ChannelHandler中异常的获取与处理是通过继承重写exceptionCaught方法来实现的，本篇文章我们对ChannelPipeline中exceptionCaught异常事件的传播进行梳理分析
1、出站事件的传播示例
首先我们继续在之前的代码上进行改造，模拟异常事件的传播
```
public class ServerApp {
public static void main(String[] args) {
EventLoopGroup boss = new NioEventLoopGroup();
EventLoopGroup work = new NioEventLoopGroup(2);
try {
ServerBootstrap bootstrap = new ServerBootstrap();
bootstrap.childOption(ChannelOption.SO_SNDBUF,2);
bootstrap.group(boss, work).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
// p.addLast(new LoggingHandler(LogLevel.INFO));