Netty 多用户聊天服务器实现

package org.example;

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

/**
 * 多用户聊天服务器
 */
public class MultiChatServer {
    private final int port;
    // 存储用户连接的 Map
    private final ConcurrentHashMap<String, ChannelHandlerContext> userMap = new ConcurrentHashMap<>();
    // 事件执行器组
    private final EventExecutorGroup group = new DefaultEventExecutorGroup(16);

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

    public void run() throws Exception {
        // 创建主线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        // 创建工作线程组
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            // 配置服务器启动参数
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            // 添加处理器到通道的pipeline中
                            ch.pipeline().addLast(new StringDecoder(), new StringEncoder(), new MultiChatServerHandler(userMap, group));
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);

            // 绑定端口并启动服务器
            ChannelFuture f = b.bind(port).sync();
            // 等待服务器关闭
            f.channel().closeFuture().sync();
        } finally {
            // 关闭工作线程组
            workerGroup.shutdownGracefully();
            // 关闭主线程组
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        // 创建服务器实例并运行
        new MultiChatServer(port).run();
    }
}