纯netty实现websocket聊天，http协议页面展现，代码分析

港控/mmm° 2022-04-10 02:37 73阅读 0赞

### 上篇文章我介绍了netty聊天室的实现效果与实现需求，这篇文章我会给大家展示代码 ###

>  注：部分代码直接使用netty权威指南中的示例代码

netty权威指南附源代码下载地址：[https://download.csdn.net/download/qq\_37316272/10872031][https_download.csdn.net_download_qq_37316272_10872031]

netty聊天室在线演示地址：[https://blog.csdn.net/qq\_37316272/article/details/85130365][https_blog.csdn.net_qq_37316272_article_details_85130365]

主启动类代码

package com.ning.netty;
    
    import java.util.concurrent.ConcurrentHashMap;
    import java.util.concurrent.ConcurrentMap;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.ChannelPipeline;
    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.stream.ChunkedWriteHandler;
    
    public class WebSocketServer {
    	public static ConcurrentMap<Object, Object> channels = new ConcurrentHashMap<>();
    	public void run(int port) throws Exception{
    		NioEventLoopGroup bossGroup = new NioEventLoopGroup();
    		NioEventLoopGroup workerGroup = new NioEventLoopGroup();
    		try {
    			ServerBootstrap b = new ServerBootstrap();
    			b.group(bossGroup, workerGroup)
    				.channel(NioServerSocketChannel.class)
    				.childHandler(new ChannelInitializer<SocketChannel>() {
    
    					@Override
    					protected void initChannel(SocketChannel ch) throws Exception {
    						ChannelPipeline pipline = ch.pipeline();
    						pipline.addLast("http-codec",new HttpServerCodec());
    						pipline.addLast("aggregator",new HttpObjectAggregator(165536));
    						ch.pipeline().addLast("http-chunked",new ChunkedWriteHandler());
    						pipline.addLast("handler",new WebSocketServerHandler());
    					}
    				});
    			Channel ch = b.bind(port).sync().channel();
    			System.out.println("Web socket 启动完成，端口号："+port);
    			System.out.println("http://localhost:"+port+"/");
    			ch.closeFuture().sync();
    		} finally {
    			bossGroup.shutdownGracefully();
    			workerGroup.shutdownGracefully();
    		}
    	}
    	public static void main(String[] args) throws Exception {
    		new WebSocketServer().run(8099);
    	}
    }

注意这里我定义了一个 ConcurrentMap用来存放用户和对应的channel连接。

主要看handler代码实现

首先定义静态代码存放位置，主要用于返回页面的html代码：

private String basePath;
    	{
    		String os = System.getProperty("os.name");
    		if(os.toLowerCase().startsWith("win")){  
    			basePath = "G:/myeclipsework/nettychat/src/main/resources/static/";
    		}else{
    			basePath = "/opt/nettychat/static/";
    		}
    	}

如果接受到的请求是http请求，则去到定义的静态目录下寻找资源：

@Override
    	protected void messageReceived(ChannelHandlerContext ctx, Object msg) throws Exception {
    		if (msg instanceof FullHttpRequest) {
    			handleHttpRequest(ctx, (FullHttpRequest) msg);
    		} else if (msg instanceof WebSocketFrame) {
    			handleWebSocketFrame(ctx, (WebSocketFrame) msg);
    		}
    	}

如果请求是http请求，请求地址是网站根路径，直接返回index.html，否则就按照请求的路径寻找资源。如果是websocket请求则创建握手处理器类，注意因为消息中我需要包含base64编码的图片，是上万长度的字符串所以这里创建握手处理器类讲传输长度设置为65536\*5，处理websocket连接。

private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception {
    		if (!req.getDecoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
    			String uri = req.getUri();
    			File file;
    			if(uri.equals("/")){
    				file = new File(basePath+"/index.html");
    			}else{
    				file = new File(basePath+uri);
    			}
    			RandomAccessFile randomAccessFile = null;
    			try {
    				randomAccessFile = new RandomAccessFile(file, "r");// 以只读的方式打开文件
    			} catch (FileNotFoundException fnfe) {
    				return;
    			}
    			long fileLength = randomAccessFile.length();
    			HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);
    			setContentLength(response, fileLength);
    			setContentTypeHeader(response, file);
    			if (isKeepAlive(req)) {
    				response.headers().set(CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
    			}
    			ctx.write(response);
    			ChannelFuture sendFileFuture;
    			sendFileFuture = ctx.write(new ChunkedFile(randomAccessFile, 0, fileLength, 8192),
    					ctx.newProgressivePromise());
    			sendFileFuture.addListener(new ChannelProgressiveFutureListener() {
    				@Override
    				public void operationProgressed(ChannelProgressiveFuture future, long progress, long total) {
    					if (total < 0) { // total unknown
    						System.err.println("Transfer progress: " + progress);
    					} else {
    						System.err.println("Transfer progress: " + progress + " / " + total);
    					}
    				}
    				
    				@Override
    				public void operationComplete(ChannelProgressiveFuture future) throws Exception {
    					System.out.println("Transfer complete.");
    				}
    			});
    			ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
    			if (!isKeepAlive(req)) {
    				lastContentFuture.addListener(ChannelFutureListener.CLOSE);
    			}
    			return;
    		}
    		WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
    				"ws://localhost:8099/websocket", null, false,65536*5);
    		handshaker = wsFactory.newHandshaker(req);
    		if (handshaker == null) {
    			WebSocketServerHandshakerFactory.sendUnsupportedWebSocketVersionResponse(ctx.channel());
    		} else {
    			handshaker.handshake(ctx.channel(), req);
    		}
    	}

先看一下网页代码实现吧：

<!DOCTYPE html>
    <html>
    	<head>
    		<meta charset="utf-8">
    		<title>Netty聊天室-信息时代-技术博客</title>
    		<style>
    			*{padding: 0;margin: 0;list-style: none;}
    			html,body{width: 100%;height: 100%;}
    			#useUl li{
    				list-style: none;
    				cursor: pointer;
    				height: 50px;
    				width: 250px;
    				border-bottom: 1px solid #ccc;
    			}/* #ff784d */
    			#useUl li img{
    				width: 50px;
    				height: 50px;
    				border-radius: 50%;
    				vertical-align: middle;
    				margin-right: 20px;
    			}
    			#loginDiv{
    				padding: 25px;
    				width: 260px;
    				height: 400px;
    				border: 1px solid #ccc;
    				margin: 100px auto;
    			}
    			#headImg{
    				width: 100px;
    				height: 100px;
    				border-radius: 50%;
    				margin: auto;
    				line-height: 100px;
    				text-align: center;
    				cursor: pointer;
    			}
    			#username{
    				width: 95%;
    				display: block;
    				height: 30px;
    				border: 1px solid #ccc;
    				padding-left: 5%;
    				margin-top: 30px;
    			}
    			#login{
    				height: 30px;
    				margin-top: 30px;
    				width: 100%;
    				background: #ff784d;
    				border: none;
    				cursor: pointer;
    				outline: none;
    				color: #fff;
    			}
    			#login:hover{
    				background: #ff521b;
    			}
    			#chatDiv{
    				width: 100%;
    				height: 100%;
    				display: none;
    			}
    			#userDiv{
    				width: 250px;
    				min-height: 400px;
    				border: 1px solid #ccc;
    				float: right;
    				position: absolute;
    				top: 0;
    				right: 0;
    				padding: 20px;
    			}
    			#mesDiv{
    				width: 600px;
    				height: 500px;
    				border: 1px solid #ccc;
    				position: absolute;
    				left: 30%;
    				top: 50%;
    				margin-top: -250px;
    			}
    			#sendBtn{
    				width: 60px;
    				height: 25px;
    				background: #ff784d;
    				border: none;
    				cursor: pointer;
    				outline: none;
    				color: #fff;
    			}
    			#sendBtn:hover{
    				background: #ff521b;
    			}
    			.msgDiv{
    				padding: 0 10px;
    				margin: 5px 0;
    			}
    			.msgDiv .headImg{
    				width: 40px;
    				height: 40px;
    				border-radius: 50%;
    				border:1px solid #ccc;
    				margin-right:10px;
    				vertical-align: top;
    			}
    			.msgDiv .msgWrap{
    				display: inline-block;
    				max-width: 70%;
    			}
    			.msgDiv .userN{
    				color: #999;
    			}
    			.langMsg{
    				background: #e2e2e2;
    				padding: 10px;
    				border-radius: 5px;
    				color: #333;
    			}
    			.rightMes .headImg{
    				margin-left: 10px;
    				margin-right: 0;
    			}
    			.rightMes{
    				text-align: right;
    			}
    			.rightMes .langMsg{
    				background: #5FB878;
    				color:#fff
    			}
    			#mes{
    				overflow-y: scroll;
    			}
    			#mes::-webkit-scrollbar {
    				width: 4px;     
    				height: 1px;
    			}
    			#mes::-webkit-scrollbar-thumb {
    				background: #fff;
    			}
    			#mes::-webkit-scrollbar-track {
    				background: #fff;
    			}
    			#mes:hover::-webkit-scrollbar-thumb {
    				background: #ff3e00;
    			}
    			#mes:hover::-webkit-scrollbar-track {
    				background: rgba(128, 128, 128, 0.5);
    			}
    		</style>
    	</head>
    	<body>
    		<canvas id="canvas" style="display: none">
    			
    		</canvas>
    		<div id="loginDiv">
    			<div id="headImg" style="padding: 10px;border:1px solid #ccc">点击上传头像</div><input type="file" id="fileInp" style="display: none"><input type="text" id="username" placeholder="请输入用户名"><input type="button" id="login" value="登陆">
    			<input type="hidden" id="headInp">
    		</div>
    		<div id="chatDiv">
    			<div id="mesDiv" style="">
    				<div id="topUser" style="border-bottom: 1px solid #ccc;height: 45px;line-height: 30px;padding: 10px;">
    					<img src="/favicon.ico" style="vertical-align: middle;border: 1px solid #ccc;margin-right: 20px;border-radius: 50%;">Netty总群
    				</div>
    				<div id="mes" style="height: 280px;border-bottom: 1px solid #ccc;vertical-align: top;">
    				</div>
    				<div id="mesText" style="height: 130px;padding: 10px;">
    					<p><img src="/image.png" alt="" style="width: 20px;cursor: pointer;" id="chatImg"></p>
    					<textarea id="sendInp" style="font-size: 16px;border: none;overflow: hidden;resize: none;outline: none;width: 100%;height: 80px;"></textarea>
    					<p style="text-align: right;"><input type="button" id="sendBtn" value="发送"></p>
    				</div>
    			</div>
    			<input type="hidden" id="chatInp">
    			<input type="file" id="chatFileInp" style="display: none">
    			<div id="userDiv">
    				<div style="margin: auto;width: 100px;height: 100px;border-radius: 50%;overflow: hidden;">
    					<img src="" id="headSrc" style="width:100px;height: 100px;">
    				</div>
    				<p style="padding: 20px 0;text-align: center;border-bottom: 1px solid #ccc;"><span style="color: #ff521b;" id="us">admin</span></p>
    				<ul id="useUl" style=";vertical-align: top;">
    				</ul>
    			</div>
    		</div>
    	</body>
    	<script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
    	<script>
    		var socket;
    		if(!window.WebSocket){
    			window.WebSokcet = window.MozWebSocket;
    		}
    		if(window.WebSocket){
    			socket = new WebSocket("ws://192.168.1.9:8099/websocket");
    			socket.onmessage = function(event){
    				var res = JSON.parse(event.data);
    				console.log(res);
    				if(res.type == "user"){
    					$("#mes").append('<div class="leftMes msgDiv"><img src="/favicon.ico" class="headImg"><div class="msgWrap"><p class="userN">管理员</p><p class="langMsg">'+res.username+'已登录</p></div></div>');
    					$("#useUl").append("<li flag='0'><img src='/headImg/"+res.headImg+"'>"+res.username+"</li>")
    				}
    				if(res.type == "msg"){
    					$("#mes").append('<div class="leftMes msgDiv"><img src="/headImg/'+res.headImg+'" class="headImg"><div class="msgWrap"><p class="userN">'+res.username+'</p><p class="langMsg">'+res.msg+'</p></div></div>');
    				}
    				if(res.type == "logout"){
    					$("#mes").append('<div class="leftMes msgDiv"><img src="/headImg/'+res.headImg+'" class="headImg"><div class="msgWrap"><p class="userN">管理员</p><p class="langMsg">'+res.username+'已退出</p></div></div>');
    					$("#useUl li").each(function(){
    						if($(this).text() == res.username){
    							$(this).remove();
    						}
    					});
    				}
    				if(res.type == "img"){
    					$("#mes").append('<div class="leftMes msgDiv"><img src="/headImg/'+res.headImg+'" class="headImg"><div class="msgWrap"><p class="userN">'+res.username+'</p><p class="langMsg"><img src="/chatimg/'+res.chatImg+'" onload="scrollBottom()" style="width:100px"></p></div></div>');
    				}
    				$("#mes").scrollTop($("#mes").prop("scrollHeight"),200);
    			}
    			socket.onopen = function(event){
    				console.log("打开WebSocket服务正常，浏览器支持WebSoket");
    			}
    			socket.onclose = function(evnet){
    				console.log("WebSocket关闭！");
    			}
    		}
    		$("#headImg").click(function(){
    			$("#fileInp").click();
    		});
    		$("#chatImg").click(function(){
    			$("#chatFileInp").click();
    		});
    		$("#fileInp").change(function(){
    			var f = $(this)[0].files[0];
    			var reader = new FileReader();
    			if(f){
    				reader.readAsDataURL(f);
    				reader.onload = function(e){
    					var res = reader.result;
    					$("#headImg").html("<img id='HEADIMG' style='width:100px;border-radius:50%;height:100px' src='"+res+"'>");
    					/* base64转canvas */
    					var _img = new Image();
    					_img.src = res;
    					_img.onload = function(){
    						var can = document.getElementById("canvas");
    						var w = $("#HEADIMG").width();
    						var h = $("#HEADIMG").height();
    						var ctx = can.getContext("2d");
    						$(can).attr("width",w);
    						$(can).attr("height",h);
    						$(can).width(w);
    						$(can).height(h)
    						ctx.clearRect(0,0,$(can).width(),$(can).height())
    						ctx.drawImage(_img, 0, 0,100,100);
    						var base64 = can.toDataURL("image/jpeg");
    						$("#headInp").val(base64);
    					}
    					/*  */
    				}
    			}
    		});
    		function scrollBottom(){
    			$("#mes").scrollTop($("#mes").prop("scrollHeight"),200);
    		}
    		$("#chatFileInp").change(function(){
    			var f = $(this)[0].files[0];
    			var reader = new FileReader();
    			if(f){
    				reader.readAsDataURL(f);
    				reader.onload = function(e){
    					var res = reader.result;
    					$("#mes").append('<div class="rightMes msgDiv"><div class="msgWrap"><p class="userN">我</p><p class="langMsg"><img src="'+res+'" style="width:100px"></p></div><img src="'+$("#headSrc").attr("src")+'" onload="scrollBottom()" class="headImg"></div>');
    					var _img = new Image();
    					_img.src = res;
    					_img.onload = function(){
    						var can = document.getElementById("canvas");
    						var w = _img.width;
    						var h = _img.height;
    						if(w > 700){
    							w = 400;
    							h = 300;
    						}
    						$(can).attr("width",w);
    						$(can).attr("height",h);
    						$(can).width(w);
    						$(can).height(h)
    						var ctx = can.getContext("2d");
    						ctx.drawImage(_img, 0, 0,w,h);
    						var base64 = can.toDataURL("image/jpeg");
    						$("#chatInp").val(base64);
    						var list = $("#useUl li[flag=1]");
    						var len = list.length;
    						var str = "";
    						if(len > 0){
    							for(var i = 0;i < len;i++){
    								if(i != len -1){
    									str += list.eq(i).text()+",";
    								}else{
    									str += list.eq(i).text()
    								}
    							}
    						}
    						var isSelect = str == "" ? 0 : 1;
    						var param = {
    							"isSelect":isSelect,
    							"type":"img",
    							"user":str,
    							"username":$("#username").val().trim(),
    							"chatImg":$("#chatInp").val()
    						}
    						socket.send(JSON.stringify(param));
    					}
    				}
    			}
    		});
    		$("#sendBtn").click(function(){
    			var list = $("#useUl li[flag=1]");
    			var len = list.length;
    			var str = "";
    			if(len > 0){
    				for(var i = 0;i < len;i++){
    					if(i != len -1){
    						str += list.eq(i).text()+",";
    					}else{
    						str += list.eq(i).text()
    					}
    				}
    			}
    			var isSelect = str == "" ? 0 : 1;
    			var param = {
    				"isSelect":isSelect,
    				"type":"msg",
    				"user":str,
    				"username":$("#username").val().trim(),
    				"msg":$("#sendInp").val().trim()
    			}
    			$("#mes").append('<div class="rightMes msgDiv"><div class="msgWrap"><p class="userN">我</p><p class="langMsg">'+$("#sendInp").val().trim()+'</p></div><img src="'+$("#headSrc").attr("src")+'" class="headImg"></div>');
    			$("#mes").scrollTop($("#mes").prop("scrollHeight"),200);
    			socket.send(JSON.stringify(param));
    		});
    		$(document).on("click","#useUl li",function(){
    			if($(this).attr("flag") == "0"){
    				$(this).attr("flag",1)
    				$(this).css("color","red");
    			}else{
    				$(this).css("color","black")
    				$(this).attr("flag",0)
    			}
    		});
    		$("#login").click(function(){
    			var user = $("#username").val().trim();
    			if(user == "" || $("#headInp").val() == ""){
    				alert("请输入用户名，并上传头像");
    				return false;
    			}
    			socket.send(JSON.stringify({"type":"user","username":user,"headImg":$("#headInp").val()}));
    			$("#loginDiv").hide();
    			$("#chatDiv").show();
    			$("#mes").append('<div class="leftMes msgDiv"><img src="/favicon.ico" class="headImg"><div class="msgWrap"><p class="userN">管理员</p><p class="langMsg">欢迎登陆：'+user+'</p></div></div>');
    			$("#us").text(user);
    			$("#headSrc").attr("src",$("#headInp").val());
    			$("#mes").scrollTop($("#mes").prop("scrollHeight"),200);
    		});
    	</script>
    </html>

网页一加载完成就会用js进行websocket连接，这时，服务器与浏览器已经建立了连接，但我要实现的是用户带头像登陆功能，所以暂时不能存储用户的信息和channel。当用户选择图片之后，首先将图片进行base64绘制到canvas上，目的是将图片转化成统一的jpg格式，方便服务器统一解析。发送的数据格式为json数据字符串。请注意是将json对象字符串化。JSON.stringify()方法。下面是服务器的接受消息的方法。

接受的消息首先是字符串，需要把字符串转化为对象，所以用fastjson转化成Map对象，每个消息上我都定义了消息类型，如果是user类型，则是用户登录，如果是logout类型则是用户退出，其他都是消息，消息分类普通消息和图片消息

private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) throws Exception{
    		if (frame instanceof CloseWebSocketFrame) {
    			handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
    			return;
    		}
    		if (frame instanceof PingWebSocketFrame) {
    			ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
    			return;
    		}
    		if (!(frame instanceof TextWebSocketFrame)) {
    			throw new UnsupportedOperationException(
    					String.format("%s frame types not supported", frame.getClass().getName()));
    		}
    		String request = ((TextWebSocketFrame) frame).text();
    		System.out.println(request);
    		Map<String, Object> map = (Map<String, Object>) JSON.parse(request);
    		if (map.get("type").equals("user")) {
    			String uuid = saveImg(map,"headimg","headImg");
    			map.put("headImg", uuid+".jpg");
    			for (Map.Entry<Object, Object> c : WebSocketServer.channels.entrySet()) {
    				Map<String,Object> key = (Map<String, Object>) c.getKey();
    				Map<String, Object> maps = new HashMap<String, Object>();
    				maps.put("type", "user");
    				maps.put("username", key.get("username"));
    				maps.put("headImg", key.get("headImg"));
    				ctx.channel().writeAndFlush(new TextWebSocketFrame(JSON.toJSONString(maps)));
    			}
    			request = JSON.toJSONString(map);
    			sendAllUser(request);
    			WebSocketServer.channels.put(map, ctx.channel());
    		} else {
    			if(map.get("type").equals("img")){
    				String uuid = saveImg(map,"chatimg","chatImg");
    				map.put("chatImg", uuid+".jpg");
    			}
    			Map<String, Object> myInfo = getMyInfo(ctx);
    			map.put("headImg", myInfo.get("headImg"));
    			request = JSON.toJSONString(map);
    			if (map.get("isSelect").equals(0)) {
    				sendAllNotMe(ctx.channel(), request);
    			} else {
    				sendSelectUser(map.get("user").toString(), request);
    			}
    		}
    	}

当用户登录的时候发送得是用户名，头像键值对字符串，所以把用户头像的base64字符串转化成图片存在本地，并把用户头像属性换成本地存放的文件名称，并且把当前登陆的用户信息发送给其他已登录的用户，提示新用户登陆，并且将所有已登录的用户发送给这个新登录的用户，提示当前所有已登录的用户。给当前所有登陆用户发送完消息后，在将自己的信息放入到map中，这样再有新用户登陆，就会遍历这个map发送消息了。

如果是普通的消息，则看用户是否选中其他用户，如果选中了其他用户，则为私聊，否则群发所有登陆用户。

如果服务器收到图片消息，则首先将base64图片解码成图片，存放于服务器目录下，然后将文件名和发送给其他用户，其他用户展示消息会访问服务器的图片进行展示。

下面是保存图片代码

private String saveImg(Map<String, Object> map,String path,String param) throws IOException, FileNotFoundException {
    		String headImg = map.get(param).toString();
    		headImg = headImg.split(",")[1];
    		
    		Decoder decoder = Base64.getDecoder();
    		byte[] b = decoder.decode(headImg);
    		for (int i = 0; i < b.length; ++i) {
    			if (b[i] < 0) {// 调整异常数据
    				b[i] += 256;
    			}
    		}
    		String uuid = UUID.randomUUID().toString();
    		File dir = new File(basePath+path);
    		if(!dir.exists()){
    			dir.mkdirs();
    		}
    		File file = new File(dir+File.separator+uuid+".jpg");
    		if(!file.exists()){
    			file.createNewFile();
    		}
    		FileChannel chan = new FileOutputStream(file).getChannel();
    		ByteBuffer buf = ByteBuffer.allocate(b.length);
    		buf.put(b);
    		buf.flip();
    		chan.write(buf);
    		chan.close();
    		return uuid;
    	}

这是发送给选中用户的代码

private static void sendSelectUser(String userStr, String msg) {
    		String[] split = userStr.split(",");
    		List<String> list = Arrays.asList(split);
    		for(Map.Entry<Object, Object> en :WebSocketServer.channels.entrySet()){
    			Map<String,Object> key = (Map<String, Object>) en.getKey();
    			if(list.contains(key.get("username"))){
    				((Channel)en.getValue()).writeAndFlush(new TextWebSocketFrame(msg));
    			}
    		}
    	}

发送给所有用户，但不包括自己，因为自己的不用接收自己的消息，当点击发送按钮的时候直接操作dom进行展示即可

private static void sendAllNotMe(Channel ch, String msg) {
    		for (Map.Entry<Object, Object> c : WebSocketServer.channels.entrySet()) {
    			if (!c.getValue().equals(ch)) {
    				((Channel) c.getValue()).writeAndFlush(new TextWebSocketFrame(msg));
    			}
    		}
    	}

当用户刷新页面，或者用户异常，则channel关闭，则视为用户退出，执行下面的代码，页面会提示用户已退出：

@Override
    	public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
    		for (Map.Entry<Object, Object> ent : WebSocketServer.channels.entrySet()) {
    			if (ent.getValue().equals(ctx.channel())) {
    				Map<String,Object> user = (Map<String,Object>) ent.getKey();
    				String username = user.get("username").toString();
    				WebSocketServer.channels.remove(user);
    				for (Map.Entry<Object, Object> s : WebSocketServer.channels.entrySet()) {
    					Map<String, Object> maps = new HashMap<String, Object>();
    					maps.put("type", "logout");
    					maps.put("username", username);
    					Channel channel = (Channel) s.getValue();
    					channel.writeAndFlush(new TextWebSocketFrame(JSON.toJSONString(maps)));
    				}
    				break;
    			}
    		}
    		ctx.close();
    	}

源码下载地址：[https://download.csdn.net/download/qq\_37316272/10872047][https_download.csdn.net_download_qq_37316272_10872047]

netty权威指南下载地址：[https://download.csdn.net/download/qq\_37316272/10872031][https_download.csdn.net_download_qq_37316272_10872031]

欢迎大家下载，多多学习交流，我这个程序还有许多需要改进的地方，欢迎大家不吝赐教哦！

[https_download.csdn.net_download_qq_37316272_10872031]: https://download.csdn.net/download/qq_37316272/10872031
[https_blog.csdn.net_qq_37316272_article_details_85130365]: https://blog.csdn.net/qq_37316272/article/details/85130365
[https_download.csdn.net_download_qq_37316272_10872047]: https://download.csdn.net/download/qq_37316272/10872047