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 ccs_server; import static ccs_server.Constants.GCM_SEND_ENDPOINT; import static ccs_server.Constants.JSON_CANONICAL_IDS; import static ccs_server.Constants.JSON_ERROR; import static ccs_server.Constants.JSON_FAILURE; import static ccs_server.Constants.JSON_MESSAGE_ID; import static ccs_server.Constants.JSON_MULTICAST_ID; import static ccs_server.Constants.JSON_PAYLOAD; import static ccs_server.Constants.JSON_REGISTRATION_IDS; import static ccs_server.Constants.JSON_RESULTS; import static ccs_server.Constants.JSON_SUCCESS; import static ccs_server.Constants.PARAM_COLLAPSE_KEY; import static ccs_server.Constants.PARAM_DELAY_WHILE_IDLE; import static ccs_server.Constants.PARAM_DRY_RUN; import static ccs_server.Constants.PARAM_PAYLOAD_PREFIX; import static ccs_server.Constants.PARAM_REGISTRATION_ID; import static ccs_server.Constants.PARAM_RESTRICTED_PACKAGE_NAME; import static ccs_server.Constants.PARAM_TIME_TO_LIVE; import static ccs_server.Constants.TOKEN_CANONICAL_REG_ID; import static ccs_server.Constants.TOKEN_ERROR; import static ccs_server.Constants.TOKEN_MESSAGE_ID; import ccs_server.Result.Builder; import org.json.simple.JSONObject; import org.json.simple.JSONValue; import org.json.simple.parser.JSONParser; import org.json.simple.parser.ParseException; import java.io.BufferedReader; import java.io.Closeable; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLEncoder; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Random; import java.util.logging.Level; import java.util.logging.Logger; /** * Helper class to send messages to the GCM service using an API Key. */ public class Sender { protected static final String UTF8 = "UTF-8"; /** * Initial delay before first retry, without jitter. */ protected static final int BACKOFF_INITIAL_DELAY = 1000; /** * Maximum delay before a retry. */ protected static final int MAX_BACKOFF_DELAY = 1024000; protected final Random random = new Random(); protected static final Logger logger = Logger.getLogger(Sender.class.getName()); private final String key; /** * Default constructor. * * @param key API key obtained through the Google API Console. */ public Sender(String key) { this.key = nonNull(key); } /** * Sends a message to one device, retrying in case of unavailability. * * <p> * <strong>Note: </strong> this method uses exponential back-off to retry in * case of service unavailability and hence could block the calling thread * for many seconds. * * @param message message to be sent, including the device's registration id. * @param registrationId device where the message will be sent. * @param retries number of retries in case of service unavailability errors. * * @return result of the request (see its javadoc for more details). * * @throws IllegalArgumentException if registrationId is {@literal null}. * @throws InvalidRequestException if GCM didn't returned a 200 or 5xx status. * @throws IOException if message could not be sent. */ public Result send(Message message, String registrationId, int retries) throws IOException { int attempt = 0; Result result = null; int backoff = BACKOFF_INITIAL_DELAY; boolean tryAgain; do { attempt++; if (logger.isLoggable(Level.FINE)) { logger.fine("Attempt #" + attempt + " to send message " + message + " to regIds " + registrationId); } result = sendNoRetry(message, registrationId); tryAgain = result == null && attempt <= retries; if (tryAgain) { int sleepTime = backoff / 2 + random.nextInt(backoff); sleep(sleepTime); if (2 * backoff < MAX_BACKOFF_DELAY) { backoff *= 2; } } } while (tryAgain); if (result == null) { throw new IOException("Could not send message after " + attempt + " attempts"); } return result; } /** * Sends a message without retrying in case of service unavailability. See * {@link #send(Message, String, int)} for more info. * * @return result of the post, or {@literal null} if the GCM service was * unavailable or any network exception caused the request to fail. * * @throws InvalidRequestException if GCM didn't returned a 200 or 5xx status. * @throws IllegalArgumentException if registrationId is {@literal null}. */ public Result sendNoRetry(Message message, String registrationId) throws IOException { StringBuilder body = newBody(PARAM_REGISTRATION_ID, registrationId); Boolean delayWhileIdle = message.isDelayWhileIdle(); if (delayWhileIdle != null) { addParameter(body, PARAM_DELAY_WHILE_IDLE, delayWhileIdle ? "1" : "0"); } Boolean dryRun = message.isDryRun(); if (dryRun != null) { addParameter(body, PARAM_DRY_RUN, dryRun ? "1" : "0"); } String collapseKey = message.getCollapseKey(); if (collapseKey != null) { addParameter(body, PARAM_COLLAPSE_KEY, collapseKey); } String restrictedPackageName = message.getRestrictedPackageName(); if (restrictedPackageName != null) { addParameter(body, PARAM_RESTRICTED_PACKAGE_NAME, restrictedPackageName); } Integer timeToLive = message.getTimeToLive(); if (timeToLive != null) { addParameter(body, PARAM_TIME_TO_LIVE, Integer.toString(timeToLive)); } for (Entry<String, String> entry : message.getData().entrySet()) { String key = entry.getKey(); String value = entry.getValue(); if (key == null || value == null) { logger.warning("Ignoring payload entry thas has null: " + entry); } else { key = PARAM_PAYLOAD_PREFIX + key; addParameter(body, key, URLEncoder.encode(value, UTF8)); } } String requestBody = body.toString(); logger.finest("Request body: " + requestBody); HttpURLConnection conn; int status; try { conn = post(GCM_SEND_ENDPOINT, requestBody); status = conn.getResponseCode(); } catch (IOException e) { logger.log(Level.FINE, "IOException posting to GCM", e); return null; } if (status / 100 == 5) { logger.fine("GCM service is unavailable (status " + status + ")"); return null; } String responseBody; if (status != 200) { try { responseBody = getAndClose(conn.getErrorStream()); logger.finest("Plain post error response: " + responseBody); } catch (IOException e) { // ignore the exception since it will thrown an InvalidRequestException // anyways responseBody = "N/A"; logger.log(Level.FINE, "Exception reading response: ", e); } throw new InvalidRequestException(status, responseBody); } else { try { responseBody = getAndClose(conn.getInputStream()); } catch (IOException e) { logger.log(Level.WARNING, "Exception reading response: ", e); // return null so it can retry return null; } } String[] lines = responseBody.split("\n"); if (lines.length == 0 || lines[0].equals("")) { throw new IOException("Received empty response from GCM service."); } String firstLine = lines[0]; String[] responseParts = split(firstLine); String token = responseParts[0]; String value = responseParts[1]; if (token.equals(TOKEN_MESSAGE_ID)) { Builder builder = new Result.Builder().messageId(value); // check for canonical registration id if (lines.length > 1) { String secondLine = lines[1]; responseParts = split(secondLine); token = responseParts[0]; value = responseParts[1]; if (token.equals(TOKEN_CANONICAL_REG_ID)) { builder.canonicalRegistrationId(value); } else { logger.warning("Invalid response from GCM: " + responseBody); } } Result result = builder.build(); if (logger.isLoggable(Level.FINE)) { logger.fine("Message created succesfully (" + result + ")"); } return result; } else if (token.equals(TOKEN_ERROR)) { return new Result.Builder().errorCode(value).build(); } else { throw new IOException("Invalid response from GCM: " + responseBody); } } /** * Sends a message to many devices, retrying in case of unavailability. * * <p> * <strong>Note: </strong> this method uses exponential back-off to retry in * case of service unavailability and hence could block the calling thread * for many seconds. * * @param message message to be sent. * @param regIds registration id of the devices that will receive * the message. * @param retries number of retries in case of service unavailability errors. * * @return combined result of all requests made. * * @throws IllegalArgumentException if registrationIds is {@literal null} or * empty. * @throws InvalidRequestException if GCM didn't returned a 200 or 503 status. * @throws IOException if message could not be sent. */ public MulticastResult send(Message message, List<String> regIds, int retries) throws IOException { int attempt = 0; MulticastResult multicastResult; int backoff = BACKOFF_INITIAL_DELAY; // Map of results by registration id, it will be updated after each attempt // to send the messages Map<String, Result> results = new HashMap<String, Result>(); List<String> unsentRegIds = new ArrayList<String>(regIds); boolean tryAgain; List<Long> multicastIds = new ArrayList<Long>(); do { multicastResult = null; attempt++; if (logger.isLoggable(Level.FINE)) { logger.fine("Attempt #" + attempt + " to send message " + message + " to regIds " + unsentRegIds); } try { multicastResult = sendNoRetry(message, unsentRegIds); } catch (IOException e) { // no need for WARNING since exception might be already logged logger.log(Level.FINEST, "IOException on attempt " + attempt, e); } if (multicastResult != null) { long multicastId = multicastResult.getMulticastId(); logger.fine("multicast_id on attempt # " + attempt + ": " + multicastId); multicastIds.add(multicastId); unsentRegIds = updateStatus(unsentRegIds, results, multicastResult); tryAgain = !unsentRegIds.isEmpty() && attempt <= retries; } else { tryAgain = attempt <= retries; } if (tryAgain) { int sleepTime = backoff / 2 + random.nextInt(backoff); sleep(sleepTime); if (2 * backoff < MAX_BACKOFF_DELAY) { backoff *= 2; } } } while (tryAgain); if (multicastIds.isEmpty()) { // all JSON posts failed due to GCM unavailability throw new IOException("Could not post JSON requests to GCM after " + attempt + " attempts"); } // calculate summary int success = 0, failure = 0, canonicalIds = 0; for (Result result : results.values()) { if (result.getMessageId() != null) { success++; if (result.getCanonicalRegistrationId() != null) { canonicalIds++; } } else { failure++; } } // build a new object with the overall result long multicastId = multicastIds.remove(0); MulticastResult.Builder builder = new MulticastResult.Builder(success, failure, canonicalIds, multicastId) .retryMulticastIds(multicastIds); // add results, in the same order as the input for (String regId : regIds) { Result result = results.get(regId); builder.addResult(result); } return builder.build(); } /** * Updates the status of the messages sent to devices and the list of devices * that should be retried. * * @param unsentRegIds list of devices that are still pending an update. * @param allResults map of status that will be updated. * @param multicastResult result of the last multicast sent. * * @return updated version of devices that should be retried. */ private List<String> updateStatus(List<String> unsentRegIds, Map<String, Result> allResults, MulticastResult multicastResult) { List<Result> results = multicastResult.getResults(); if (results.size() != unsentRegIds.size()) { // should never happen, unless there is a flaw in the algorithm throw new RuntimeException("Internal error: sizes do not match. " + "currentResults: " + results + "; unsentRegIds: " + unsentRegIds); } List<String> newUnsentRegIds = new ArrayList<String>(); for (int i = 0; i < unsentRegIds.size(); i++) { String regId = unsentRegIds.get(i); Result result = results.get(i); allResults.put(regId, result); String error = result.getErrorCodeName(); if (error != null && (error.equals(Constants.ERROR_UNAVAILABLE) || error.equals(Constants.ERROR_INTERNAL_SERVER_ERROR))) { newUnsentRegIds.add(regId); } } return newUnsentRegIds; } /** * Sends a message without retrying in case of service unavailability. See * {@link #send(Message, List, int)} for more info. * * @return multicast results if the message was sent successfully, * {@literal null} if it failed but could be retried. * * @throws IllegalArgumentException if registrationIds is {@literal null} or * empty. * @throws InvalidRequestException if GCM didn't returned a 200 status. * @throws IOException if there was a JSON parsing error */ public MulticastResult sendNoRetry(Message message, List<String> registrationIds) throws IOException { if (nonNull(registrationIds).isEmpty()) { throw new IllegalArgumentException("registrationIds cannot be empty"); } Map<Object, Object> jsonRequest = new HashMap<Object, Object>(); setJsonField(jsonRequest, PARAM_TIME_TO_LIVE, message.getTimeToLive()); setJsonField(jsonRequest, PARAM_COLLAPSE_KEY, message.getCollapseKey()); setJsonField(jsonRequest, PARAM_RESTRICTED_PACKAGE_NAME, message.getRestrictedPackageName()); setJsonField(jsonRequest, PARAM_DELAY_WHILE_IDLE, message.isDelayWhileIdle()); setJsonField(jsonRequest, PARAM_DRY_RUN, message.isDryRun()); jsonRequest.put(JSON_REGISTRATION_IDS, registrationIds); Map<String, String> payload = message.getData(); if (!payload.isEmpty()) { jsonRequest.put(JSON_PAYLOAD, payload); } String requestBody = JSONValue.toJSONString(jsonRequest); logger.finest("JSON request: " + requestBody); HttpURLConnection conn; int status; try { conn = post(GCM_SEND_ENDPOINT, "application/json", requestBody); status = conn.getResponseCode(); } catch (IOException e) { logger.log(Level.FINE, "IOException posting to GCM", e); return null; } String responseBody; if (status != 200) { try { responseBody = getAndClose(conn.getErrorStream()); logger.finest("JSON error response: " + responseBody); } catch (IOException e) { // ignore the exception since it will thrown an InvalidRequestException // anyways responseBody = "N/A"; logger.log(Level.FINE, "Exception reading response: ", e); } throw new InvalidRequestException(status, responseBody); } try { responseBody = getAndClose(conn.getInputStream()); } catch (IOException e) { logger.log(Level.WARNING, "IOException reading response", e); return null; } logger.finest("JSON response: " + responseBody); JSONParser parser = new JSONParser(); JSONObject jsonResponse; try { jsonResponse = (JSONObject) parser.parse(responseBody); int success = getNumber(jsonResponse, JSON_SUCCESS).intValue(); int failure = getNumber(jsonResponse, JSON_FAILURE).intValue(); int canonicalIds = getNumber(jsonResponse, JSON_CANONICAL_IDS).intValue(); long multicastId = getNumber(jsonResponse, JSON_MULTICAST_ID).longValue(); MulticastResult.Builder builder = new MulticastResult.Builder(success, failure, canonicalIds, multicastId); @SuppressWarnings("unchecked") List<Map<String, Object>> results = (List<Map<String, Object>>) jsonResponse.get(JSON_RESULTS); if (results != null) { for (Map<String, Object> jsonResult : results) { String messageId = (String) jsonResult.get(JSON_MESSAGE_ID); String canonicalRegId = (String) jsonResult.get(TOKEN_CANONICAL_REG_ID); String error = (String) jsonResult.get(JSON_ERROR); Result result = new Result.Builder().messageId(messageId) .canonicalRegistrationId(canonicalRegId).errorCode(error).build(); builder.addResult(result); } } MulticastResult multicastResult = builder.build(); return multicastResult; } catch (ParseException e) { throw newIoException(responseBody, e); } catch (CustomParserException e) { throw newIoException(responseBody, e); } } private IOException newIoException(String responseBody, Exception e) { // log exception, as IOException constructor that takes a message and cause // is only available on Java 6 String msg = "Error parsing JSON response (" + responseBody + ")"; logger.log(Level.WARNING, msg, e); return new IOException(msg + ":" + e); } private static void close(Closeable closeable) { if (closeable != null) { try { closeable.close(); } catch (IOException e) { // ignore error logger.log(Level.FINEST, "IOException closing stream", e); } } } /** * Sets a JSON field, but only if the value is not {@literal null}. */ private void setJsonField(Map<Object, Object> json, String field, Object value) { if (value != null) { json.put(field, value); } } private Number getNumber(Map<?, ?> json, String field) { Object value = json.get(field); if (value == null) { throw new CustomParserException("Missing field: " + field); } if (!(value instanceof Number)) { throw new CustomParserException("Field " + field + " does not contain a number: " + value); } return (Number) value; } class CustomParserException extends RuntimeException { CustomParserException(String message) { super(message); } } private String[] split(String line) throws IOException { String[] split = line.split("=", 2); if (split.length != 2) { throw new IOException("Received invalid response line from GCM: " + line); } return split; } /** * Make an HTTP post to a given URL. * * @return HTTP response. */ protected HttpURLConnection post(String url, String body) throws IOException { return post(url, "application/x-www-form-urlencoded;charset=UTF-8", body); } /** * Makes an HTTP POST request to a given endpoint. * * <p> * <strong>Note: </strong> the returned connected should not be disconnected, * otherwise it would kill persistent connections made using Keep-Alive. * * @param url endpoint to post the request. * @param contentType type of request. * @param body body of the request. * * @return the underlying connection. * * @throws IOException propagated from underlying methods. */ protected HttpURLConnection post(String url, String contentType, String body) throws IOException { if (url == null || body == null) { throw new IllegalArgumentException("arguments cannot be null"); } if (!url.startsWith("https://")) { logger.warning("URL does not use https: " + url); } logger.fine("Sending POST to " + url); logger.finest("POST body: " + body); byte[] bytes = body.getBytes(); HttpURLConnection conn = getConnection(url); conn.setDoOutput(true); conn.setUseCaches(false); conn.setFixedLengthStreamingMode(bytes.length); conn.setRequestMethod("POST"); conn.setRequestProperty("Content-Type", contentType); conn.setRequestProperty("Authorization", "key=" + key); OutputStream out = conn.getOutputStream(); try { out.write(bytes); } finally { close(out); } return conn; } /** * Creates a map with just one key-value pair. */ protected static final Map<String, String> newKeyValues(String key, String value) { Map<String, String> keyValues = new HashMap<String, String>(1); keyValues.put(nonNull(key), nonNull(value)); return keyValues; } /** * Creates a {@link StringBuilder} to be used as the body of an HTTP POST. * * @param name initial parameter for the POST. * @param value initial value for that parameter. * @return StringBuilder to be used an HTTP POST body. */ protected static StringBuilder newBody(String name, String value) { return new StringBuilder(nonNull(name)).append('=').append(nonNull(value)); } /** * Adds a new parameter to the HTTP POST body. * * @param body HTTP POST body. * @param name parameter's name. * @param value parameter's value. */ protected static void addParameter(StringBuilder body, String name, String value) { nonNull(body).append('&').append(nonNull(name)).append('=').append(nonNull(value)); } /** * Gets an {@link HttpURLConnection} given an URL. */ protected HttpURLConnection getConnection(String url) throws IOException { HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection(); return conn; } /** * Convenience method to convert an InputStream to a String. * <p> * If the stream ends in a newline character, it will be stripped. * <p> * If the stream is {@literal null}, returns an empty string. */ protected static String getString(InputStream stream) throws IOException { if (stream == null) { return ""; } BufferedReader reader = new BufferedReader(new InputStreamReader(stream)); StringBuilder content = new StringBuilder(); String newLine; do { newLine = reader.readLine(); if (newLine != null) { content.append(newLine).append('\n'); } } while (newLine != null); if (content.length() > 0) { // strip last newline content.setLength(content.length() - 1); } return content.toString(); } private static String getAndClose(InputStream stream) throws IOException { try { return getString(stream); } finally { if (stream != null) { close(stream); } } } static <T> T nonNull(T argument) { if (argument == null) { throw new IllegalArgumentException("argument cannot be null"); } return argument; } void sleep(long millis) { try { Thread.sleep(millis); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } }