io.netty.channel.nio.AbstractNioChannel
protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) { super(parent); this.ch = ch; this.readInterestOp = readInterestOp; ch.configureBlocking(false); }this.readInterestOp = readInterestOp把感兴趣的操作赋值给readInterestOp，上面传过来的是SelectionKey.OP_ACCEPT。
ch.configureBlocking(false)把刚才创建出来的channel设置为非阻塞。继续往父类追。
io.netty.channel.AbstractChannel
protected AbstractChannel(Channel parent) { this.parent = parent; id = newId(); unsafe = newUnsafe(); pipeline = newChannelPipeline(); } protected DefaultChannelPipeline newChannelPipeline() { return new DefaultChannelPipeline(this); }这里看到创建了ChannelPipeline，并关联到Channel上。再往下走一步。
io.netty.channel.DefaultChannelPipeline
protected DefaultChannelPipeline(Channel channel) { this.channel = ObjectUtil.checkNotNull(channel, "channel"); succeededFuture = new SucceededChannelFuture(channel, null); voidPromise = new VoidChannelPromise(channel, true); tail = new TailContext(this); head = new HeadContext(this); head.next = tail; tail.prev = head; }此时ChannelPipeline大致如下：
head --> tail 初始化ServerSocketChannel回到上面提到的重要的第2步： init(channel); 注意，实现类为ServerBootstrap，因为是Server端嘛。
io.netty.bootstrap.ServerBootstrap
@Override void init(Channel channel) { ChannelPipeline p = channel.pipeline(); final EventLoopGroup currentChildGroup = childGroup; final ChannelHandler currentChildHandler = childHandler; p.addLast(new ChannelInitializer<Channel>() { @Override public void initChannel(final Channel ch) { final ChannelPipeline pipeline = ch.pipeline(); ChannelHandler handler = config.handler(); if (handler != null) { pipeline.addLast(handler); } ch.eventLoop().execute(new Runnable() { @Override public void run() { pipeline.addLast(new ServerBootstrapAcceptor( ch, currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs)); } }); } }); }在ChannelPipeline加了一个ChannelHandler。此时ChannelPipeline大致如下：
head --> ChannelInitializer --> tail一旦serverSocketChannel注册到EventLoop(或者说Selector)上，便会触发这里initChannel的调用。避免绕晕了，这里暂时不去探究具体的调用逻辑。后面调用到这里的时候，再回过头来仔细探究。
ServerSocketChannel注册到Selector上回到上面提到的重要的第3步：config().group().register(channel);
通过分析类的继承层次(或者debug也行)可以跟踪调用到SingleThreadEventLoop的register方法。
io.netty.channel.SingleThreadEventLoop
@Override public ChannelFuture register(Channel channel) { return register(new DefaultChannelPromise(channel, this)); } @Override public ChannelFuture register(final ChannelPromise promise) { ObjectUtil.checkNotNull(promise, "promise"); promise.channel().unsafe().register(this, promise); return promise; }再往下跟，最终调用的是AbstractChannel的register方法，如下：
io.netty.channel.AbstractChannel
@Override public final void register(EventLoop eventLoop, final ChannelPromise promise) { AbstractChannel.this.eventLoop = eventLoop; eventLoop.execute(new Runnable() { @Override public void run() { register0(promise); } }); }往下跟eventLoop.execute()
io.netty.util.concurrent.SingleThreadEventExecutor
private void execute(Runnable task, boolean immediate) { addTask(task); startThread(); }addTask(task)把上面的Runnable放入到上面提到的Queue<Runnable> taskQueue，过程见如下代码：
io.netty.util.concurrent.SingleThreadEventExecutor
/** * Add a task to the task queue, or throws a {@link RejectedExecutionException} if this instance was shutdown * before. */ protected void addTask(Runnable task) { ObjectUtil.checkNotNull(task, "task"); if (!offerTask(task)) { reject(task); } } final boolean offerTask(Runnable task) { if (isShutdown()) { reject(); } return taskQueue.offer(task); }把task放入taskQueue后，就到startThread()这行代码了，进去瞧瞧。
io.netty.util.concurrent.SingleThreadEventExecutor
private void startThread() { doStartThread(); } private void doStartThread() { executor.execute(new Runnable() { @Override public void run() { SingleThreadEventExecutor.this.run(); } }); }继续追executor.execute，到这里才真正创建新的线程执行SingleThreadEventExecutor.this.run(), thread名称大致为nioEventLoopGroup-2-1，见如下代码：
io.netty.util.concurrent.ThreadPerTaskExecutor
@Override public void execute(Runnable command) { threadFactory.newThread(command).start(); }SingleThreadEventExecutor.this.run()实际执行的代码如下：