• 日期: 2026-06-22
  • 标签: 常规

基于Netty的Java多人聊天室实现

本篇博客将详细介绍如何使用Netty构建一个基于Java的多人聊天室。我们将涵盖服务器端和客户端的实现，以及用户登录、聊天室列表、消息发送和私聊功能。

一、服务器端实现

1. 服务器端主类 MultiChatServerjavaimport io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;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.string.StringDecoder;import io.netty.handler.codec.string.StringEncoder;import io.netty.util.concurrent.DefaultEventExecutorGroup;import io.netty.util.concurrent.EventExecutorGroup;

import java.util.concurrent.ConcurrentHashMap;

public class MultiChatServer { private final int port; private final ConcurrentHashMap<String, ChannelHandlerContext> userMap = new ConcurrentHashMap<>(); private final EventExecutorGroup group = new DefaultEventExecutorGroup(16);

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

public void run() throws Exception {        EventLoopGroup bossGroup = new NioEventLoopGroup();        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            ServerBootstrap b = new ServerBootstrap();            b.group(bossGroup, workerGroup)                    .channel(NioServerSocketChannel.class)                    .childHandler(new ChannelInitializer<SocketChannel>() {                        @Override                        public void initChannel(SocketChannel ch) throws Exception {                            ch.pipeline().addLast(new StringDecoder(), new StringEncoder(), new MultiChatServerHandler(userMap, group));                        }                    })                    .option(ChannelOption.SO_BACKLOG, 128)                    .childOption(ChannelOption.SO_KEEPALIVE, true);

        ChannelFuture f = b.bind(port).sync();            f.channel().closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();            bossGroup.shutdownGracefully();        }    }

public static void main(String[] args) throws Exception {        int port = 8080;        if (args.length > 0) {            port = Integer.parseInt(args[0]);        }        new MultiChatServer(port).run();    }}

该类负责启动服务器并监听指定端口的连接请求。

  • 使用 NioEventLoopGroup 创建两个线程池，分别用于处理连接请求和处理IO事件。- 使用 ServerBootstrap 配置服务器，包括线程池、通道类型、处理器等。- 在 ChannelInitializer 中添加 StringDecoder 和 StringEncoder 用于字符串编解码，以及 MultiChatServerHandler 用于处理业务逻辑。

2. 消息处理器 MultiChatServerHandlerjavaimport io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;import io.netty.util.concurrent.EventExecutorGroup;

import java.util.Map;import java.util.concurrent.ConcurrentHashMap;

public class MultiChatServerHandler extends SimpleChannelInboundHandler { private final ConcurrentHashMap<String, ChannelHandlerContext> userMap; private final EventExecutorGroup group;

public MultiChatServerHandler(ConcurrentHashMap<String, ChannelHandlerContext> userMap, EventExecutorGroup group) {        this.userMap = userMap;        this.group = group;    }

@Override    public void channelActive(ChannelHandlerContext ctx) throws Exception {        System.out.println('Client connected: ' + ctx.channel().remoteAddress());    }

@Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception {        System.out.println('Client disconnected: ' + ctx.channel().remoteAddress());        userMap.values().remove(ctx);    }

@Override    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {        String[] tokens = msg.split('\|');        String command = tokens[0];

    switch (command) {            case 'LOGIN':                handleLogin(ctx, tokens[1], tokens[2]);                break;            case 'LIST':                handleList(ctx);                break;            case 'MSG':                handleMessage(ctx, tokens[1], tokens[2]);                break;            case 'PRIVATE':                handlePrivateMessage(ctx, tokens[1], tokens[2]);                break;            default:                ctx.writeAndFlush('Invalid command: ' + command);                break;        }    }

private void handleLogin(ChannelHandlerContext ctx, String username, String password) {        if (userMap.containsKey(username)) {            ctx.writeAndFlush('User already logged in: ' + username);        } else {            userMap.put(username, ctx);            ctx.writeAndFlush('Login successful: ' + username);        }    }

private void handleList(ChannelHandlerContext ctx) {        StringBuilder sb = new StringBuilder();        sb.append('Available users:

'); for (Map.Entry<String, ChannelHandlerContext> entry : userMap.entrySet()) { sb.append(entry.getKey()).append(' '); } ctx.writeAndFlush(sb.toString()); }

private void handleMessage(ChannelHandlerContext ctx, String recipient, String message) {        group.execute(() -> {            StringBuilder sb = new StringBuilder();            sb.append('[').append(ctx.channel().remoteAddress()).append('] ').append(message).append('

'); if (userMap.containsKey(recipient)) { userMap.get(recipient).writeAndFlush(sb.toString()); } else { ctx.writeAndFlush('User not found: ' + recipient); } }); }

private void handlePrivateMessage(ChannelHandlerContext ctx, String recipient, String message) {        handleMessage(ctx, recipient, message); // 私聊和群聊逻辑相同，只是recipient不同    }

@Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {        cause.printStackTrace();        ctx.close();    }}

该类负责处理客户端发送的各种消息，包括登录、获取聊天室列表、发送消息和发送私聊消息。

  • channelRead0 方法接收客户端发送的字符串消息，并根据消息类型进行处理。- handleLogin 方法处理用户登录请求，将用户名和对应的 ChannelHandlerContext 存入 userMap 中。- handleList 方法向客户端发送当前在线用户的列表。- handleMessage 方法处理发送消息请求，将消息转发给指定的用户。- handlePrivateMessage 方法处理发送私聊消息请求，与发送消息逻辑相同，只是接收方不同。

二、客户端实现

1. 客户端主类 MultiChatClientjavaimport io.netty.bootstrap.Bootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.EventLoopGroup;import io.netty.channel.nio.NioEventLoopGroup;import io.netty.channel.socket.SocketChannel;import io.netty.channel.socket.nio.NioSocketChannel;import io.netty.handler.codec.string.StringDecoder;import io.netty.handler.codec.string.StringEncoder;

import java.io.BufferedReader;import java.io.InputStreamReader;

public class MultiChatClient { private final String host; private final int port; private ChannelHandlerContext ctx;

public MultiChatClient(String host, int port) {        this.host = host;        this.port = port;    }

public void run() throws Exception {        EventLoopGroup group = new NioEventLoopGroup();        try {            Bootstrap b = new Bootstrap();            b.group(group)                    .channel(NioSocketChannel.class)                    .option(ChannelOption.SO_KEEPALIVE, true)                    .handler(new ChannelInitializer<SocketChannel>() {                        @Override                        public void initChannel(SocketChannel ch) throws Exception {                            ch.pipeline().addLast(new StringDecoder(), new StringEncoder(), new MultiChatClientHandler());                        }                    });

        ChannelFuture f = b.connect(host, port).sync();            ctx = f.channel().pipeline().context(MultiChatClientHandler.class);            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));            while (true) {                String line = in.readLine();                if (line == null) {                    break;                }                ctx.writeAndFlush(line + '

'); } } finally { group.shutdownGracefully(); } }

public static void main(String[] args) throws Exception {        String host = 'localhost';        int port = 8080;        if (args.length > 0) {            host = args[0];        }        if (args.length > 1) {            port = Integer.parseInt(args[1]);        }        new MultiChatClient(host, port).run();    }}

该类负责连接服务器并发送消息。

  • 使用 NioEventLoopGroup 创建线程池。- 使用 Bootstrap 配置客户端，包括线程池、通道类型、处理器等。- 在 ChannelInitializer 中添加 StringDecoder 和 StringEncoder 用于字符串编解码，以及 MultiChatClientHandler 用于处理业务逻辑。- 连接服务器后，从控制台读取用户输入并发送到服务器。

2. 消息处理器 MultiChatClientHandlerjavaimport io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;

public class MultiChatClientHandler extends SimpleChannelInboundHandler { @Override protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception { System.out.println(msg); }

@Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {        cause.printStackTrace();        ctx.close();    }}

该类负责接收服务器端的消息并打印到控制台。

三、使用方法

  1. 编译并运行 MultiChatServer 类启动服务器。2. 编译并运行多个 MultiChatClient 类启动客户端。3. 在客户端输入以下指令进行操作： - 登录：LOGIN|username|password - 查看在线用户列表：LIST - 发送消息：MSG|recipient|message - 发送私聊消息：PRIVATE|recipient|message

四、总结

本篇博客介绍了如何使用Netty构建一个基于Java的多人聊天室，包括服务器端和客户端的实现，以及用户登录、聊天室列表、消息发送和私聊功能。你可以根据自己的需要修改代码，添加更多功能。


原文地址: http://www.cveoy.top/t/topic/f1ZZ 著作权归作者所有。请勿转载和采集!

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