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 no.ntnu.wifimanager; import static no.ntnu.wifimanager.CommonUtilities.HTTP_CONTENT_TYPE_URL_ENCODED; import static no.ntnu.wifimanager.CommonUtilities.LOG_TAG; import static no.ntnu.wifimanager.CommonUtilities.URL_REGISTER_APP_FOR_GCM; import static no.ntnu.wifimanager.CommonUtilities.URL_SERVER; import static no.ntnu.wifimanager.CommonUtilities.displayMessage; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.UnsupportedEncodingException; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Random; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.NameValuePair; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.message.BasicHeader; import org.apache.http.message.BasicNameValuePair; import org.apache.http.protocol.HTTP; import org.json.JSONArray; import org.json.JSONException; import android.content.Context; import android.content.SharedPreferences; import android.preference.PreferenceManager; import android.util.Log; import com.google.android.gcm.GCMRegistrar; /** * 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(); public static final String EXTRA_CLIENT_NAME = "no.ntnu.wifimanager.CLIENT_NAME"; public static final String EXTRA_CLIENT_MAC = "no.ntnu.wifimanager.CLIENT_MAC"; /** * Register this account/device pair within the server. * * @return whether the registration succeeded or not. */ public static boolean register(final Context context, final String regId) { Log.i(LOG_TAG, "registering device (regId = " + regId + ")"); SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context); String userId = preferences.getString("email", "NA"); Map<String, String> params = new HashMap<String, String>(); params.put("regId", regId); params.put("userId", userId); 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(LOG_TAG, "Attempt #" + i + " to register"); try { displayMessage(context, context.getString(R.string.server_registering, i, MAX_ATTEMPTS)); HTTPpost(URL_REGISTER_APP_FOR_GCM, params, HTTP_CONTENT_TYPE_URL_ENCODED); 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(LOG_TAG, "Failed to register on attempt " + i, e); if (i == MAX_ATTEMPTS) { break; } try { Log.d(LOG_TAG, "Sleeping for " + backoff + " ms before retry"); Thread.sleep(backoff); } catch (InterruptedException e1) { // Activity finished before we complete - exit. Log.d(LOG_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. */ public static void unregister(final Context context, final String regId) { Log.i(LOG_TAG, "unregistering device (regId = " + regId + ")"); String serverUrl = URL_SERVER + "/unregister"; Map<String, String> params = new HashMap<String, String>(); params.put("regId", regId); try { HTTPpost(serverUrl, params, HTTP_CONTENT_TYPE_URL_ENCODED); 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 server. * * @param serverUrl POST address. * @param params request parameters. * * @throws IOException propagated from POST. */ public static void HTTPpost(String serverUrl, Map<String, String> params, String contentType) throws IOException { URL url; try { url = new URL(serverUrl); } catch (MalformedURLException e) { throw new IllegalArgumentException("invalid url: " + serverUrl); } StringBuilder bodyBuilder = new StringBuilder(); Iterator<Entry<String, String>> iterator = params.entrySet().iterator(); // constructs the POST body using the parameters while (iterator.hasNext()) { Entry<String, String> param = iterator.next(); bodyBuilder.append(param.getKey()).append('=').append(param.getValue()); if (iterator.hasNext()) { bodyBuilder.append('&'); } } String body = bodyBuilder.toString(); Log.v(LOG_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", contentType); // 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(); } } } public static JSONArray getJSONArray(String url, String userId) { InputStream is = null; JSONArray jArray = null; String json = ""; // Making HTTP request try { // defaultHttpClient DefaultHttpClient httpClient = new DefaultHttpClient(); HttpPost httpPost = new HttpPost(url); List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1); nameValuePairs.add(new BasicNameValuePair("user_id", userId)); httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); HttpResponse httpResponse = httpClient.execute(httpPost); HttpEntity httpEntity = httpResponse.getEntity(); is = httpEntity.getContent(); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } try { BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + "\n"); } is.close(); json = sb.toString(); } catch (Exception e) { Log.e("Buffer Error", "Error converting result " + e.toString()); } // try parse the string to a JSON object try { jArray = new JSONArray(json); } catch (JSONException e) { Log.e("JSON Parser", "Error parsing data " + e.toString()); } // return JSON String return jArray; } public static void postJSON(String url, String JSONString) { HttpPost httpPost = new HttpPost(url); StringEntity se; try { se = new StringEntity(JSONString); se.setContentType("application/json"); se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json")); //httpPost.setHeader("Accept", "application/json"); httpPost.setEntity(se); HttpResponse resp = new DefaultHttpClient().execute(httpPost); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClientProtocolException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }