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();
         }
     }
 }