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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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