Android: Object is not received properly using ObjectOutputstream & ObjectInputstream

Question

Situation : A client sends an object over to the server using ObjectOutputStream. I flush() and reset() after sending.

The server receives and object, does some processing and sends it back to the client. Immediately after sending, I call ObjectOutputStream.reset(). Prior to sending, I also print a field in this object in the console.

The client receives the same object back from the server using ObjectInputStream().

Problem : After receiving the object back at the client, the field that printed fine at the Server's console now prints NULL.

What I've tried :I use flush() and reset() after sending and receiving at both ends.

Why is the received object corrupted ?

Client code -- run() of Thread:

                objectOutputStream.flush();
                    objectOutputStream.reset();

                    //out.println("#SerialO#");
                    objectOutputStream.writeBoolean(true);


                    if(((Dodger) this.obj).getRemotable()){

                            Log.i("ENDPOINT", "Sending Serialized ObjecInstance ...");
                            objectOutputStream.writeObject(this.obj);
                            objectOutputStream.flush();
                            objectOutputStream.reset();
                    }

Client code -- Function called TO receive Server's O/P

        objectOutputStream.writeBoolean(false);

        objectOutputStream.flush();
        objectOutputStream.reset();
        objectOutputStream.writeObject(args);

        objectOutputStream.flush();
        objectOutputStream.reset();

        res = objectInputStream.readObject();

        ......
        else if (res instanceof Dodger)
        {
            res = (Dodger) res;
            res3 = (Dodger)res;
            Log.v("CLIENT", "Object received Dodger "+ctr);
        }
        else
            if(res==null)
                Log.v("CLIENT", "Object received is NULL "+ctr);
            else
                Log.v("CLIENT", "Object received of UNKNOWN Type  "+ctr);

catch (Exception e)
        {
            Log.e("CLIENT receive error 3",e.toString());
        }

                    // ** ERROR COMES AT THIS LINE. NULL VALUE IS PRINTED **
            System.out.println("ENDPOINT GETPOSITION  -> "+res3.getPosition());

Server code - main thread.

flg = mInput.readBoolean();//this.input.readLine().toString();

                    System.out.println("SERVER Received flg as "+flg);

                    if(flg){

                        Log.d("SERVER","Received an object");
                        sendObj  = mInput.readObject();
                        //mOutput.flush();
                        CommunicationThread commThread = new CommunicationThread(this.clientSocket,it,sendObj);
                        new Thread(commThread).start();
                    }
                    else //if(flg.equalsIgnoreCase("P"))
                    {
                        Object[] recArgs  = (Object[])mInput.readObject();

                        executor = Executors.newFixedThreadPool(1);
                        executor.submit(new updateUIThread(this.clientSocket, this.msg, recArgs));

                        //Temp
                        //executor.execute(new updateUIThread(this.clientSocket, this.msg, recArgs));
                        //break;
                    }

Server code - Communication Thread:

            if (mInput==null){
                Log.i("SERVER","Receiving very first serialized obj");
                 mOutput = new ObjectOutputStream(this.clientSocket.getOutputStream());
                System.out.println("Inside Server's Comm Thread 2 ");
                mInput = new ObjectInputStream(new BufferedInputStream(this.clientSocket.getInputStream()));
            }
            {

                System.out.println("Inside Server's Comm Thread 3 ");

                if (obj instanceof Dodger) {
                    obj1 = (Dodger)obj;
                    //...

                    System.out.println("Dodger Object Type:  " + obj.getClass().getName());

                }
                else {
                    System.out.println("Unexpected object type:  " + obj.getClass().getName());
                }

Server code - updateUIThread:

    obj1.setPosition((Vec2)this.recArgs[0]);

// BELOW IT PRINTS THE PROPER VALUE, BEFORE SENDING BACK TO CLIENT
    System.out.println("SERVER  GETPOSITION "+obj1.getPosition());

            mOutput.reset();
            mOutput.writeObject(obj1);
            mOutput.reset();

Answer 1

Solved it. Turns out that the variable being returned from getPosition() was from a Super Class that did NOT implement Serializable. That's why even though the object returned correctly, that particular variable inside the object was "lost in transit".

Moral of the story: Whenever you make a class Serializable, all its Super Classes must also implement Serializable !!