Java tutorial
/* * 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 com.google.android.gcm.demo.server; import com.google.android.gcm.server.Constants; import com.google.android.gcm.server.Message; import com.google.android.gcm.server.MulticastResult; import com.google.android.gcm.server.Result; import com.google.android.gcm.server.Sender; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.logging.Level; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.json.simple.JSONArray; /** * Servlet that sends a message to a device. * <p> * This servlet is invoked by AppEngine's Push Queue mechanism. */ @SuppressWarnings("serial") public class SendMessageServlet extends BaseServlet { private static final String HEADER_QUEUE_COUNT = "X-AppEngine-TaskRetryCount"; private static final String HEADER_QUEUE_NAME = "X-AppEngine-QueueName"; private static final int MAX_RETRY = 3; static final String PARAMETER_DEVICE = "device"; static final String PARAMETER_MULTICAST = "multicastKey"; private Sender sender; @Override public void init(ServletConfig config) throws ServletException { super.init(config); sender = newSender(config); } /** * Creates the {@link Sender} based on the servlet settings. */ protected Sender newSender(ServletConfig config) { String key = (String) config.getServletContext().getAttribute(ApiKeyInitializer.ATTRIBUTE_ACCESS_KEY); return new Sender(key); } /** * Indicates to App Engine that this task should be retried. */ private void retryTask(HttpServletResponse resp) { resp.setStatus(500); } /** * Indicates to App Engine that this task is done. */ private void taskDone(HttpServletResponse resp) { resp.setStatus(200); } /** * Processes the request to add a new message. */ @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException { if (req.getHeader(HEADER_QUEUE_NAME) == null) { throw new IOException("Missing header " + HEADER_QUEUE_NAME); } String retryCountHeader = req.getHeader(HEADER_QUEUE_COUNT); logger.fine("retry count: " + retryCountHeader); if (retryCountHeader != null) { int retryCount = Integer.parseInt(retryCountHeader); if (retryCount > MAX_RETRY) { logger.severe("Too many retries, dropping task"); taskDone(resp); return; } } String regId = req.getParameter(PARAMETER_DEVICE); if (regId != null) { sendSingleMessage(regId, resp); return; } String multicastKey = req.getParameter(PARAMETER_MULTICAST); if (multicastKey != null) { sendMulticastMessage(multicastKey, resp); return; } logger.severe("Invalid request!"); taskDone(resp); return; } private void sendSingleMessage(String regId, HttpServletResponse resp) { logger.info("Sending message to device " + regId); Message message = new Message.Builder().addData("team", TeamGenerator.generateTeamFoosBallInJson()).build(); Result result; try { result = sender.sendNoRetry(message, regId); } catch (IOException e) { logger.log(Level.SEVERE, "Exception posting " + message, e); taskDone(resp); return; } if (result == null) { retryTask(resp); return; } if (result.getMessageId() != null) { logger.info("Succesfully sent message to device " + regId); String canonicalRegId = result.getCanonicalRegistrationId(); if (canonicalRegId != null) { // same device has more than on registration id: update it logger.finest("canonicalRegId " + canonicalRegId); Datastore.updateRegistration(regId, canonicalRegId); } } else { String error = result.getErrorCodeName(); if (error.equals(Constants.ERROR_NOT_REGISTERED)) { // application has been removed from device - unregister it Datastore.unregister(regId); } else { logger.severe("Error sending message to device " + regId + ": " + error); } } } private void sendMulticastMessage(String multicastKey, HttpServletResponse resp) { // Recover registration ids from datastore List<String> regIds = Datastore.getMulticast(multicastKey); Message message = new Message.Builder().addData("team", TeamGenerator.generateTeamFoosBallInJson()).build(); MulticastResult multicastResult; try { multicastResult = sender.sendNoRetry(message, regIds); } catch (IOException e) { logger.log(Level.SEVERE, "Exception posting " + message, e); multicastDone(resp, multicastKey); return; } boolean allDone = true; // check if any registration id must be updated if (multicastResult.getCanonicalIds() != 0) { List<Result> results = multicastResult.getResults(); for (int i = 0; i < results.size(); i++) { String canonicalRegId = results.get(i).getCanonicalRegistrationId(); if (canonicalRegId != null) { String regId = regIds.get(i); Datastore.updateRegistration(regId, canonicalRegId); } } } if (multicastResult.getFailure() != 0) { // there were failures, check if any could be retried List<Result> results = multicastResult.getResults(); List<String> retriableRegIds = new ArrayList<String>(); for (int i = 0; i < results.size(); i++) { String error = results.get(i).getErrorCodeName(); if (error != null) { String regId = regIds.get(i); logger.warning("Got error (" + error + ") for regId " + regId); if (error.equals(Constants.ERROR_NOT_REGISTERED)) { // application has been removed from device - unregister it Datastore.unregister(regId); } if (error.equals(Constants.ERROR_UNAVAILABLE)) { retriableRegIds.add(regId); } } } if (!retriableRegIds.isEmpty()) { // update task Datastore.updateMulticast(multicastKey, retriableRegIds); allDone = false; retryTask(resp); } } if (allDone) { multicastDone(resp, multicastKey); } else { retryTask(resp); } } private void multicastDone(HttpServletResponse resp, String encodedKey) { Datastore.deleteMulticast(encodedKey); taskDone(resp); } }