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.app; import static com.google.android.gcm.demo.app.CommonUtilities.SERVER_URL; import static com.google.android.gcm.demo.app.CommonUtilities.TAG; import static com.google.android.gcm.demo.app.CommonUtilities.displayMessage; import com.google.android.gcm.GCMRegistrar; import android.content.Context; import android.util.Log; import java.io.IOException; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; import java.util.Random; import org.json.JSONObject; /** * Helper class used to communicate with the demo server. */ public final class ServerUtilities { private static final int MAX_ATTEMPTS = 5; private static final int BACKOFF_MILLI_SECONDS = 2000; private static final Random random = new Random(); /** * Register this account/device pair within the server. * * @return whether the registration succeeded or not. */ static boolean register(final Context context, final String regId) { Log.i(TAG, "registering device (regId = " + regId + ")"); String serverUrl = SERVER_URL; Map<String, String> params = new HashMap<String, String>(); params.put("regId", regId); long backoff = BACKOFF_MILLI_SECONDS + random.nextInt(1000); // Once GCM returns a registration id, we need to register it in the // demo server. As the server might be down, we will retry it a couple // times. for (int i = 1; i <= MAX_ATTEMPTS; i++) { Log.d(TAG, "Attempt #" + i + " to register"); try { displayMessage(context, context.getString(R.string.server_registering, i, MAX_ATTEMPTS)); post(serverUrl, params); GCMRegistrar.setRegisteredOnServer(context, true); String message = context.getString(R.string.server_registered); CommonUtilities.displayMessage(context, message); return true; } catch (IOException e) { // Here we are simplifying and retrying on any error; in a real // application, it should retry only on unrecoverable errors // (like HTTP error code 503). Log.e(TAG, "Failed to register on attempt " + i, e); if (i == MAX_ATTEMPTS) { break; } try { Log.d(TAG, "Sleeping for " + backoff + " ms before retry"); Thread.sleep(backoff); } catch (InterruptedException e1) { // Activity finished before we complete - exit. Log.d(TAG, "Thread interrupted: abort remaining retries!"); Thread.currentThread().interrupt(); return false; } // increase backoff exponentially backoff *= 2; } } String message = context.getString(R.string.server_register_error, MAX_ATTEMPTS); CommonUtilities.displayMessage(context, message); return false; } /** * Unregister this account/device pair within the server. */ static void unregister(final Context context, final String regId) { Log.i(TAG, "unregistering device (regId = " + regId + ")"); String serverUrl = SERVER_URL + "/unregister"; Map<String, String> params = new HashMap<String, String>(); params.put("regId", regId); try { post(serverUrl, params); GCMRegistrar.setRegisteredOnServer(context, false); String message = context.getString(R.string.server_unregistered); CommonUtilities.displayMessage(context, message); } catch (IOException e) { // At this point the device is unregistered from GCM, but still // registered in the server. // We could try to unregister again, but it is not necessary: // if the server tries to send a message to the device, it will get // a "NotRegistered" error message and should unregister the device. String message = context.getString(R.string.server_unregister_error, e.getMessage()); CommonUtilities.displayMessage(context, message); } } /** * Issue a POST request to the server. * * @param endpoint POST address. * @param params request parameters. * * @throws IOException propagated from POST. */ private static void post(String endpoint, Map<String, String> params) throws IOException { URL url; try { url = new URL(endpoint); } catch (MalformedURLException e) { throw new IllegalArgumentException("invalid url: " + endpoint); } JSONObject jsonObj = new JSONObject(params); String body = jsonObj.toString(); Log.v(TAG, "Posting '" + body + "' to " + url); byte[] bytes = body.getBytes(); HttpURLConnection conn = null; try { conn = (HttpURLConnection) url.openConnection(); conn.setDoOutput(true); conn.setUseCaches(false); conn.setFixedLengthStreamingMode(bytes.length); conn.setRequestMethod("POST"); conn.setRequestProperty("Content-Type", "application/json"); // post the request OutputStream out = conn.getOutputStream(); out.write(bytes); out.close(); // handle the response int status = conn.getResponseCode(); if (status != 200) { throw new IOException("Post failed with error code " + status); } } finally { if (conn != null) { conn.disconnect(); } } } }