Trying to call specific service plugin

[mark.engel]

Hello,

I'm trying to build a service plugin system.

On the server side I have different implementations of an interface all labeled with the same @Service annotation.

@Service(Services.Plugin)

public class Plugin[1..n] {

  @Command(Command.Get)

  public void get(Message m) {

    MessageBuilder

      .createConversation(message)

      .toSubject(Receiver.Plugin)

      .with(Parts.Value, value)

      .defaultErrorHandling()

      .reply();

  }

  @Command(Command.Set)

  public void set(Message m) {

    ...

  }

@Service(Services.Plugin)

public class Plugin[1..n] {

  @Command(Command.Get)

  public void get(Message m) {

    MessageBuilder

      .createConversation(message)

      .toSubject(Receiver.Plugin)

      .with(Parts.Value, value)

      .defaultErrorHandling()

      .reply();

  }

  @Command(Command.Set)

  public void set(Message m) {

    ...

  }

On the client side I can call all getter methods with

MessageBuilder
  .createMessage()
  .toSubject(Service.Plugin)
  .command(Command.Get)
  .noErrorHandling()
  .sendNowWith(bus);

and I receive my updates on the subscription to Receiver.Plugin

Now I have the problem that I get Null Pointer Exceptions when I try to call the set method of one plugin.

I thought that I could call the set method of a specific plugin if I respond to the message I received from Plugin.get()

I tried to use the following function call from the client

        MessageBuilder

                .createConversation(messageReceivedFromServer)

                .toSubject(Service.Plugin) // .subjectProvided() did also not work

                .command(Command.Set)

                .with(Parts.Value, newValue)

                .defaultErrorHandling()

                .reply();

Is it only possible to use createConversation on the server side?

Is it possible to call one service of several if they have the same name?

Or am I doing some mistake here?

Here is the exception I receive when I try to send the latter method.

https://gist.github.com/d9f7855e0f3d70af2fe7