使用Netty构建Java多人聊天室：完整指南

概述

本指南将引导您使用Netty库构建一个简单的Java多人聊天室应用程序。本教程将涵盖服务器端和客户端，并提供有关如何编译、打包和运行应用程序的分步说明。

代码

1. 服务器端 (MultiChatServer.java)javaimport 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();            System.out.println('服务器启动，监听端口：' + port);            f.channel().closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();            bossGroup.shutdownGracefully();        }    }

public static void main(String[] args) throws Exception {        int port = 8080;        new MultiChatServer(port).run();    }}

2. 服务器消息处理器 (MultiChatServerHandler.java)javaimport 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('客户端连接：' + ctx.channel().remoteAddress());    }

@Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception {        System.out.println('客户端断开连接：' + 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('无效的命令：' + command);                break;        }    }

private void handleLogin(ChannelHandlerContext ctx, String username, String password) {        if (userMap.containsKey(username)) {            ctx.writeAndFlush('用户已登录：' + username);        } else {            userMap.put(username, ctx);            ctx.writeAndFlush('登录成功：' + username);        }    }

private void handleList(ChannelHandlerContext ctx) {        StringBuilder sb = new StringBuilder();        sb.append('在线用户：

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

private void handleMessage(ChannelHandlerContext ctx, String roomName, String message) {        StringBuilder sb = new StringBuilder();        sb.append('[').append(ctx.channel().remoteAddress()).append('] ').append(message).append('

'); for (Map.Entry<String, ChannelHandlerContext> entry : userMap.entrySet()) { if (entry.getKey().equals(roomName)) { entry.getValue().writeAndFlush(sb.toString()); } } }

private void handlePrivateMessage(ChannelHandlerContext ctx, String recipient, String message) {        StringBuilder sb = new StringBuilder();        sb.append('[').append(ctx.channel().remoteAddress()).append('] (私聊) ').append(message).append('

'); if (userMap.containsKey(recipient)) { userMap.get(recipient).writeAndFlush(sb.toString()); } else { ctx.writeAndFlush('用户未找到：' + recipient); } }

@Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {        cause.printStackTrace();        ctx.close();    }}### 3. 客户端 (MultiChatClient.java)javaimport 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(MultiChatClient.this));                        }                    });

        ChannelFuture f = b.connect(host, port).sync();            ctx = f.channel().pipeline().context(MultiChatClientHandler.class);            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));            System.out.println('连接成功！请输入消息：');            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;        new MultiChatClient(host, port).run();    }

public void setCtx(ChannelHandlerContext ctx) {        this.ctx = ctx;    }}

4. 客户端消息处理器 (MultiChatClientHandler.java)javaimport io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;

public class MultiChatClientHandler extends SimpleChannelInboundHandler { private MultiChatClient client; public MultiChatClientHandler(MultiChatClient client){ this.client = client; } @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();    }

@Override    public void channelActive(ChannelHandlerContext ctx) throws Exception {        client.setCtx(ctx);