编辑“︁Java Selector”︁（章节）

== 基本用法 ==

以下是 Selector 的基本使用流程：

1. 创建 Selector。
2. 将通道注册到 Selector，并指定感兴趣的事件。
3. 循环调用 `select()` 方法等待事件。
4. 处理就绪的通道。

=== 代码示例 ===
<syntaxhighlight lang="java">
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
import java.util.Set;

public class SelectorExample {
    public static void main(String[] args) throws IOException {
        // 1. 创建 Selector
        Selector selector = Selector.open();

        // 2. 创建 ServerSocketChannel 并注册到 Selector
        ServerSocketChannel serverSocket = ServerSocketChannel.open();
        serverSocket.bind(new InetSocketAddress(8080));
        serverSocket.configureBlocking(false);
        serverSocket.register(selector, SelectionKey.OP_ACCEPT);

        System.out.println("Server started on port 8080");

        while (true) {
            // 3. 阻塞等待事件
            selector.select();

            // 4. 获取就绪的 SelectionKey 集合
            Set<SelectionKey> selectedKeys = selector.selectedKeys();
            Iterator<SelectionKey> iter = selectedKeys.iterator();

            while (iter.hasNext()) {
                SelectionKey key = iter.next();

                if (key.isAcceptable()) {
                    // 处理连接就绪事件
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel client = server.accept();
                    client.configureBlocking(false);
                    client.register(selector, SelectionKey.OP_READ);
                    System.out.println("Client connected: " + client.getRemoteAddress());
                } else if (key.isReadable()) {
                    // 处理读就绪事件
                    SocketChannel client = (SocketChannel) key.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    int bytesRead = client.read(buffer);
                    if (bytesRead == -1) {
                        client.close();
                        System.out.println("Client disconnected");
                    } else {
                        buffer.flip();
                        byte[] data = new byte[buffer.remaining()];
                        buffer.get(data);
                        System.out.println("Received: " + new String(data));
                    }
                }

                iter.remove();
            }
        }
    }
}
</syntaxhighlight>

=== 输出示例 ===
<pre>
Server started on port 8080
Client connected: /127.0.0.1:12345
Received: Hello, Selector!
Client disconnected
</pre>