RESTlient Using Service- An Android Mobile Reads

In this blog I will show you how to call REST API through a service. First question come to your mind that Why Service one use AsyncTask to call REST. Well, you can do that if you want to frustrate your user by calling same request again and again.

Basically the role of service is to continuously run in background without worrying about application process, or user interaction with application.

RESTService is made to implement as a subclass of services, while the services are meant to encapsulate longer running operations in an android app, they are not inherently threaded. This is something that often confuses new android developers. So we will create a new thread whenever new API request is fired. Here is the details of the code snippet

public class  RestClient extends Service{

private static final String TAG = RestClient.class.getName();
private final ServiceBinder mBinder = new ServiceBinder();
private Looper mServiceLooper;
private ServiceHandler mServiceHandler;

@Override     public void onCreate() {

super.onCreate();

HandlerThread thread = new HandlerThread("RestClient[" + "SoPoint" + "]");
thread.start();

mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}

@Override     public int onStartCommand(Intent intent, int flags, int startId)
{
return START_STICKY;
}

@Override     public IBinder onBind(Intent intent)
{

return mBinder;
}

@Override     public boolean onUnbind(Intent intent)
{         return super.onUnbind(intent);
}

@Override     public void onDestroy()
{         mServiceLooper.quit();
}

private void processRequest(Intent intent)
{

Message msg =  mServiceHandler.obtainMessage();
msg.obj = intent;         mServiceHandler.sendMessage(msg);
}

private void doWork(Intent intent){

Uri    serviceURL = intent.getData();
Bundle extras = intent.getExtras();
int action  = intent.getIntExtra(ServiceHelper.Constants.EXTRA_REQUEST,
ServiceHelper.Constants.GET);
Bundle    params   = extras.getParcelable(ServiceHelper.Constants.EXTRA_PARAMS);

// Here we define our base request object which we will
// send to our REST service via HttpClient.

HttpRequestBase request = null;
request = new HttpGet();
attachUriWithQuery(request, serviceURL, params);
if (request != null) {
HttpClient client = new DefaultHttpClient();
try{

// Finally, we send our request using HTTP. This is the synchronous
// long operation that we need to run on this thread.

ResponseHandler<String> res = new BasicResponseHandler();
String response = client.execute(request,res);
Log.v(TAG,"Response---"+response);

/*After getting response from server either we can pass the name of class used for parsing the response and instantiate using reflection or regiater a reciever in our activity*/

}
catch (Exception e){

e.printStackTrace();
}
}

}

class ServiceBinder extends Binder
{

public ServiceBinder(){
}

public void processRequest(Intent intent)
{

RestClient.this.processRequest(intent);
}
}

private class ServiceHandler extends Handler
{
public ServiceHandler(Looper looper)
{

super(looper);

}

@Override   public void handleMessage(Message msg)
{

doWork((Intent)msg.obj);
}
}

In the code shown above we have created a handler thread and using that for creating new thread for every request.

Message msg =  mServiceHandler.obtainMessage();
msg.obj = intent;
mServiceHandler.sendMessage(msg);

And one more point to note how request is made using intent. We are passing Action Verb(GET,POST,PUT,DELETE) , and Service URL as URI. Once we get a response from server we could either deliver that response to Broadcast Receiver or we can directly pass the name of the class that is used for parsing that response in intent and get an object of that class using reflection.

If you find any bugs or have any questions, let me know in the comments, We will love to address them.

Happy coding…

Written By: Prateek Aggarwal, Android Mobile Developer, Mindfire Solutions

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