支持分布式的callback

项目背景：

       之前在某次培训的分享中，谈到rxjava、vertx等开源框架，也了解到callback概念，在分享的中某位童鞋谈到分布式下callback如何处理，说实话在当时的环境能够通过几句话描述callback都比较困难，更何况描述分布式下的callback，所以本文我想通过基于jgroup的方式，更好阐述我的理解如何处理分布式下的callback。

public class ReplyingCallback implements CommandCallback<Object, Object> {

    private final JChannel channel;
    private final Serializer serializer;

    private static final Logger logger = LoggerFactory.getLogger(ReplyingCallback.class);
    private final Address address;

    public ReplyingCallback(JChannel channel, Address address, Serializer serializer) {
        this.address = address;
        this.channel = channel;
        this.serializer = serializer;
    }

    @Override
    public void onSend(CommandMessage<?> commandMessage, Object result) {
        try {
            channel.send(address, new ReplyMessage(commandMessage.getIdentifier(),
                                                   result,
                                                   null, serializer));
        } catch (Exception e) {
            logger.error("Unable to send reply to command [name: {}, id: {}]. ",
                         commandMessage.getCommandName(), commandMessage.getIdentifier(), e);
            throw new CommandResponseProcessingFailedException(String.format(
                    "An error occurred while attempting to process command response of type : %s, Exception Message: %s",
                    result.getClass().getName(), e.getMessage()), e);
        }
    }