How to serialize a third-party non-serializable final class (e.g. google's LatLng class)?

Question

I\'m using Google\'s LatLng class from the v2 Google Play Services. That particular class is final and doesn\'t implement java.io.Serializable. Is there any way

Answer 1

It's not Serializable but it is Parcelable, if that would be an option instead. If not you could handle the serialization yourself:

public class MyDummyClass implements java.io.Serialiazable {
    // mark it transient so defaultReadObject()/defaultWriteObject() ignore it
    private transient com.google.android.gms.maps.model.LatLng mLocation;

    // ...

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeDouble(mLocation.latitude);
        out.writeDouble(mLocation.longitude);
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        mLocation = new LatLng(in.readDouble(), in.readDouble());
    }
}

Answer 2

You can have a look at ObjectOutputStream .

First, you'll have to create a drop-in replacement for your object :

    public class SerializableLatLng implements Serializable {

    //use whatever you need from LatLng

    public SerializableLatLng(LatLng latLng) {
        //construct your object from base class
    }   

    //this is where the translation happens
    private Object readResolve() throws ObjectStreamException {
        return new LatLng(...);
    }

}

Then create an appropriate ObjectOutputSTream

public class SerializableLatLngOutputStream extends ObjectOutputStream {

    public SerializableLatLngOutputStream(OutputStream out) throws IOException {
        super(out);
        enableReplaceObject(true);
    }

    protected SerializableLatLngOutputStream() throws IOException, SecurityException {
        super();
        enableReplaceObject(true);
    }

    @Override
    protected Object replaceObject(Object obj) throws IOException {
        if (obj instanceof LatLng) {
            return new SerializableLatLng((LatLng) obj);
        } else return super.replaceObject(obj);
    }

}

Then you'll have to use these streams when serializing

private static byte[] serialize(Object o) throws Exception {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    ObjectOutputStream oos = new SerializableLatLngOutputStream(baos); 
    oos.writeObject(o);
    oos.flush();
    oos.close();
    return baos.toByteArray();
}