java非阻塞io案例

Java的非阻塞IO（Non-blocking I/O）通常通过I/O复用技术实现，比如Epoll、Kqueue（Unix系统）或Selector（Java NIO）。这种方式允许线程在等待I/O事件发生时不会阻塞，而是继续执行其他任务。

以下是一个简单的Java NIO非阻塞IO案例：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

public class NonBlockingServer {
    private Selector selector;
    private ServerSocketChannel server;

    public void start(int port) throws IOException {
        server = ServerSocketChannel.open();
        server.socket().bind(new InetSocketAddress(port));
        selector = Selector.open();
        server.register(selector, SelectionKey.OP_ACCEPT);
        while (true) {
            if (selector.selectNow() > 0) {
                for (SelectionKey key : selector.selectedKeys()) {
                    if (key.isAcceptable()) {
                        accept(key);
                    } else if (key.isReadable()) {
                        processRead(key);
                    }
                }
            }
        }
    }

    private void accept(SelectionKey key) {
        try (SocketChannel client = server.accept()) {
            client.configureBlocking(false);
            client.register(selector, SelectionKey.OP_READ);
        } catch (IOException e) {
            System.err.println("Error accepting connection: " + e.getMessage());
        }
    }

    private void processRead(SelectionKey key) {
        try (SocketChannel channel = (SocketChannel) key.channel()) {
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            int read = channel.read(buffer);
            if (read > 0) {
                buffer.flip();
                // handle the received data here
                System.out.println("Received: " + new String(buffer.array()));
                buffer.clear(); // reset buffer for next read
            } else if (read == -1) { // closed socket
                key.cancel();
            } else { // error reading
                key.close();
            }
        } catch (IOException e) {
            System.err.println("Error reading from client: " + e.getMessage());
        }
    }
}