Netty源码 新连接处理

上文我们阐述了Netty的Reactor模型。在Reactor模型的第二阶段，Netty会处理各种io事件。对于客户端的各种请求就是在这个阶段去处理的。本文便来分析一个新的连接是如何被处理的。

代码的入口就从read方法开始。这里的unsafe的类型是NioMessageUnsafe，在服务端启动时就确定下来了。 

if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
                unsafe.read();
                if (!ch.isOpen()) {
                    // Connection already closed - no need to handle write.
                    return;
                }
            }

 我们省去部分代码，read方法逻辑非常简单。就是一个读出加处理的过程

public void read() {
            assert eventLoop().inEventLoop();
            final ChannelConfig config = config();
            final ChannelPipeline pipeline = pipeline();
            final RecvByteBufAllocator.Handle allocHandle = unsafe().recvBufAllocHandle();
            allocHandle.reset(config);

            boolean closed = false;
            Throwable exception = null;
                do {
                    //读取消息
                    int localRead = doReadMessages(readBuf);
                    if (localRead == 0) {
                        break;
                    }
                    if (localRead < 0) {
                        closed = true;
                        break;
                    }
                    allocHandle.incMessagesRead(localRead);
                } while (allocHandle.continueReading());

            int size = readBuf.size();
            for (int i = 0; i < size; i ++) {
                readPending = false;
                //循环处理消息
                pipeline.fireChannelRead(readBuf.get(i));
            }
            readBuf.clear();
            allocHandle.readComplete();
            //触发读取完毕事件
            pipeline.fireChannelReadComplete();
    }

 1.读取消息

protected int doReadMessages(List