gistfile1.java

interface ManyNetworkHandlerFactory {
	Set<NetworkHandler> create(NetworkClient client);
}

class NetworkHandlersModule extends AbstractModule {
	protected void configure() {
		install(new ManyFactoryModuleBuilder(NetworkClient.class)
			.bind(AuthenticationHandler.class)
			.build());
	}
}

class LoginNettyService extends NettyService {
	@Inject ManyNetworkHandlerFactory factory;

	protected NetworkClient newClient(NetworkSession session) {
		DefaultLoginClient client = new DefaultLoginClient(this, session);
		client.setHandlers(factory.create(client));

		return client;
	}
}

class AuthenticationHandler implements NetworkHandler {
	final NetworkClient client;
	final Repository<User> users;

	@Inject AuthenticationHandler(NetworkClient client, Repository<User> users) {
		this.client = client;
		this.users = users;
	}

	protected void write(NetworkMessage msg) {
		client.getSession().write(msg);
	}

	@Handler
	public void handleIdentificationMessage(IdentificationMessage msg) {
		User user = users.findBy("name", msg.username);

		if (user == null) {
			write(new IdentificationFailureMessage(IdentificationFailureReason.BAD_CREDENTIALS));
		}

		// ...
	}
}