JAVA NIO实现简单聊天室功能

在JAVA NIO（New IO）中，实现简单聊天室功能通常需要以下步骤：

1. 创建ServerSocketChannel/IoServerSocketChannel实例

在JAVA NIO中，ServerSocketChannel和IoServerSocketChannel类分别充当服务器端的套接字通道。需要通过这两个类的实例来处理客户端请求的连接。

示例代码：

ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.socket().bind(new InetSocketAddress("127.0.0.1",8080));

2. 创建Selector对象

Selector对象用来统一管理I/O事件的注册、删除以及处理等操作。

示例代码：

Selector selector = Selector.open();
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

3. 监听连接请求

在ServerSocketChannel/IoServerSocketChannel实例中调用accept()方法，通过Selector管理Accept操作。

示例代码：

while(true) {
    selector.select();
    Set<SelectionKey> selectionKeySet= selector.keys();
    for(SelectionKey selectionKey : selectionKeySet) {
        if(selectionKey.isAcceptable()) {
            SocketChannel channel = ((ServerSocketChannel)selectionKey.channel()).accept();
            channel.configureBlocking(false);
            channel.register(selector, SelectionKey.OP_READ);
        }
    }
}

4. 处理连接请求

在连接被建立成功之后，就需要处理请求发送的信息。客户端向服务器请求的是一个聊天室连接，所以需要实现数据的读取、转发、以及广播等功能。

示例代码：

while(true) {
    selector.select();
    Set<SelectionKey> selectionKeySet= selector.keys();
    for(SelectionKey selectionKey : selectionKeySet) {
        if(selectionKey.isAcceptable()) {
            SocketChannel channel = ((ServerSocketChannel)selectionKey.channel()).accept();
            channel.configureBlocking(false);
            channel.register(selector, SelectionKey.OP_READ);
        }else if(selectionKey.isReadable()) {
            SocketChannel channel = (SocketChannel) selectionKey.channel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            channel.read(byteBuffer);
            String message = new String(byteBuffer.array(), StandardCharsets.UTF_8);
            System.out.println("receive message:"+message);
            for(SelectionKey key : selectionKeySet) {
                Channel targetChannel = key.channel();
                if(targetChannel instanceof SocketChannel && targetChannel != channel) {
                    ((SocketChannel) targetChannel).write(ByteBuffer.wrap(message.getBytes(StandardCharsets.UTF_8)));
                }
            }
        }
    }
}

示例1：客户端发送信息并广播

public static void main(String[] args) throws IOException, InterruptedException {
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.connect(new InetSocketAddress("localhost", 8080));
        socketChannel.configureBlocking(false);
        while(!socketChannel.finishConnect() ){//自旋
        }
        Thread thread = new Thread(() -> {
            while(true) {
                ByteBuffer buf = ByteBuffer.allocate(1024);
                try {
                    socketChannel.read(buf);
                    buf.flip();
                    String data = new String(buf.array()).trim();
                    System.out.println("服务端回送的数据："+data);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        });
        Scanner scanner = new Scanner(System.in);
        thread.start();
        String line = "";
        while (!line.equals("quit")) {
            line = scanner.nextLine();
            ByteBuffer buffer = ByteBuffer.wrap(line.getBytes(StandardCharsets.UTF_8));
            socketChannel.write(buffer);
        }
        socketChannel.close();
    }

示例2：客户端接收来自服务端的广播信息

public static void main(String[] args) throws IOException {
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.connect(new InetSocketAddress("localhost", 8080));
        socketChannel.configureBlocking(false);
        while(!socketChannel.finishConnect() ){//自旋
        }

        ByteBuffer buf = ByteBuffer.allocate(1024);
        int count = 0;
        while((count = socketChannel.read(buf))>=0) {
            buf.flip();
            String message = new String(buf.array(),0,count,StandardCharsets.UTF_8);
            System.out.println("receive message:"+message);
        }
        socketChannel.close();
    }

以上就是JAVA NIO实现简单聊天室功能的完整攻略。