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Re: [ecf-dev] Issue adding custom serialization to ecf provider 
Hi Peter,

On 4/28/2017 5:06 AM, Peter Hermsdorf wrote:

hi all,
i'm currently trying to implement custom serialization for the ecf generic remote service provider using the kryo library. A problem occurs with deserializing instances of org.eclipse.ecf.remoteservice.RemoteServiceRegistrationImpl.Properties. Thats an inner class derived from java.util.Hastable. There occurs a NullPointer Exception when Kryo tries to add Elements to this Map (Hastable.class around Line 465).
The Reason: the field table of Hashtable does not get initialized. Initialization is done in the constructor. But because the derived Properties class hides the no-arg constructor of hastable the deserialization framework creates an instance of the class Properties "magically", but of course without calling the no-op Constructor of hastable. So the member table is null and leads to that problem.
Hmm. Would adding a no-arg constructor to RemoteServiceRegistrationImpl.Properties help? That could be done pretty easily, but I'm not sure if that will work with Kryo's deserialization behavior. 

i.e. something like:

protected Properties() {
    super();
}
Of course this is in the first step a problem with the non-java-default serialization,
I thought it was required/expected that the superclass null/empty constructor would always be called if subclass null constructor is called (serialization or otherwise). Otherwise, I don't think superclasses can ever guarantee proper initialization. 



but it's an more or less obvious issue for a DTO Object...
Has anyone experienced this problem or has any ideas on how to workaround this? 

Any ideas, comments or suggestions are more than welcome!

My Setup:
I registered custom IHostContainerSelector and IConsumerContainerSelector where i'm registering a custom serializer ~like this: 

    @Override
protected IRemoteServiceContainer createContainer(final ContainerTypeDescription containerTypeDescription, final String containerTypeDescriptionName, @SuppressWarnings("rawtypes") final Map properties) 
            throws SelectContainerException {
final IRemoteServiceContainer serviceContainer = super.createContainer(containerTypeDescription, 
                containerTypeDescriptionName, properties);
final ISharedObjectContainer container = (ISharedObjectContainer) serviceContainer.getContainer(); container.setSharedObjectMessageSerializer(new KryoSharedMessageSerializer()); 
...

The MessageSerializer:
public class KryoSharedMessageSerializer implements ISharedObjectMessageSerializer { 

    Kryo kryo = new Kryo();
    final ByteArrayOutputStream baos = new ByteArrayOutputStream();

    public KryoSharedMessageSerializer() {
kryo.setInstantiatorStrategy(new Kryo.DefaultInstantiatorStrategy(new StdInstantiatorStrategy())); 
        kryo.setClassLoader(this.getClass().getClassLoader());
    }

    @Override
public byte[] serializeMessage(final ID sharedObjectID, final Object message) throws IOException { 
        baos.reset();
        final Output output = new Output(baos);
        kryo.writeClassAndObject(output, message);
        output.close();
        return baos.toByteArray();
    }

    @Override
public Object deserializeMessage(final byte[] data) throws IOException, ClassNotFoundException { 
        return kryo.readClassAndObject(new Input(data));
    }
}

Thanks, bye Peter


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