5、netty第四个例子，空闲检测handle

netty可支持空闲检测的处理器，用于心态检测，当服务器端超出等待时间，没发生事件时，会触发handler中的方法 userEventTriggered。

initializer

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.timeout.IdleStateHandler;

import java.util.concurrent.TimeUnit;

public class MyServerInitlalizer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline  = ch.pipeline();

        //空闲事件处理器  读空闲5s    写空闲3s   读写空闲7s  
        pipeline.addLast(new IdleStateHandler(5,7,3,TimeUnit.SECONDS)); //空闲检测   在一定时间间隔内 没有读写
        pipeline.addLast(new MyServerHandler());//自定义的空闲事件处理器

    }
}

handler

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandler;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.timeout.IdleStateEvent;

public class MyServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        //super.userEventTriggered(ctx, evt);
        if ( evt instanceof IdleStateEvent) {//如果是一个空闲状态
            IdleStateEvent event = (IdleStateEvent) evt;

            String  eventType = null;

            switch (event.state()){
                case READER_IDLE:
                    eventType = "读空闲";
                    break;
                case WRITER_IDLE:
                    eventType = "写空闲";
                    break;
                case ALL_IDLE:
                    eventType = "读写空闲";
                    break;
            }

            System.out.println(ctx.channel().remoteAddress() + "超时事件: " + eventType);

            ctx.channel().close();
        }
    }
}