dubbo系列之网络通信-consumer的接收原理

简介

接着上一篇博客往下，在provider完成接收和发送之后，consumer才来接收，过程和provider的接收差不多，但还是有一点细微的区别，我们这篇博客就重点看看区别之处，相同的地方就直接跳过了，可参考上一篇博客。

源码介绍

NettyHandler类

messageReceived()

public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
    NettyChannel channel = NettyChannel.getOrAddChannel(ctx.getChannel(), url, handler);
    try {
        handler.received(channel, e.getMessage());
    } finally {
        NettyChannel.removeChannelIfDisconnected(ctx.getChannel());
    }
}

看一下此时的e.getMessage()的值

省略一段和provider相同的debug路程，直接进入重点

HeaderExchangeHandler类

handleResponse()

public void received(Channel channel, Object message) throws RemotingException {
 	if (message instanceof Request) {
                // handle request.
                Request request = (Request) message;
                if (request.isEvent()) {
                    handlerEvent(channel, request);
                } else {
                    if (request.isTwoWay()) {
                        Response response = handleRequest(exchangeChannel, request);
                        channel.send(response);
                    } else {
                        handler.received(exchangeChannel, request.getData());
                    }
                }
            } else if (message instanceof Response) {
                handleResponse(channel, (Response) message);
}

区别来了，provider的是Request，而我们从上面的e.getMessage值得图就能看出来，consumer是进入Response循环，接着往下看。

DefaultFuture类

doReceived()

//涉及到异步变同步的锁机制
private void doReceived(Response res) {
    lock.lock();//加锁
    try {
        response = res;//复制
        if (done != null) {
            done.signal();
        }
    } finally {
        lock.unlock();//解锁
    }
    if (callback != null) {
        invokeCallback(callback);
    }
}

一解锁，控制台立马打印

[14:05:26] Hello world0, response form provider: 10.1.86.250:20880

这样consumer就拿到了数据了。

涉及到异步转同步得问题下一篇博客再介绍。