Netty：ChannelHandler的两个生命周期监听事件方法：handlerAdded 和 handlerRemoved

说明

io.netty.channel.ChannelHandler有两个生命周期监听事件方法：

handlerAdded(ChannelHandlerContext ctx)：当ChannelHandler被添加到实际的上下文、并且已经准备就绪等待处理事件的时候被调用。
handlerRemoved(ChannelHandlerContext ctx)：当ChannelHandler从实际的上下文被移除、并且不能再处理事件的时候被调用。

示例

服务端代码片段

package com.thb.power.server;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

/**
 * 服务端的主函数
 * @author thb
 *
 */
public class MainStation {
	
	static final int PORT = Integer.parseInt(System.getProperty("port", "22335"));

	public static void main(String[] args) throws Exception {
		// 配置服务器
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap b =  new ServerBootstrap();
			b.group(bossGroup, workerGroup)
			 .channel(NioServerSocketChannel.class)
			 .option(ChannelOption.SO_BACKLOG, 100)
			 .handler(new LoggingHandler(LogLevel.INFO))
			 .childHandler(new MainStationInitializer());
			
			// 启动服务端
			ChannelFuture f = b.bind(PORT).sync();
			
			// 等待直到server socket关闭
			f.channel().closeFuture().sync();
		} finally {
			// 关闭所有event loops以便终止所有的线程
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
		}
	}

}

package com.thb.power.server;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class MainStationInitializer extends ChannelInitializer<SocketChannel> {

	 @Override
	 public void initChannel(SocketChannel ch) throws Exception {
		 ChannelPipeline p = ch.pipeline();
		 
		 p.addLast(new LoggingHandler(LogLevel.INFO));
		 p.addLast(new ServerHandler());
	 }
}

package com.thb.power.server;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class ServerHandler extends ChannelInboundHandlerAdapter {

	@Override
	public void handlerAdded(ChannelHandlerContext ctx) {
		System.out.println(ctx.handler() + " added");		
	}
	
	@Override
	public void handlerRemoved(ChannelHandlerContext ctx) {
		System.out.println(ctx.handler() + " removed");
	}
}