基于 Netty 框架的多人聊天室实现

本文将介绍使用 Netty 框架实现一个多人聊天室，包括用户登录、聊天室列表、消息发送和私聊功能。

服务器端代码实现

import 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;
        new MultiChatServer(port).run();
    }
}

MultiChatServerHandler 类实现了服务器端的消息处理逻辑，包括用户登录、聊天室列表、消息发送和私聊功能。具体实现如下：

import 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<String> {
    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 chat rooms:
');
        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('] (private) ').append(message).append('
');
        if (userMap.containsKey(recipient)) {
            userMap.get(recipient).writeAndFlush(sb.toString());
        } else {
            ctx.writeAndFlush('User not found: ' + recipient);
        }
    }

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

客户端代码实现

import 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;
        new MultiChatClient(host, port).run();
    }
}

MultiChatClientHandler 类实现了客户端的消息处理逻辑，包括接收服务器端的消息和向服务器端发送消息。具体实现如下：

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class MultiChatClientHandler extends SimpleChannelInboundHandler<String> {
    @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();
    }
}

运行示例

启动服务器端

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

启动客户端

public static void main(String[] args) throws Exception {
    String host = 'localhost';
    int port = 8080;
    new MultiChatClient(host, port).run();
}

客户端登录

LOGIN|username|password

查看聊天室列表

LIST

进入聊天室

MSG|roomName|message

私聊

PRIVATE|recipient|message

代码说明

服务器端使用 ConcurrentHashMap 来存储用户和其对应 ChannelHandlerContext 的映射关系，方便快速查找用户。
服务器端使用 EventExecutorGroup 来处理多个用户的连接和消息，提高并发性能。
客户端使用 BufferedReader 从控制台读取用户输入，并将输入发送到服务器。
客户端和服务器端都使用 StringDecoder 和 StringEncoder 来编码和解码字符串消息。

总结

本代码示例展示了使用 Netty 框架实现一个多人聊天室的基本步骤，用户可以根据自身需求进行扩展和完善。

该代码完整，并实现了用户登录、聊天室列表、消息发送和私聊功能。运行示例中，用户可以使用不同的命令进行操作，并与其他用户进行聊天。