网络I/o编程模型18 netty通过websocket实现服务，客户端通信

一 需求描述

基于websocket的全双工的长连接，实现客户端和服务端之间信息的交互。比如客户端浏览器和服务器会相互感知，比如服务器关闭了，浏览器会感知；同样浏览器关闭了，服务器也会感知。

二 代码实现

1.服务端

package com.ljf.netty.netty.websocket;

import com.ljf.netty.netty.heartbeat.MyServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
import io.netty.handler.timeout.IdleStateHandler;

import java.util.concurrent.TimeUnit;

/**
 * @ClassName: NettyWebSocketServer
 * @Description: TODO
 * @Author: liujianfu
 * @Date: 2022/06/04 12:00:07
 * @Version: V1.0
 **/
public class NettyWebSocketServer {
    public static void main(String[] args) {
        //创建两个线程组
        EventLoopGroup bossGroup=new NioEventLoopGroup(1);
        EventLoopGroup workerGroup=new NioEventLoopGroup();//8个NioEventLoop
        try {
            ServerBootstrap serverBootstrap=new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup);
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.handler(new LoggingHandler(LogLevel.INFO));
            serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ChannelPipeline pipeline=ch.pipeline();
                    //因为基于http协议，使用http的编码和解码器
                    pipeline.addLast(new HttpServerCodec());
                    //是以块方式写，添加chunkedwritehandler 处理器
                    pipeline.addLast(new ChunkedWriteHandler());
                    //当浏览器发送大量数据时，就会发出多次http请求，http数据在传输过程中是分段的。
                    pipeline.addLast(new HttpObjectAggregator(8192));
                    //websocket 它的数据是以帧的形式传递；WebSocketSeverProtocolHandler 核心功能是将http协议升级为ws协议，保持长连接
                    //浏览器请求是，ws://localhost:6000/hello 表示请求的uri
                    pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));
                    //自定义的handler，处理业f务逻辑
                    pipeline.addLast(new MyTextWebSocketFrameHandler());
                }
            });
            //启动服务器
            ChannelFuture channelFuture = serverBootstrap.bind("127.0.0.1",6666).sync();
            channelFuture.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

}

2.自定义处理类

package com.ljf.netty.netty.websocket;

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;

import java.time.LocalDateTime;

/**
 * @ClassName: MyTextWebSocketFrameHandler
 * @Description: TODO  这里的TextWebSocketFrame 表示类型，表示一个文本帧
 * @Author: liujianfu
 * @Date: 2022/06/04 16:36:39
 * @Version: V1.0
 **/
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
        System.out.println("服务器收到的信息:"+msg.text());
        //回复信息
        ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器时间:"+ LocalDateTime.now()+""+msg.text()));
    }
    //有web客户端连接后，触发的方法
    public void handlerAdded(ChannelHandlerContext ctx){
        //id 表示唯一的值，LongText是唯一的；  shortText不是唯一
        System.out.println("handlerAdded 被调用:"+ctx.channel().id().asLongText());
        System.out.println("handlerAdded 被调用:"+ctx.channel().id().asShortText());
    }
    //有web客户端连接断开后，触发的方法
    public void handlerRemoved(ChannelHandlerContext ctx){
        System.out.println("handlerRemove 被调用:"+ctx.channel().id().asLongText());
    }
    //发生异常
    public void exceptionCaught(ChannelHandlerContext ctx,Throwable cause){
        System.out.println("异常发生:"+cause.getMessage());
        ctx.close();
    }

}

3. 前端页面

<!doctype html>
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
  <script>
  var socket;
  //判断当前浏览器是否支持websocket
  if(window.WebSocket){
	  socket=new WebSocket("ws://127.0.0.1:6666/hello");
	  //相当于channelReado,ev收到的服务器回送的消息
	  socket.onmessage=function(ev){
         var rt=document.getElementById("responseText");
		 rt.value=rt.value+"\n"+ev.data;
	  }
	  //相当于连接开启(感知道连接开启)
	  socket.onopen=function(ev){
		  var rt=document.getElementById("responseText");
		  rt.value="连接开启了....";
	  }
     //相当于连接关闭
	 socket.onclose=function(ev){
		 var rt=document.getElementById("responseText");
		  rt.value=rt.value+"\n"+" 连接关闭了....";
	 }
  }
  else{
	  alert("当前浏览器不支持websocket");

  }
  //发送消息道服务器
  function sendInfo(message){
	  alert(message);
      if(!window.socket){
		  return ; //先判断socket是否创建好
	  }
	  if(socket.readyState==WebSocket.OPEN){
         //通过socket发送消息
		 socket.send(message);
	  }
	  else{
		  alert("连接没有开启...");
	  }
  }
  </script>
 </head>
 <body>
  <form onsubmit="return false">
  <textarea name="message" style="height:300px;width:300px"></textarea>
  <input type="button" value="发送消息" onclick="sendInfo(this.form.message.value)">
  <textarea id="responseText" style="height:300px;width:300px"></textarea>
  <input type="button" value="清空内容" onclick="document.getElementById('responseText').value=''">
  </form>
 </body>
</html>

4.查询结果 

1.服务端

 

2.页面