DatastoreAdapter.java

/*
 * Copyright (c) 2006-2009 by Dirk Riehle, http://dirkriehle.com
 *
 * This file is part of the Wahlzeit photo rating application.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this program. If not, see
 * <http://www.gnu.org/licenses/>.
 */

package org.wahlzeit.model.persistence;

import com.google.appengine.api.images.Image;
import com.google.appengine.api.images.ImagesServiceFactory;
import com.googlecode.objectify.ObjectifyService;
import com.googlecode.objectify.Work;
import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Id;
import org.wahlzeit.services.LogBuilder;
import org.wahlzeit.services.OfyService;

import java.io.IOException;
import java.io.Serializable;
import java.security.InvalidParameterException;
import java.util.logging.Logger;

/**
 * Adapter for the Google Datastore. Use default constructor to create an instance.
 * 
 * @review
 */
public class DatastoreAdapter extends ImageStorage {

	private static final Logger log = Logger.getLogger(DatastoreAdapter.class.getName());


	@Override
	protected void doWriteImage(Serializable image, String photoIdAsString, int size)
			throws IOException, InvalidParameterException {
		if (image instanceof Image) {
			final ImageWrapper imageWrapper = new ImageWrapper(photoIdAsString + size);
			imageWrapper.setImage((Image) image);

			ObjectifyService.run(new Work<Boolean>() {
				@Override
				public Boolean run() {
					OfyService.ofy().save().entity(imageWrapper).now();
					return null;
				}
			});

			log.config(LogBuilder.createSystemMessage().addMessage("image successfully written").toString());
		} else {
			log.warning(LogBuilder.createSystemMessage().
					addMessage("did not get an Image type to store").
					addParameter("image type", image.toString()).toString());
		}
	}

	@Override
	protected Image doReadImage(final String photoIdAsString, final int size) throws IOException {
		Image result = null;

		ImageWrapper imageWrapper = ObjectifyService.run(new Work<ImageWrapper>() {
			@Override
			public ImageWrapper run() {
				return OfyService.ofy().load().type(ImageWrapper.class).id(photoIdAsString + size).now();
			}
		});

		if (imageWrapper == null) {
			log.info(LogBuilder.createSystemMessage().addMessage("does not exist!").toString());
		} else {
			result = imageWrapper.getImage();
			if (result != null) {
				log.config(LogBuilder.createSystemMessage().addMessage("image successfully read").toString());
			} else {
				log.warning(LogBuilder.createSystemMessage().addMessage("ImageWrapper contains no Image").toString());
			}
		}
		return result;
	}

	@Override
	protected boolean doDoesImageExist(String photoIdAsString, int size) {
		Image image = null;
		boolean result = false;
		try {
			image = doReadImage(photoIdAsString, size);
		} catch (IOException e) {
			log.warning(
					LogBuilder.createSystemMessage().addException("IOException when checking for Image existance", e)
							.toString());
		}
		if (image != null) {
			result = true;
		}
		log.config(LogBuilder.createSystemMessage().addParameter("does image exist", result).toString());
		return result;
	}

	/**
	 * Wrapper class to store {@link Image}s in the Google Datastore with Objectify.
	 * 
 	 * @review
	 */
	@Entity
	public static class ImageWrapper {

		// see https://cloud.google.com/datastore/docs/tools/administration
		public final int maxEntitySize = 1024 * 1024; // = 1 MB

		@Id
		private String id;

		private byte[] imageData;

		public ImageWrapper() {
			// just for Objectify to load it from Datastore
		}

		public ImageWrapper(String id) {
			this.id = id;
		}

		/**
		 * @methodtype get
		 */
		public Image getImage() {
			return ImagesServiceFactory.makeImage(imageData);
		}

		/**
		 * @methodtype set
		 *
		 * Can not handle images >= 1 MB because this is the upper limit of entities in Google Datastore.
		 */
		public void setImage(Image image) throws ArrayIndexOutOfBoundsException {
			if(image.getImageData().length >= maxEntitySize) {
				throw new ArrayIndexOutOfBoundsException("Can not store images >= 1 MB in the Google Datastore.");
			}
			else {
				imageData = image.getImageData();
			}
		}
	}
}