一、介绍

官网：https://netty.io/

Netty是一个NIO客户端服务端框架。

二、要素

ChannelHandler

处理和拦截I/O操作，并且将处理后的数据传至下一个管道

三、源码分析

Netty版本：4.1.44.Final

ChannelHandler调用过程

注册ServerBootstrap.childHandler(ChannelHandler childHandler)

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private void register0(ChannelPromise promise) {
    try {
        // check if the channel is still open as it could be closed in the mean time when the register
        // call was outside of the eventLoop
        if (!promise.setUncancellable() || !ensureOpen(promise)) {
            return;
        }
        boolean firstRegistration = neverRegistered;
        doRegister();
        neverRegistered = false;
        registered = true;

        // Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
        // user may already fire events through the pipeline in the ChannelFutureListener.
        pipeline.invokeHandlerAddedIfNeeded();

        safeSetSuccess(promise);
        pipeline.fireChannelRegistered();
        // Only fire a channelActive if the channel has never been registered. This prevents firing
        // multiple channel actives if the channel is deregistered and re-registered.
        if (isActive()) {
            if (firstRegistration) {
                pipeline.fireChannelActive();
            } else if (config().isAutoRead()) {
                // This channel was registered before and autoRead() is set. This means we need to begin read
                // again so that we process inbound data.
                //
                // See https://github.com/netty/netty/issues/4805
                beginRead();
            }
        }
    } catch (Throwable t) {
        // Close the channel directly to avoid FD leak.
        closeForcibly();
        closeFuture.setClosed();
        safeSetFailure(promise, t);
    }
}

四、相关文章

认真的 Netty 源码解析（一）

认真的 Netty 源码解析（二）

https://www.jianshu.com/nb/22889712

https://www.jianshu.com/p/46861a05ce1e