SocketChannel用Selector和ThreadPoolExecutor做服务端

可以使用`SocketChannel`结合`Selector`和`ThreadPool`来实现服务端。下面是一个简单的示例代码：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Server {
    private Selector selector;
    private ServerSocketChannel serverSocketChannel;
    private ExecutorService executorService;

    private static final int BUFFER_SIZE = 1024;

    public static void main(String[] args) throws IOException {
        Server server = new Server();
        server.start(8080);
    }

    public void start(int port) throws IOException {
        // 创建Selector
        selector = Selector.open();

        // 创建ServerSocketChannel并绑定端口
        serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(port));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        // 创建线程池
        executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

        // 事件循环
        while (true) {
            // 阻塞等待就绪的事件
            selector.select();

            // 获取就绪的SelectionKey集合
            Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
            while (keyIterator.hasNext()) {
                SelectionKey key = keyIterator.next();
                keyIterator.remove();

                // 处理事件
                if (key.isAcceptable()) {
                    handleAcceptable(key);
                } else if (key.isReadable()) {
                    handleReadable(key);
                }
            }
        }
    }

    private void handleAcceptable(SelectionKey key) throws IOException {
        ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
        SocketChannel clientChannel = serverChannel.accept();
        clientChannel.configureBlocking(false);
        clientChannel.register(selector, SelectionKey.OP_READ);

        System.out.println("New client connected: " + clientChannel.getRemoteAddress());
    }

    private void handleReadable(SelectionKey key) {
        SocketChannel clientChannel = (SocketChannel) key.channel();
        ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
        try {
            int bytesRead = clientChannel.read(buffer);
            if (bytesRead > 0) {
                buffer.flip();
                byte[] data = new byte[buffer.remaining()];
                buffer.get(data);
                String message = new String(data).trim();
                System.out.println("Received message from client: " + message);

                // 在线程池中处理业务逻辑
                executorService.execute(() -> {
                    // 业务逻辑处理代码
                    // ...
                    // 响应客户端
                    ByteBuffer responseBuffer = ByteBuffer.wrap("Response from server".getBytes());
                    try {
                        clientChannel.write(responseBuffer);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                });
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这个示例代码创建了一个基于`SocketChannel`的服务端，使用`Selector`来实现异步的事件处理，使用`ThreadPoolExecutor`来处理业务逻辑。客户端连接的接收和读取操作在`handleAcceptable`和`handleReadable`方法中处理。读取到客户端消息后，会将业务逻辑交给线程池处理，并响应客户端。你可以根据自己的需要在业务逻辑处理代码中添加具体的业务逻辑。