Netty客户端接入流程NioSocketChannel创建解析

public void read() {
    //必须是NioEventLoop方法调用的, 不能通过外部线程调用
    assert eventLoop().inEventLoop();
    //服务端channel的config
    final ChannelConfig config = config();
    //服务端channel的pipeline
    final ChannelPipeline pipeline = pipeline();
    //处理服务端接入的速率
    final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
    //设置配置
    allocHandle.reset(config);
    boolean closed = false;
    Throwable exception = null;
    try {
        try {
            do {
                //创建jdk底层的channel
                //readBuf用于临时承载读到链接
                int localRead = doReadMessages(readBuf);
                if (localRead == 0) {
                    break;
                }
                if (localRead < 0) {
                    closed = true;
                    break;
                }
                //分配器将读到的链接进行计数
                allocHandle.incMessagesRead(localRead);
                //连接数是否超过最大值
            } while (allocHandle.continueReading());
        } catch (Throwable t) {
            exception = t;
        }
        int size = readBuf.size();
        //遍历每一条客户端连接
        for (int i = 0; i < size; i ++) {
            readPending = false;
            //传递事件, 将创建NioSokectChannel进行传递
            //最终会调用ServerBootstrap的内部类ServerBootstrapAcceptor的channelRead()方法
            pipeline.fireChannelRead(readBuf.get(i));
        }
        readBuf.clear();
        allocHandle.readComplete();
        pipeline.fireChannelReadComplete();
        //代码省略
    } finally {
        //代码省略
    }
}

private final List<Object> readBuf = new ArrayList<Object>();

protected int doReadMessages(List<Object> buf) throws Exception {
    //根据当前jdk底层的serverSocketChannel拿到jdk底层channel
    SocketChannel ch = javaChannel().accept();
    try {
        if (ch != null) {
            //封装成一个NioSokectChannel扔到buf中
            buf.add(new NioSocketChannel(this, ch));
            return 1;
        }
    } catch (Throwable t) {
        //代码省略
    }
    return 0;
}

public NioSocketChannel(Channel parent, SocketChannel socket) {
    super(parent, socket);
    config = new NioSocketChannelConfig(this, socket.socket());
}

protected AbstractNioByteChannel(Channel parent, SelectableChannel ch) { 
    super(parent, ch, SelectionKey.OP_READ);
}

protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
    super(parent);
    this.ch = ch;
    this.readInterestOp = readInterestOp;
    try {
        //设置为非阻塞
        ch.configureBlocking(false);
    } catch (IOException e) {
        //代码省略
    }
}

protected AbstractChannel(Channel parent) {
    this.parent = parent;
    id = newId();
    unsafe = newUnsafe();
    pipeline = newChannelPipeline();
}

protected AbstractNioUnsafe newUnsafe() {
    return new NioByteUnsafe();
}

public NioSocketChannel(Channel parent, SocketChannel socket) {
    super(parent, socket);
    config = new NioSocketChannelConfig(this, socket.socket());
}

private NioSocketChannelConfig(NioSocketChannel channel, Socket javaSocket) {
    super(channel, javaSocket);
}

public DefaultSocketChannelConfig(SocketChannel channel, Socket javaSocket) {
    super(channel);
    if (javaSocket == null) {
        throw new NullPointerException("javaSocket");
    }
    //保存当前javaSocket
    this.javaSocket = javaSocket;
    //是否禁止Nagle算法
    if (PlatformDependent.canEnableTcpNoDelayByDefault()) {
        try {
            setTcpNoDelay(true);
        } catch (Exception e) {
        }
    }
}

public DefaultChannelConfig(Channel channel) {
    this(channel, new AdaptiveRecvByteBufAllocator());
}