Java tutorial
/* * Copyright (c) 2013 Nimbits 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 expressed or implied. See the License for the specific language governing permissions and limitations under the License. */ package com.nimbits.server.gcm; import org.json.simple.JSONObject; import org.json.simple.JSONValue; import org.json.simple.parser.JSONParser; import java.io.*; import java.net.HttpURLConnection; import java.net.URL; import java.net.URLEncoder; import java.util.*; import java.util.Map.Entry; import java.util.logging.Level; import java.util.logging.Logger; import static com.nimbits.server.gcm.Constants.*; /** * 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 java.io.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)) { Result.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 java.io.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, java.util.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 java.io.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 (Exception 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 java.io.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 java.net.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(); } } }