NettyClient和Channel

    @Override
    protected void doConnect() throws Throwable {
        long start = System.currentTimeMillis();
        ChannelFuture future = bootstrap.connect(getConnectAddress());
        boolean ret = future.awaitUninterruptibly(3000, TimeUnit.MILLISECONDS);
            if (ret && future.isSuccess()) {
                Channel newChannel = future.channel();
              NettyClient.this.channel = newChannel;
           }
    }

NettyClient在调用connect方法时,会将io.netty.channel.Channel关联起来,
有了io.netty.channel.Channel,NettyClient才具备了真正的收发数据的能力

NettyChannel是Channel的实现,是对io.netty.channel.Channel的封装,NettyChannel以io.netty.channel.Channel为key,将其转换为NettyChannel,对外提供封装调用方法

final class NettyChannel extends AbstractChannel {

    private static final Logger logger = LoggerFactory.getLogger(NettyChannel.class);

    private static final ConcurrentMap<Channel, NettyChannel> channelMap = new ConcurrentHashMap<Channel, NettyChannel>();

    private final Channel channel;

    private final Map<String, Object> attributes = new ConcurrentHashMap<String, Object>();

    private NettyChannel(Channel channel, URL url, ChannelHandler handler) {
        super(url, handler);
        if (channel == null) {
            throw new IllegalArgumentException("netty channel == null;");
        }
        this.channel = channel;
    }

    static NettyChannel getOrAddChannel(Channel ch, URL url, ChannelHandler handler) {
        if (ch == null) {
            return null;
        }
        NettyChannel ret = channelMap.get(ch);
        if (ret == null) {
            NettyChannel nettyChannel = new NettyChannel(ch, url, handler);
            if (ch.isActive()) {
                ret = channelMap.putIfAbsent(ch, nettyChannel);
            }
            if (ret == null) {
                ret = nettyChannel;
            }
        }
        return ret;
    }

    @Override
    public void send(Object message, boolean sent) throws RemotingException {
        super.send(message, sent);

        boolean success = true;
        int timeout = 0;
        try {
            ChannelFuture future = channel.writeAndFlush(message);
            if (sent) {
                timeout = getUrl().getPositiveParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT);
                success = future.await(timeout);
            }
        } catch (Throwable e) {
        }
    }
}

NettyClient的send方法调用

其内部真正调用的为Channel的send方法

    public void send(Object message, boolean sent) throws RemotingException {
        if (send_reconnect && !isConnected()) {
            connect();
        }
        Channel channel = getChannel();
        //TODO Can the value returned by getChannel() be null? need improvement.
        if (channel == null || !channel.isConnected()) {
            throw new RemotingException(this, "message can not send, because channel is closed . url:" + getUrl());
        }
        channel.send(message, sent);
    }