics2D.dispose();

		System.out.println("     Opening output file...");
		File fileThumbnail = new File("/tmp/thumbnail.jpg");
		System.out.println("          done");
		System.out.println("     Writing output file...");
		ImageIO.write(thumbnailImage, "jpg", fileThumbnail);
		System.out.println("          done");

		//
		// Now put the finished object into the /processed subfolder
		// Note that the filename manipulation here is not meant to be
		// production-ready and robust! It will break if files without extensions
		// are uploaded!
		//
		String fileName = key.substring( key.lastIndexOf('/') + 1, key.length() );
		String fileNameWithoutExtn = fileName.substring(0, fileName.lastIndexOf('.'));
		System.out.println("     Pushing output file to processed folder...");
		s3.putObject(bucketName, "processed/" + fileNameWithoutExtn + ".thumb.jpg", fileThumbnail);
		System.out.println("          done");
	}
	catch(Exception e)
	{
		System.out.println(String.format(
				"Error processing JPEG image from stream for %s/%s", bucketName, key));
		System.out.println(e.getMessage());
	}
	finally
	{
		System.out.println("Ended resize");
	}
}

private void handleAllOtherContentTypes(String bucketName, String key) {

	System.out.println(String.format(
			"%s/%s is an unsupported file type. It will be deleted.", bucketName, key));

	s3.deleteObject(bucketName, key);
	System.out.println("     Done!");
}

import java.awt.AlphaComposite;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.InputStream;
import javax.imageio.ImageIO;