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标题: 绑定端口并向Selector注册accept事件 3 [打印本页]

作者: look_w 时间: 2019-4-12 16:53 标题: 绑定端口并向Selector注册accept事件 3

public void bind(ChannelHandlerContext ctx, SocketAddress localAddress,
            ChannelPromise promise) throws Exception {
         ctx.bind(localAddress, promise);
      }

走到这里其实我们发现了其实，还是回到了AbstractChannelHandlerContext#bind(),仍然是先调用了findContextOutbound(),那么其实，整个调用链会一直从pipeline.tail一直往上找到pipeline.head，查看前面章节初始化channel的过程，在实例化NioServerSocketChannel的时候，调用了父类的构造方法，其中AbstractChannel的构造方法实例化了pipeline

protected AbstractChannel(Channel parent) {
         this.parent = parent;
         id = newId();
         unsafe = newUnsafe();
         pipeline = newChannelPipeline();
      }

protected DefaultChannelPipeline newChannelPipeline() {
         return new DefaultChannelPipeline(this);
}

发现，其实是使用了DefaultChannelPipeline。进入该类构造方法,返现实例化的时候创建了，HeadContext 和 TailContext来作为pipeline的头和尾

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;
      }

进入HeadContext#bind()方法，发现其实是调用了unsafe的方法

@Override
         public void bind(
                  ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise)
                  throws Exception {
            unsafe.bind(localAddress, promise);
         }

经过分析该成员变量是与pipeline一样在AbstractChannel的构造方法中被实例化。其实就是NioServerSocketChannel的实例化过程。其中就进行了成员变量AbstractNioChannel.readInterestOp初始化的，其值就是SelectionKey.OP_ACCEPT事件

public NioServerSocketChannel(ServerSocketChannel channel) {
         //初始化过程传入了Selecor事件：accept
         super(null, channel, SelectionKey.OP_ACCEPT);
         config = new NioServerSocketChannelConfig(this, javaChannel().socket());
      }

protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
         super(parent);
         this.ch = ch;
         //初始化事件成员变量
         this.readInterestOp = readInterestOp;
         try {
            ch.configureBlocking(false);
         } 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);
         }
}

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