uk.ac.horizon.artcodes.server.christmas.ImageServlet.java Source code

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Here is the source code for uk.ac.horizon.artcodes.server.christmas.ImageServlet.java

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/*
 * Artcodes recognises a different marker scheme that allows the
 * creation of aesthetically pleasing, even beautiful, codes.
 * Copyright (C) 2013-2015  The University of Nottingham
 *
 *     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 uk.ac.horizon.artcodes.server.christmas;

import com.google.appengine.tools.cloudstorage.GcsFileMetadata;
import com.google.appengine.tools.cloudstorage.GcsFileOptions;
import com.google.appengine.tools.cloudstorage.GcsFilename;
import com.google.appengine.tools.cloudstorage.GcsOutputChannel;
import com.google.appengine.tools.cloudstorage.GcsService;
import com.google.appengine.tools.cloudstorage.GcsServiceFactory;
import com.google.appengine.tools.cloudstorage.RetryParams;
import com.google.common.hash.Hashing;
import com.google.common.hash.HashingOutputStream;
import com.google.common.io.ByteStreams;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.net.URLConnection;
import java.nio.channels.Channels;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import uk.ac.horizon.artcodes.server.utils.ArtcodeServlet;
import uk.ac.horizon.artcodes.server.utils.HTTPException;

public class ImageServlet extends ArtcodeServlet {
    private static final int image_size = 512 * 1024;

    private String getImageID(HttpServletRequest req) {
        String url = req.getRequestURL().toString();
        return url.substring(url.lastIndexOf("/") + 1);
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
        doPut(request, response);
    }

    @Override
    public void doPut(HttpServletRequest request, HttpServletResponse response) throws IOException {
        try {
            if (request.getContentLength() > image_size) {
                throw new HTTPException(HttpServletResponse.SC_REQUEST_ENTITY_TOO_LARGE, "Image too large");
            }

            verifyApp(request);
            final String id = getImageID(request);
            final GcsService gcsService = GcsServiceFactory.createGcsService(RetryParams.getDefaultInstance());
            final GcsFilename filename = new GcsFilename(request.getServerName(), id);

            final GcsFileMetadata metadata = gcsService.getMetadata(filename);
            if (metadata != null) {
                throw new HTTPException(HttpServletResponse.SC_FORBIDDEN, "Cannot modify");
            }

            final BufferedInputStream inputStream = new BufferedInputStream(request.getInputStream());
            final String mimetype = URLConnection.guessContentTypeFromStream(inputStream);
            if (mimetype == null) {
                throw new HTTPException(HttpServletResponse.SC_BAD_REQUEST, "Unrecognised image type");
            }

            final GcsFileOptions.Builder fileOptionsBuilder = new GcsFileOptions.Builder();
            fileOptionsBuilder.mimeType(mimetype);
            final GcsFileOptions fileOptions = fileOptionsBuilder.build();
            final GcsOutputChannel outputChannel = gcsService.createOrReplace(filename, fileOptions);

            final HashingOutputStream outputStream = new HashingOutputStream(Hashing.sha256(),
                    Channels.newOutputStream(outputChannel));
            ByteStreams.copy(inputStream, outputStream);

            String hash = outputStream.hash().toString();
            if (!hash.equals(id)) {
                gcsService.delete(filename);
                throw new HTTPException(HttpServletResponse.SC_BAD_REQUEST, "Invalid hash");
            }

            outputStream.close();
            outputChannel.close();
        } catch (HTTPException e) {
            e.writeTo(response);
        }
    }
}