netty源码分析（2）-初始化Channel

上一节分析了Channel的创建过程，回忆一下，其实newChannel()方法其实只是实例化了一个Channel对象，还未初始化成员变量以及一些列配置.

 @Override
    public T newChannel() {
        try {
            return clazz.newInstance();
        } catch (Throwable t) {
            throw new ChannelException("Unable to create Channel from class " + clazz, t);
        }
    }

入口：initAndRegister() 在调用了newContext()之后紧接着又调用了 init()对channel进行了初始化的过程。以服务端为例，该方法由ServerBootstrap实现

channel = channelFactory.newChannel();
init(channel);

• init(channel)

初始化过程呢，先配置的是AbstractBootstrap的成员变量，这些成员变量会在初始化当中便启用。

    private final Map, Object> options = new LinkedHashMap, Object>();
    private final Map, Object> attrs = new LinkedHashMap, Object>();
    private volatile ChannelHandler handler;

而在子类ServerBootstrap中的定义的成员变量，则会作为连接器ServerBootstrapAcceptor的参数，在客户端与服务器建立新的连接的时候进行实例化，因此这部分成员变量的启用的时间是连接成功后启用。

    private final Map, Object> childOptions = new LinkedHashMap, Object>();
    private final Map, Object> childAttrs = new LinkedHashMap, Object>();
    private final ServerBootstrapConfig config = new ServerBootstrapConfig(this);
    private volatile EventLoopGroup childGroup;
    private volatile ChannelHandler childHandler;

参数基本都来源于用户配置，例如:

 serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_REUSEADDR,true)
                    .childOption(ChannelOption.TCP_NODELAY, true)
                    .attr(AttributeKey.newInstance("attr"),"attr")
                    .childAttr(AttributeKey.newInstance("childAttr"),"childAttr")
                    .handler(new DataServerInitializer0())
                    .childHandler(new DataServerInitializer());

 @Override
    void init(Channel channel) throws Exception {

        //配置AbstractBootstrap.option
        final Map, Object> options = options0();
        synchronized (options) {
            setChannelOptions(channel, options, logger);
        }

        //配置AbstractBootstrap.attr
        final Map, Object> attrs = attrs0();
        synchronized (attrs) {
            for (Entry, Object> e: attrs.entrySet()) {
                @SuppressWarnings("unchecked")
                AttributeKey