netty4.1.6源码2-------创建服务端的channel

1. netty在哪里调用jdk底层的socket去创建netty服务端的socket。
2. 在哪里accept连接。
服务端的启动：
1. 调用jdk底层的api去创建jdk的服务端的channel。Netty封装成自己的channel同时创建一些组件绑定在这个channel上面。
2. 初始化服务端的channel。
3. 注册selector，netty将jdk底层的channel注册到事件轮询器selector上面，并把服务端的channel作为attachment附加到jdk底层的channel上面，有事件轮询出来的时候就可以直接拿这个attachment，这个attachment就是netty封装的服务端的channel。
4. 端口绑定，调用jdk底层的api作为端口的监听。

1. 创建服务端的channel：

ChannelFuture f = b.bind(8888).sync();//服务端创建channel的入口
final ChannelFuture regFuture = initAndRegister(); //创建服务端的channel

final ChannelFuture initAndRegister() {        
Channel channel = null;        
try {            
   channel = channelFactory.newChannel(); //.channel方法设置channelFactory，channelFactory是ReflectiveChannelFactory            
   init(channel);        
}

public class ReflectiveChannelFactory<T extends Channel> implements ChannelFactory<T> {
public ReflectiveChannelFactory(Class<? extends T> clazz) {
   if (clazz == null) {
       throw new NullPointerException("clazz");
   }
   this.clazz = clazz;
}    
        @Override
    public T newChannel() { //newChannel方法
        try {
            return clazz.newInstance(); //通过反射创建channel，clazz是NioServerSocketChannel.class，newInstance()调用的是构造函数
        } catch (Throwable t) {
            throw new ChannelException("Unable to create Channel from class " + clazz, t);
        }
    }
}

ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class) //分析.channel方法，传入NioServerSocketChannel通过反射方式调用NioServerSocketChannel类的构造函数

AbstractBootstrap类：    
public B channel(Class<? extends C> channelClass) { //channelClass是传进来的NioServerSocketChannel.class
        if (channelClass == null) {
            throw new NullPointerException("channelClass");
        }
        return channelFactory(new ReflectiveChannelFactory<C>(channelClass));  //通过ReflectiveChannelFactory构造函数把channelClass封装成ReflectiveChannelFactory，设置channelFactory
    }

    public B channelFactory(ChannelFactory<? extends C> channelFactory) {
        if (channelFactory == null) {
            throw new NullPointerException("channelFactory");
        }
        if (this.channelFactory != null) {
            throw new IllegalStateException("channelFactory set already");
        }
        this.channelFactory = channelFactory; //设置channelFactory
        return (B) this;
    }

NioServerSocketChannel构造函数：

private static final SelectorProvider DEFAULT_SELECTOR_PROVIDER = SelectorProvider.provider();
    private static ServerSocketChannel newSocket(SelectorProvider provider) {
        try {
            return provider.openServerSocketChannel();
        } catch (IOException e) {
            throw new ChannelException("Failed to open a server socket.", e);
        }
    }
public NioServerSocketChannel() { //构造函数
    this(newSocket(DEFAULT_SELECTOR_PROVIDER)); //newSocket创建jdk底层的Channel，服务端的channel就创建完毕了
}

public NioServerSocketChannel(ServerSocketChannel channel) {
        super(null, channel, SelectionKey.OP_ACCEPT);
        config = new NioServerSocketChannelConfig(this, javaChannel().socket());  // this是NioServerSocketChannel也就是netty服务端的channel，
}

super(null, channel, SelectionKey.OP_ACCEPT); //跟进去
AbstractNioChannel类：
    protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
        super(parent);
        this.ch = ch; //通过newSocket创建出来的jdk底层的channel，
        this.readInterestOp = readInterestOp;
        try {
            ch.configureBlocking(false);//设置服务端的channel非阻塞模式，
        } catch (IOException e) {
            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);
        }
    }

//channel有服务端和客户端的channel，都继承自AbstractChannel，
protected AbstractChannel(Channel parent) {
        this.parent = parent;
        id = newId();//channel唯一的表示
        unsafe = newUnsafe();//channel底层tcp相关的操作
        pipeline = newChannelPipeline();
}