public void read() {
    //必須是NioEventLoop方法調(diào)用的, 不能通過外部線程調(diào)用
    assert eventLoop().inEventLoop();
    //服務(wù)端channel的config
    final ChannelConfig config = config();
    //服務(wù)端channel的pipeline
    final ChannelPipeline pipeline = pipeline();
    //處理服務(wù)端接入的速率
    final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
    //設(shè)置配置
    allocHandle.reset(config);
    boolean closed = false;
    Throwable exception = null;
    try {
        try {
            do {
                //創(chuàng)建jdk底層的channel
                //readBuf用于臨時(shí)承載讀到鏈接
                int localRead = doReadMessages(readBuf);
                if (localRead == 0) {
                    break;
                }
                if (localRead < 0) {
                    closed = true;
                    break;
                }
                //分配器將讀到的鏈接進(jìn)行計(jì)數(shù)
                allocHandle.incMessagesRead(localRead);
                //連接數(shù)是否超過最大值
            } while (allocHandle.continueReading());
        } catch (Throwable t) {
            exception = t;
        }
        int size = readBuf.size();
        //遍歷每一條客戶端連接
        for (int i = 0; i < size; i ++) {
            readPending = false;
            //傳遞事件, 將創(chuàng)建NioSokectChannel進(jìn)行傳遞
            //最終會調(diào)用ServerBootstrap的內(nèi)部類ServerBootstrapAcceptor的channelRead()方法
            pipeline.fireChannelRead(readBuf.get(i));
        }
        readBuf.clear();
        allocHandle.readComplete();
        pipeline.fireChannelReadComplete();
        //代碼省略
    } finally {
        //代碼省略
    }
}

public void channelRead(ChannelHandlerContext ctx, Object msg) {
    final Channel child = (Channel) msg;
    //代碼省略
    try {
        //work線程注冊channel
        childGroup.register(child).addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                if (!future.isSuccess()) {
                    forceClose(child, future.cause());
                }
            }
        });
    } catch (Throwable t) {
        forceClose(child, t);
    }
}

public ChannelFuture register(final ChannelPromise promise) {
    ObjectUtil.checkNotNull(promise, "promise");
    promise.channel().unsafe().register(this, promise);
    return promise;
}

public final void register(EventLoop eventLoop, final ChannelPromise promise) {
    //省略驗(yàn)證代碼
    //所有的復(fù)制操作, 都交給eventLoop處理
    AbstractChannel.this.eventLoop = eventLoop;

    if (eventLoop.inEventLoop()) {
        //做實(shí)際主注冊
        register0(promise);
    } else {
        try {
            eventLoop.execute(new Runnable() {
                @Override
                public void run() {
                    register0(promise);
                }
            });
        } catch (Throwable t) {
            //代碼省略
        }
    }
}

private void register0(ChannelPromise promise) {
    try {
        //省略代碼
        //做實(shí)際的注冊
        doRegister();
        neverRegistered = false;
        registered = true;
        //觸發(fā)事件
        pipeline.invokeHandlerAddedIfNeeded();
        safeSetSuccess(promise);
        //觸發(fā)注冊成功事件
        pipeline.fireChannelRegistered();
        if (isActive()) {
            if (firstRegistration) {
                //傳播active事件(4)
                pipeline.fireChannelActive();
            } else if (config().isAutoRead()) {
                beginRead();
            }
        }
    } catch (Throwable t) {
        //省略代碼
    }
}

protected void doRegister() throws Exception {
    boolean selected = false;
    for (;;) {
        try {
            //jdk底層的注冊方法
            //第一個(gè)參數(shù)為selector, 第二個(gè)參數(shù)表示不關(guān)心任何事件
            selectionKey = javaChannel().register(eventLoop().selector, 0, this);
            return;
        } catch (CancelledKeyException e) {
            //省略代碼
        }
    }
}