netty源码分析-server启动-initAndRegister

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本文包括以下内容
  1. initAndRegister-createChannel分析
  2. initAndRegister-createChannel分析
  3. ChannelInitializer分析
创建channel-server端bind()调用链如下

  
sever端启动主要处理都在bind(）处理中，其中主要代码如下
AbstractBootstrap
private ChannelFuture doBind(final SocketAddress localAddress) {
        final ChannelFuture regFuture = initAndRegister();
        final Channel channel = regFuture.channel();
        if (regFuture.cause() != null) {
            return regFuture;
        }

        final ChannelPromise promise;
        if (regFuture.isDone()) {
            promise = channel.newPromise();
            doBind0(regFuture, channel, localAddress, promise);
        } else {
            // Registration future is almost always fulfilled already, but just in case it's not.
            promise = new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE);
            regFuture.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture future) throws Exception {
                    doBind0(regFuture, channel, localAddress, promise);
                }
            });
        }

        return promise;
    }
其中最重要的两个部分已经标出，先来分析一下initAndRegister()

分析initAndRegister方法
时序图如下

    final ChannelFuture initAndRegister() {
        Channel channel;
        try {
//创建channel,并配置其主要属性
            channel = createChannel();
        } catch (Throwable t) {
            return VoidChannel.INSTANCE.newFailedFuture(t);
        }

        try {
//初始化channel
            init(channel);
        } catch (Throwable t) {
            channel.unsafe().closeForcibly();
            return channel.newFailedFuture(t);
        }
//创建ChannelPromise
        ChannelPromise regFuture = channel.newPromise();
        channel.unsafe().register(regFuture);
        if (regFuture.cause() != null) {
            if (channel.isRegistered()) {
                channel.close();
            } else {
                channel.unsafe().closeForcibly();
            }
        }
        return regFuture;
    }
1.createChannel分析
ServerBootstrap：
    Channel createChannel() {
        EventLoop eventLoop = group().next();
        return channelFactory().newChannel(eventLoop, childGroup);
    }
ServerBootstrapChannelFactory
        @Override
        public T newChannel(EventLoop eventLoop, EventLoopGroup childGroup) {
            try {
//class=NioSocketChannel.class,调用它的构造方法。
                Constructor constructor = clazz.getConstructor(EventLoop.class, EventLoopGroup.class);
                return constructor.newInstance(eventLoop, childGroup);
            } catch (Throwable t) {
                throw new ChannelException("Unable to create Channel from class " + clazz, t);
            }
        }
//调用NioServerSocketChannel构造方法创建实例
    public NioServerSocketChannel(EventLoop eventLoop, EventLoopGroup childGroup) {
//调用父类构造方法
        super(null, eventLoop, childGroup, newSocket(), SelectionKey.OP_ACCEPT);
//创建默认配置
        config = new DefaultServerSocketChannelConfig(this, javaChannel().socket());
    }

    protected AbstractNioMessageServerChannel(
            Channel parent, EventLoop eventLoop, EventLoopGroup childGroup, SelectableChannel ch, int readInterestOp) {
//调用父类构造方法
//此时parent=null 。ch=ServerSocketChannelImp（java原生的）
        super(parent, eventLoop, ch, readInterestOp);
//childGroup赋值
        this.childGroup = childGroup;
    }
    protected AbstractNioMessageChannel(
            Channel parent, EventLoop eventLoop, SelectableChannel ch, int readInterestOp) {
//调用父类构造方法
        super(parent, eventLoop, ch, readInterestOp);
    }

protected AbstractNioChannel(Channel parent, EventLoop eventLoop,     SelectableChannel ch, int readInterestOp) {
//调用父类构造方法
        super(parent, eventLoop);
// 赋值 java SocketChannelImpl
        this.ch = ch;
        this.readInterestOp = readInterestOp;
        try {
//配置java.nio.ServerSocketChannel为非阻塞
            ch.configureBlocking(false);
        } catch (IOException e) {
//异常处理暂时不关注
            try {
                ch.close();
            } catch (IOException e2) {
                if (logger.isWarnEnabled()) {
                    logger.warn(
                            "Failed to close a partially initialized socket.", e2);
                }
            }

            throw new ChannelException("Failed to enter non-blocking mode.", e);
        }
    }
最后调用
    protected AbstractChannel(Channel parent, EventLoop eventLoop) {
        this.parent = parent;
// 非空和兼容校验
        this.eventLoop = validate(eventLoop);
        unsafe = newUnsafe();//初始化unsafe××重要×××
        pipeline = new DefaultChannelPipeline(this);//初始化pipeline××重要×××
    }

AbstractNioChannel
//兼容校验
    protected boolean isCompatible(EventLoop loop) {
        return loop instanceof NioEventLoop;
    }
小结：createChannel创建了 unsafe，pipeline，java.nio.ServerSocketChannel，然后为其属性eventLoop，childGroup，readInterestOp，config 赋值。
eventLoop是什么时候创建的  ？
创建 EventLoopGroup时创建的

2.init分析
void init(Channel channel) throws Exception {
        final Map, Object> options = options();
//options value= {SO_BACKLOG=128}
        synchronized (options) {
            channel.config().setOptions(options);
        }

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