Java NIO 新 IO 与传统 IO 有何不同

发布时间:2025-02-11 20:12:11 作者:小樊
来源:亿速云 阅读:93

Java NIO(New IO)与传统IO(也称为阻塞式IO或BIO,Blocking IO)之间存在几个关键的区别:

1. 阻塞与非阻塞

2. 面向流与面向缓冲

3. 选择器(Selector)

4. 性能

5. 适用场景

示例代码

传统IO(BIO)

import java.io.*;
import java.net.*;

public class BIOServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8080);
        while (true) {
            Socket clientSocket = serverSocket.accept();
            new Thread(() -> {
                try (BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                     PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true)) {
                    String request;
                    while ((request = in.readLine()) != null) {
                        out.println("Echo: " + request);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

Java NIO(New IO)

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;
import java.util.*;

public class NIOServer {
    public static void main(String[] args) throws IOException {
        Selector selector = Selector.open();
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.bind(new InetSocketAddress(8080));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        while (true) {
            selector.select();
            Set<SelectionKey> selectedKeys = selector.selectedKeys();
            Iterator<SelectionKey> iter = selectedKeys.iterator();
            while (iter.hasNext()) {
                SelectionKey key = iter.next();

                if (key.isAcceptable()) {
                    handleAccept(key, selector);
                } else if (key.isReadable()) {
                    handleRead(key);
                }

                iter.remove();
            }
        }
    }

    private static void handleAccept(SelectionKey key, Selector selector) throws IOException {
        ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
        SocketChannel clientChannel = serverSocketChannel.accept();
        clientChannel.configureBlocking(false);
        clientChannel.register(selector, SelectionKey.OP_READ);
    }

    private static void handleRead(SelectionKey key) throws IOException {
        SocketChannel clientChannel = (SocketChannel) key.channel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        int bytesRead = clientChannel.read(buffer);
        if (bytesRead > 0) {
            buffer.flip();
            byte[] data = new byte[buffer.remaining()];
            buffer.get(data);
            String request = new String(data).trim();
            System.out.println("Received: " + request);
            clientChannel.write(ByteBuffer.wrap(("Echo: " + request).getBytes()));
        } else if (bytesRead == -1) {
            clientChannel.close();
        }
    }
}

通过上述对比和示例代码,可以看出Java NIO在处理高并发I/O操作时具有显著的优势。

推荐阅读:
  1. 04.JavaIO流问题
  2. Java中网络IO编程的示例分析

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