SendAllMessagesServlet.java

/*
 * Copyright 2012 Google 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 ca.grocerygo.appengine.gcm;

import com.google.appengine.api.taskqueue.Queue;
import com.google.appengine.api.taskqueue.QueueFactory;
import com.google.appengine.api.taskqueue.TaskOptions;
import com.google.appengine.api.taskqueue.TaskOptions.Method;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import static com.google.appengine.api.taskqueue.TaskOptions.Builder.withUrl;

/**
 * Servlet that adds a new message to all registered devices.
 * <p/>
 * This servlet is used just by the browser (i.e., not device).
 */
@SuppressWarnings("serial")
public class SendAllMessagesServlet extends BaseServlet {

    /**
     * Processes the request to add a new message.
     */
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws IOException, ServletException {
        List<String> devices = Datastore.getDevices();
        String status;
        if (devices.isEmpty()) {
            status = "Message ignored as there is no device registered!";
        } else {
            Queue queue = QueueFactory.getQueue("gcm");
            // NOTE: check below is for demonstration purposes; a real application
            // could always send a multicast, even for just one recipient
            if (devices.size() == 1) {
                // send a single message using plain post
                String device = devices.get(0);
                queue.add(withUrl("/send").param(
                        SendMessageServlet.PARAMETER_DEVICE, device));
                status = "Single message queued for registration id " + device;
            } else {
                // send a multicast message using JSON
                // must split in chunks of 1000 devices (GCM limit)
                int total = devices.size();
                List<String> partialDevices = new ArrayList<String>(total);
                int counter = 0;
                int tasks = 0;
                for (String device : devices) {
                    counter++;
                    partialDevices.add(device);
                    int partialSize = partialDevices.size();
                    if (partialSize == Datastore.MULTICAST_SIZE || counter == total) {
                        String multicastKey = Datastore.createMulticast(partialDevices);
                        logger.fine("Queuing " + partialSize + " devices on multicast " +
                                multicastKey);
                        TaskOptions taskOptions = TaskOptions.Builder
                                .withUrl("/send")
                                .param(SendMessageServlet.PARAMETER_MULTICAST, multicastKey)
                                .method(Method.POST);
                        queue.add(taskOptions);
                        partialDevices.clear();
                        tasks++;
                    }
                }
                status = "Queued tasks to send " + tasks + " multicast messages to " +
                        total + " devices";
            }
        }
        req.setAttribute(HomeServlet.ATTRIBUTE_STATUS, status.toString());
        getServletContext().getRequestDispatcher("/home").forward(req, resp);
    }

}