Java实现NIO聊天室的示例代码(群聊+私聊)

 <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.18</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

package moremorechat_nio;

import lombok.extern.slf4j.Slf4j;

import java.io.*;


@Slf4j
public class Utils {
    
    public static Message decode(byte[] buf) throws IOException, ClassNotFoundException {
        ByteArrayInputStream bais = new ByteArrayInputStream(buf);
        ObjectInputStream ois = new ObjectInputStream(bais);
        return (Message) ois.readObject();
    }

    
    public static byte[] encode(Message message) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(message);
        oos.flush();
        return baos.toByteArray();
    }
}

package moremorechat_nio;

public final class FinalValue {
    
    public static final int MSG_SYSTEM = 0;
    
    public static final int MSG_GROUP = 1;
    
    public static final int MSG_PRIVATE = 2;
    
    public static final int MSG_ONLINE = 3;
    
    public static final int MSG_NAME = 4;
}

package moremorechat_nio;

import java.io.Serializable;


public class Message implements Serializable {
    public int type;
    public String message;

    public Message() {
    }

    public Message(String message) {
        this.message = message;
    }

    public Message(int type, String message) {
        this.type = type;
        this.message = message;
    }

    @Override
    public String toString() {
        return "Message{" +
                "type=" + type +
                ", message='" + message + '\'' +
                '}';
    }
}

package moremorechat_nio;

import lombok.extern.slf4j.Slf4j;

import java.io.*;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Collectors;

import static moremorechat_nio.FinalValue.*;


@Slf4j
public class NioServer {
    private Selector selector;
    private ServerSocketChannel ssc;

    public NioServer() {
        try {
            // 创建 selector, 管理多个 channel
            selector = Selector.open();
            //打开ServerSocketChannel，用于监听客户端的连接，它是所有客户端连接的父通道
            ssc = ServerSocketChannel.open();
            ssc.bind(new InetSocketAddress(8888));
            //设置连接为非堵塞模式
            ssc.configureBlocking(false);
            // 2. 建立 selector 和 channel 的联系（注册）
            // SelectionKey 就是将来事件发生后，通过它可以知道事件和哪个channel的事件
            //将ServerSocketChannel注册到Reactor线程的多路复用器Selector上，监听ACCEPT事件
            ssc.reGISter(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        NioServer server = new NioServer();
        log.debug("server启动完成，等待用户连接...");
        try {
            server.listen();
        } catch (Exception e) {
            log.debug("发生了一些问题");
        }
    }

    
    private void listen() throws Exception {
        while (true) {
            // select 方法, 没有事件发生，线程阻塞，有事件，线程才会恢复运行, 通过Selector的select（）方法可以选择已经准备就绪的通道 （这些通道包含你感兴趣的的事件）
            //通过Selector的select（）方法可以选择已经准备就绪的通道 （这些通道包含你感兴趣的的事件）
            // select 在事件未处理时，它不会阻塞, 事件发生后要么处理，要么取消，不能置之不理
            selector.select();
            // 处理事件, selectedKeys 内部包含了所有发生的事件
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                // 处理key 时，要从 selectedKeys 集合中删除，否则下次处理就会有问题
                iterator.remove();
                // 区分事件类型
                if (key.isAcceptable()) {
                    ServerSocketChannel channel = (ServerSocketChannel) key.channel();
                    SocketChannel sc = channel.accept();
                    sc.configureBlocking(false);
                    sc.register(selector, SelectionKey.OP_READ);
                } else if (key.isReadable()) {
                    dealReadEvent(key);
                }
            }
        }
    }

    
    private void dealReadEvent(SelectionKey key) {
        SocketChannel channel = null;
        try {
            channel = (SocketChannel) key.channel();
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            int read = channel.read(buffer);
            // 如果是正常断开，read 的方法的返回值是 -1
            if (read == -1) {
                //cancel 会取消注册在 selector 上的 channel，并从 keys 集合中删除 key 后续不会再监听事件
                key.cancel();
            } else {
                buffer.flip();
                Message msg = Utils.decode(buffer.array());
                log.debug(msg.toString());
                dealMessage(msg, key, channel);
            }
        } catch (IOException | ClassNotFoundException e) {
            System.out.println((key.attachment() == null ? "匿名用户" : key.attachment()) + " 离线了..");
            dealMessage(new Message(MSG_SYSTEM, key.attachment() + " 离线了.."), key, channel);
            //取消注册
            key.cancel();
            //关闭通道
            try {
                channel.close();
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
        }
    }

    
    private void dealMessage(Message msg, SelectionKey key, SocketChannel channel) {
        switch (msg.type) {
            case MSG_NAME:
                key.attach(msg.message);
                log.debug("用户{}已上线", msg.message);
                getConnectedChannel(channel).forEach(selectionKey -> {
                    SocketChannel sc = (SocketChannel) selectionKey.channel();
                    sendMsgToClient(new Message("收到一条系统消息: " + msg.message + "已上线"), sc);
                });
                break;
            case MSG_GROUP:
                getConnectedChannel(channel).forEach(selectionKey -> {
                    SocketChannel sc = (SocketChannel) selectionKey.channel();
                    sendMsgToClient(new Message(key.attachment() + "给大家发送了一条消息: " + msg.message), sc);
                });
                break;
            case MSG_PRIVATE:
                String[] s = msg.message.split("_");
                AtomicBoolean flag = new AtomicBoolean(false);
                getConnectedChannel(channel).stream().filter(sk -> s[0].equals(sk.attachment())).forEach(selectionKey -> {
                    SocketChannel sc = (SocketChannel) selectionKey.channel();
                    sendMsgToClient(new Message(key.attachment() + "给你发送了一条消息: " + s[1]), sc);
                    flag.set(true);
                });
                if (!flag.get()){
                    sendMsgToClient(new Message(s[1]+"用户不存在,请重新输入！！！"), channel);
                }

                break;
            case MSG_ONLINE:
                ArrayList<String> onlineList = new ArrayList<>();
                onlineList.add((String) key.attachment());
                getConnectedChannel(channel).forEach(selectionKey -> onlineList.add((String) selectionKey.attachment()));
                sendMsgToClient(new Message(onlineList.toString()), channel);
                break;
            case MSG_SYSTEM:
                getConnectedChannel(channel).forEach(selectionKey -> {
                    SocketChannel sc = (SocketChannel) selectionKey.channel();
                    sendMsgToClient(new Message("收到一条系统消息: " + msg.message), sc);
                });
                break;
            default:
                break;
        }
    }

    
    private void sendMsgToClient(Message msg, SocketChannel sc) {
        try {
            byte[] bytes = Utils.encode(msg);
            sc.write(ByteBuffer.wrap(bytes));
        } catch (IOException e) {
            log.debug("sendMsgToClient出现了一些问题");
        }
    }

    
    private Set<SelectionKey> getConnectedChannel(SocketChannel channel) {
        return selector.keys().stream()
                .filter(item -> item.channel() instanceof SocketChannel && item.channel().isOpen() && item.channel() != channel)
                .collect(Collectors.toSet());
    }
}

package moremorechat_nio;

import lombok.extern.slf4j.Slf4j;

import java.io.*;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Scanner;

import static moremorechat_nio.FinalValue.*;


@Slf4j
public class NioClient {
    private Selector selector;
    private SocketChannel socketChannel;
    private String username;
    private static Scanner input;

    public NioClient() throws IOException {
        selector = Selector.open();
        socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 8888));
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ);
        log.debug("client启动完成......");
        log.debug("请输入你的名字完成注册");
        input = new Scanner(System.in);
        username = input.next();
        log.debug("欢迎{}来到聊天系统", username);
    }

    public static void main(String[] args) throws IOException {
        System.out.println("tips: \n1. 直接发送消息会发给当前的所有用户 \n2. @用户名:消息  会私发给你要发送的用户 \n3. 输入  查询在线用户  会显示当前的在线用户");
        NioClient client = new NioClient();

        //启动一个子线程接受服务器发送过来的消息
        new Thread(() -> {
            try {
                client.acceptMessageFromServer();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }, "receiveClientThread").start();

        //调用sendMessageToServer,发送消息到服务端
        client.sendMessageToServer();
    }

    
    private void sendMessageToServer() throws IOException {
        //先把用户名发给客户端
        Message message = new Message(MSG_NAME, username);
        byte[] bytes = Utils.encode(message);

        socketChannel.write(ByteBuffer.wrap(bytes));
        while (input.hasNextLine()) {
            String msgStr = input.next();

            Message msg;
            boolean isPrivate = msgStr.startsWith("@");
            if (isPrivate) {
                int idx = msgStr.indexOf(":");
                String targetName = msgStr.substring(1, idx);
                msgStr = msgStr.substring(idx + 1);
                msg = new Message(MSG_PRIVATE, targetName + "_" + msgStr);
            } else if ("查询在线用户".equals(msgStr)) {
                msg = new Message(MSG_ONLINE, "请求在线人数");
            } else {
                msg = new Message(MSG_GROUP, msgStr);
            }

            byte[] bytes1 = Utils.encode(msg);
            socketChannel.write(ByteBuffer.wrap(bytes1));
        }
    }

    
    private void acceptMessageFromServer() throws Exception {
        while (selector.select() > 0) {
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                iterator.remove();
                if (key.isReadable()) {
                    SocketChannel sc = (SocketChannel) key.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    sc.read(buffer);
                    Message message = Utils.decode(buffer.array());
                    log.debug(String.valueOf(message.message));
                }
            }
        }
    }
}