Push notifications with Parse.com

Parse.com provides a set of handy tools to rapidly build mobile applications that needs back-end. One of the main provided features is the push notifications that enables asynchronous and real-time communiation. This post illustrates how to set up the push mechnism in an Android application.

• First, we need to create an Account at Parse.com and register an application to have an application key and client key
• Second, in the application settings wen have to enable push notifications
• Then, download the latestes Parse SDK, i.e. the parse.jar
• Finally, code time

In the manifest, we need to add the following lines to ask permessions

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" /> 
<uses-permission android:name="android.permission.VIBRATE" />

Then, before the </application> register a broadcast receiver

<receiver android:name=".PushReceiver">
   <intent-filter>  
 <action android:name="com.telethonix.NOTIFICATION"> </action>
   </intent-filter>
</receiver>

Then create the PushReceiver class as follow:

public class PushReceiver extends BroadcastReceiver {
   public final static String TAG = PushReceiver.class.getSimpleName(); 
   @Override
   public void onReceive(Context context, Intent intent) {     
      try {
 Bundle extras = intent.getExtras();        
 String message = extras != null ? extras.getString("com.parse.Data") : "";    
 Log.i(TAG, "Received message: "+message);
       // do something with the received data
      } catch (JSONException e) {
 e.printStackTrace();
      }  
   }
}

Finnaly in the main activity, we should initiate parse with the application keys, and send a notification

String app_id     = "your application key";
String client_key = "your client key";
Parse.initialize(this, app_id, client_key);
// subscribe to be notified
PushService.subscribe(MainActivity.this, "channel", MainActivity.class);
// push a message
ParsePush push = new ParsePush(); push.setChannel("channel");
push.setData(data);
push.sendInBackground(new SendCallback(){   
   @Override
   public void done(ParseException arg0){
      Log.i(TAG, "push sent done!");
   }
});

More details at Push Developer Guide.

J2EE Solution Logs

Changing the context root of a dynamic web app URL (StackOverflow)

1. Right click on the project in the project explorer tab, the choose properties.
2. Set the new context root in the Web Project Settings.

Exception when launching jetty (StackOverflow)
java.lang.NoClassDefFoundError: org/objectweb/asm/ClassVisitor
It seems that jetty cannot find the asm.jar file in its classpath, check this as follow:

1. On eclipse, go to the Servers view (or open it via window -> view -> Servers)
2. Right click on jetty, then choose Open or just type F3
3. On the Overview tab, click on Open Lauchn Configuration
4. Go to Classpath tab and check for asm.jar

If you cannot find it, then you should manually download it from the project website.

Register a listener to do things before the VM exits (even if you "Ctrl-C" the running example before it's completed)

private void registerShutdownHook() {
   Runtime.getRuntime().addShutdownHook( new Thread() {
      @Override
      public void run() {
         // do some thing
      }
   });
}

Increase Maven memory, in mvn.bat add:
set MAVEN_OPTS=-Xmx2048m -XX:MaxPermSize=512m

To be continued