彤哥说netty系列之Java NIO实现群聊（自己跟自己聊上瘾了）

// 这是一个内部类private static class ChatHolder {    // 我们只用了一个线程，用普通的HashMap也可以    static final Map<SocketChannel, String> USER_MAP = new ConcurrentHashMap<>();
    /**     * 加入群聊     * @param socketChannel     */    static void join(SocketChannel socketChannel) {        // 有人加入就给他分配一个id，本文来源于公从号“彤哥读源码”        String userId = "用户"+ ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);        send(socketChannel, "您的id为：" + userId + "\n\r");
        for (SocketChannel channel : USER_MAP.keySet()) {            send(channel, userId + " 加入了群聊" + "\n\r");        }
        // 将当前用户加入到map中        USER_MAP.put(socketChannel, userId);    }
    /**     * 退出群聊     * @param socketChannel     */    static void quit(SocketChannel socketChannel) {        String userId = USER_MAP.get(socketChannel);        send(socketChannel, "您退出了群聊" + "\n\r");        USER_MAP.remove(socketChannel);
        for (SocketChannel channel : USER_MAP.keySet()) {            if (channel != socketChannel) {                send(channel, userId + " 退出了群聊" + "\n\r");            }        }    }
    /**     * 扩散说话的内容     * @param socketChannel     * @param content     */    public static void propagate(SocketChannel socketChannel, String content) {        String userId = USER_MAP.get(socketChannel);        for (SocketChannel channel : USER_MAP.keySet()) {            if (channel != socketChannel) {                send(channel, userId + ": " + content + "\n\r");            }        }    }
    /**     * 发送消息     * @param socketChannel     * @param msg     */    static void send(SocketChannel socketChannel, String msg) {        try {            ByteBuffer writeBuffer = ByteBuffer.allocate(1024);            writeBuffer.put(msg.getBytes());            writeBuffer.flip();            socketChannel.write(writeBuffer);        } catch (Exception e) {            e.printStackTrace();        }    }}

public class ChatServer {    public static void main(String[] args) throws IOException {        Selector selector = Selector.open();        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();        serverSocketChannel.bind(new InetSocketAddress(8080));        serverSocketChannel.configureBlocking(false);        // 将accept事件绑定到selector上        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        while (true) {            // 阻塞在select上            selector.select();            Set<SelectionKey> selectionKeys = selector.selectedKeys();            // 遍历selectKeys            Iterator<SelectionKey> iterator = selectionKeys.iterator();            while (iterator.hasNext()) {                SelectionKey selectionKey = iterator.next();                // 如果是accept事件                if (selectionKey.isAcceptable()) {                    ServerSocketChannel ssc = (ServerSocketChannel) selectionKey.channel();                    SocketChannel socketChannel = ssc.accept();                    System.out.println("accept new conn: " + socketChannel.getRemoteAddress());                    socketChannel.configureBlocking(false);                    socketChannel.register(selector, SelectionKey.OP_READ);                    // 加入群聊，本文来源于公从号“彤哥读源码”                    ChatHolder.join(socketChannel);                } else if (selectionKey.isReadable()) {                    // 如果是读取事件                    SocketChannel socketChannel = (SocketChannel) selectionKey.channel();                    ByteBuffer buffer = ByteBuffer.allocate(1024);                    // 将数据读入到buffer中                    int length = socketChannel.read(buffer);                    if (length > 0) {                        buffer.flip();                        byte[] bytes = new byte[buffer.remaining()];                        // 将数据读入到byte数组中                        buffer.get(bytes);
                        // 换行符会跟着消息一起传过来                        String content = new String(bytes, "UTF-8").replace("\r\n", "");                        if (content.equalsIgnoreCase("quit")) {                            // 退出群聊，本文来源于公从号“彤哥读源码”                            ChatHolder.quit(socketChannel);                            selectionKey.cancel();                            socketChannel.close();                        } else {                            // 扩散，本文来源于公从号“彤哥读源码”                            ChatHolder.propagate(socketChannel, content);                        }                    }                }                iterator.remove();            }        }    }}