netty源码分析(一)-启动

对于netty的理解，首先要熟悉NIO相关的概念，可以参考学习这里：Java NIO

以NioServerSocket实现为例，netty的启动过程分析：

netty的启动入口，我们一般会这样配置：

    ChannelFactory serverChannelFacory = new NioServerSocketChannelFactory(Executors.newCachedThreadPool(),Executors.newCachedThreadPool());
    ServerBootstrap bootstrap =  new ServerBootstrap(serverChannelFacory);
    bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
        @Override
        public ChannelPipeline getPipeline() throws Exception {
            ChannelPipeline pipeline = Channels.pipeline();
            pipeline.addLast("decoder", new HttpRequestDecoder());
            pipeline.addLast("encoder", new HttpResponseEncoder());
            pipeline.addLast("handler", new YourHandler());
            return null;
        }
    });
    bootstrap.bind(new InetSocketAddress(8080));//启动入口

很明显，入口自然就是bootstrap.bind(),bind方法内会处理下面一部分主要的操作

    public Channel bind(final SocketAddress localAddress) {
        ......
        ChannelHandler binder = new Binder(localAddress, futureQueue);
        ChannelHandler parentHandler = getParentHandler();

        ChannelPipeline bossPipeline = pipeline();
        bossPipeline.addLast("binder", binder);
        if (parentHandler != null) {
            bossPipeline.addLast("userHandler", parentHandler);
        }

        Channel channel = getFactory().newChannel(bossPipeline);
        ......
    }

getFactory()获取的自然是我们前面new ServerBootStrap时的参数NioServerSocketChannelFactory对象，newChannel()的操作是new一个NioServerSocketChannel的对象并返回，传的参数是前面的bossPipeline。所以可以理解这个是针对boss线程的pipeline操作，对应的handler只有binder

    NioServerSocketChannel(
            ChannelFactory factory,
            ChannelPipeline pipeline,
            ChannelSink sink) {

        super(factory, pipeline, sink);

        try {
            socket = ServerSocketChannel.open();
        } catch (IOException e) {