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本文将使用Netty快速实现一个聊天室应用，该应用基于WebSocket协议，用户可以在浏览器内聊天。

实现过程很简单，就几步。

一、处理Http请求

package cn.md.netty.websocket.groupchat;

import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import io.netty.handler.ssl.SslHandler;
import io.netty.handler.stream.ChunkedNioFile;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.URISyntaxException;
import java.net.URL;

/**
 * * @Author: Martin
 * * @Date    2024/9/2 11:21
 * * @Description
 **/
public class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

    // websocket的请求地址
    private final String wsUri;

    // 页面文件的地址
    private static final File PAGE_FILE;


    static {
        URL location = HttpRequestHandler.class.getProtectionDomain()
                .getCodeSource().getLocation();
        String path = null;
        try {
            path = location.toURI() + "wsChatClient.html";
            path = path.contains("file:") ? path.substring(5):path;
            PAGE_FILE = new File("/Users/jack/Documents/TMP/wsChatClient.html");
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }


    /**
     * see {@link #SimpleChannelInboundHandler(boolean)} with {@code true} as boolean parameter.
     */
    public HttpRequestHandler(String wsUri) {
        this.wsUri = wsUri;
    }

    /**
     * Is called for each message of type {@link I}.
     *
     * @param ctx the {@link ChannelHandlerContext} which this {@link SimpleChannelInboundHandler}
     *            belongs to
     * @param msg the message to handle
     * @throws Exception is thrown if an error occurred
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        if (wsUri.equalsIgnoreCase(request.uri())) {
            // 交给下一个InboudHandler 处理
            ctx.fireChannelRead(request.retain());
            return;
        }

        if (HttpUtil.is100ContinueExpected(request)) {
            // 发送 100 continue
            send100Continue(ctx);
        }
        // 读取文件内容到字节数组
        byte[] fileContent;
        try (RandomAccessFile file = new RandomAccessFile(PAGE_FILE, "r")) {
            fileContent = new byte[(int) file.length()];
            file.readFully(fileContent);
        } catch (IOException e) {
            // 处理文件读取错误
            DefaultFullHttpResponse errorResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.INTERNAL_SERVER_ERROR);
            ctx.writeAndFlush(errorResponse);
            return;
        }

        DefaultFullHttpResponse resp = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
        resp.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/html; charset=UTF-8");

        boolean keepAlive = HttpUtil.isKeepAlive(request);
        if (keepAlive) {
            resp.headers().set(HttpHeaderNames.CONTENT_LENGTH, fileContent.length);
            resp.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
        }

        // 将文件内容设置为响应内容
        resp.content().writeBytes(fileContent);

        ChannelFuture channelFuture = ctx.writeAndFlush(resp);

        if (!keepAlive) {
            channelFuture.addListener(ChannelFutureListener.CLOSE);
        }
        channelFuture.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture channelFuture) throws Exception {
                System.out.println("response empty last content success !");
            }
        });
    }

    private void send100Continue(ChannelHandlerContext ctx) {
        DefaultFullHttpResponse resp = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE);
        ctx.writeAndFlush(resp);
    }


    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        Channel channel = ctx.channel();
        System.out.println("client " + channel.remoteAddress() + "异常");
        cause.printStackTrace();
        ctx.close();
    }
}

二、处理WebSocket帧

package cn.md.netty.websocket.groupchat;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.concurrent.GlobalEventExecutor;

/**
 * 处理Websocket帧
 * * @Author: Martin
 * * @Date    2024/9/2 13:21
 * * @Description
 **/
public class TextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {

    public static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);


    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channels.add(channel);
        // 广播
        channels.writeAndFlush(new TextWebSocketFrame("[server] - " + channel.remoteAddress() + "加入"));
        System.out.println(channel.remoteAddress() + "加入");
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channels.writeAndFlush(new TextWebSocketFrame("[server] - " + channel.remoteAddress() + "离开"));
        System.out.println(channel.remoteAddress() + "离开");
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        System.out.println(channel.remoteAddress() + "在线");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        System.out.println(channel.remoteAddress() + "掉线");
    }


    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        Channel channel = ctx.channel();
        System.out.println(channel.remoteAddress() + " 异常");
        cause.printStackTrace();
        ctx.close();
    }

    /**
     * Is called for each message of type {@link I}.
     *
     * @param ctx the {@link ChannelHandlerContext} which this {@link SimpleChannelInboundHandler}
     *            belongs to
     * @param msg the message to handle
     * @throws Exception is thrown if an error occurred
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
        System.out.println("收到消息：" + msg.text());
        Channel channel = ctx.channel();
        for (Channel ch : channels){
            if (channel != ch){
                ch.writeAndFlush(new TextWebSocketFrame(channel.remoteAddress() + ":" + msg.text()));
            }else {
                ch.writeAndFlush(new TextWebSocketFrame("[you]" + msg.text()));
            }
        }
    }

}

三、实现ChannelInitializer

package cn.md.netty.websocket.groupchat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
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.stream.ChunkedWriteHandler;

/**
 * * @Author: Martin
 * * @Date    2024/9/2 13:37
 * * @Description
 **/
public class WebSocketChatServerInitializer extends ChannelInitializer<SocketChannel> {

    /**
     * This method will be called once the {@link Channel} was registered. After the method returns this instance
     * will be removed from the {@link ChannelPipeline} of the {@link Channel}.
     *
     * @param ch the {@link Channel} which was registered.
     * @throws Exception is thrown if an error occurs. In that case it will be handled by
     *                   {@link #exceptionCaught(ChannelHandlerContext, Throwable)} which will by default close
     *                   the {@link Channel}.
     */
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {

        ch.pipeline()
                .addLast(new HttpServerCodec())
                .addLast(new HttpObjectAggregator(64 * 1024))
                .addLast(new ChunkedWriteHandler())
                .addLast(new HttpRequestHandler("/ws"))
                .addLast(new WebSocketServerProtocolHandler("/ws"))
                .addLast(new TextWebSocketFrameHandler());
    }
}

四、服务器启动程序

package cn.md.netty.websocket.groupchat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * * @Author: Martin
 * * @Date    2024/9/2 13:40
 * * @Description
 **/
public class WebSocketChatServer {

    private final int port;

    public WebSocketChatServer(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        new WebSocketChatServer(8088).run();
    }

    public void run() throws Exception {

        NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new WebSocketChatServerInitializer())
                    .option(ChannelOption.SO_BACKLOG,128)
                    .childOption(ChannelOption.SO_KEEPALIVE,true);

            ChannelFuture channelFuture = serverBootstrap.bind(port).sync();
            System.out.println("bind port success");
            channelFuture.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
            System.out.println("server stop");
        }


    }

}

五、编写客户端

编写html代码，我这里的页面地址是 /Users/jack/Documents/TMP/wsChatClient.html，你的需要修改HttpRequestHandler.java中的文件路径。代码如下：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>WebSocket Chat</title>
</head>
<body>


<script type="text/javascript">

    var socket;
    if (!window.WebSocket) {
        window.WebSocket = window.MozWebSocket;
    }

    if (window.WebSocket) {
        socket = new WebSocket("ws://localhost:8088/ws");
        socket.onmessage = function(event) {
            console.log("receive message:" + event.data)
            var ele = document.getElementById('respText');
            ele.value = ele.value + "\n" + event.data;
        };

        socket.onopen = function(event) {
            var ele = document.getElementById('respText');
            ele.value = "连接开启";
        }

        socket.onclose = function(event) {
            var ele = document.getElementById('respText');
            ele.value = ele.value + "连接被关闭";
        }

    } else {
        alert("Your browser does not support WebSocket!");
    }



    function sendMessage(message) {
        if (!window.WebSocket) {
            alert("Your browser does not support WebSocket!")
            return;
        }
        if (socket.readyState == WebSocket.OPEN) {
            socket.send(message);
            console.log("send message:" + message)
        } else {
            alert("The connection is not open.");
        }
    }


</script>


<form onsubmit="return false">
    <h3>WebSocket Chat</h3>

    <textarea name="" id= "respText" style="width: 500px;height: 300px"></textarea>
    <input type="text" name="message" style="width: 300px" value="Welcome to chat.marding.cn">
    <input type="button" value="发送" onclick="sendMessage(this.form.message.value)">
    </input>
</form>
</body>
</html>

六、测试

可以打开多个页面进行测试～～～

---

我是马丁，喜欢可以点赞+关注哦~ See you ~