SimpleChannelInboundHandler中channelread和channelread0的区别

先看channelRead方法，直接上源码

public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    boolean release = true;

    try {
        if (this.acceptInboundMessage(msg)) {
            this.channelRead0(ctx, msg);
        } else {
            release = false;
            ctx.fireChannelRead(msg);
        }
    } finally {
        if (this.autoRelease && release) {
            ReferenceCountUtil.release(msg);
        }

    }

}

再看channelRead0方法，只有一行：

protected abstract void channelRead0(ChannelHandlerContext var1, I var2) throws Exception;

可以很明显的看到，channelRead 是public 类型，可以被外部访问；而channelRead0是protected类型，只能被当前类及其子类访问。

channelRead中调用了channelRead0，那么channelRead又额外多做了什么呢？

很明显做了一个消息类型检查，判断是否会传递到下一个handler