Java NIO编程示例
服务端：
package org.example;
import org.apache.commons.lang3.StringUtils;
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;
import java.nio.channels.spi.SelectorProvider;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class NIOServer {
static ExecutorService executorService = Executors.newFixedThreadPool(10);
public static void main(String[] args) {
try {
// 打开一个选择器
Selector selector = SelectorProvider.provider().openSelector();
// 打开一个服务器套接字通道
ServerSocketChannel serverChannel = ServerSocketChannel.open();
serverChannel.configureBlocking(false);
// 绑定到指定端口
serverChannel.socket().bind(new InetSocketAddress(8081));
// 将服务器通道注册到选择器上，并指定关注的事件为接收连接
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("服务器已启动，监听端口8081...");
while (true) {
// 选择器等待就绪的通道
selector.select();
// 获取就绪的选键集合
Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
// 检查选键的状态并进行相应的处理
if (key.isAcceptable()) {
handleAccept(key);
} else if (key.isReadable()) {
processMsg(key);
} else if (key.isWritable()) {
// 通常这里不会处理写就绪，因为写操作通常由应用逻辑触发
} else if (key.isConnectable()) {
// 这是客户端连接的情况，对于服务器来说通常不会遇到
}
}
}
} catch (IOException e) {
e.printStackTrace();
System.err.println("服务器发生异常，已关闭。");
} finally {
executorService.shutdown();
}
}
private static void handleAccept(SelectionKey key) throws IOException {
ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
SocketChannel clientChannel = serverChannel.accept();
clientChannel.configureBlocking(false);
// 注册到选择器并关注读事件
clientChannel.register(key.selector(), SelectionKey.OP_READ);
System.out.println("接受到新的客户端连接：" + clientChannel.getRemoteAddress());
}
private static void sendData(SocketChannel socketChannel, String message) {
ByteBuffer buffer = ByteBuffer.wrap(message.getBytes());
while (buffer.hasRemaining()) {
try {
socketChannel.write(buffer);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
public static void processMsg(SelectionKey key) {
SocketChannel clientChannel = (SocketChannel) key.channel();
ByteBuffer buffer = ByteBuffer.allocate(1024);
StringBuilder sb = new StringBuilder();
try {
while (true) {
int bytesRead = clientChannel.read(buffer);
if (bytesRead == -1) { // 客户端关闭连接
clientChannel.close();
break;
} else if (bytesRead == 0) { // 消息读取结束
break;
}
buffer.flip();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
sb.append(new String(bytes, StandardCharsets.UTF_8));
buffer.clear();
}
if (!clientChannel.isOpen()) return;
executorService.submit(() -> {
System.out.println("收到消息：" + sb);
sendData(clientChannel, StringUtils.repeat("a", 10000000));
});
} catch (Exception e) {
// 发生读错误，关闭连接并打印错误信息
System.err.println("读错误：" + e.getMessage());
try {
clientChannel.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
客户端：
package org.example;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
public class NIOClient {
public static void main(String[] args) {
// 服务器的地址和端口
String serverAddress = "localhost";
int serverPort = 8081;
try {
// 打开一个套接字通道
SocketChannel socketChannel = SocketChannel.open();
// 配置为非阻塞模式
socketChannel.configureBlocking(false);
// 尝试连接到服务器
if (socketChannel.connect(new InetSocketAddress(serverAddress, serverPort))) {
// 连接成功，可以直接发送数据（但在非阻塞模式下，这通常不会发生）
sendData(socketChannel, "Hello, Server!");
} else {
// 连接可能需要时间，等待连接完成（在实际应用中，这通常是在一个循环中完成的）
while (!socketChannel.finishConnect()) {
// 可以在这里执行其他任务，比如更新用户界面等
// 但在这个简单的例子中，我们只是空转等待连接完成
}
// 连接完成，发送数据
for (int index = 1; index <= 5; index++) {
sendData(socketChannel, "Hello, Server!");
}
}
// 读取服务器的响应（在非阻塞模式下，这可能需要多次尝试）
StringBuilder sb = new StringBuilder();
ByteBuffer buffer = ByteBuffer.allocate(1024);
while (socketChannel.read(buffer) <= 0) {
// 如果没有数据可读，可以在这里执行其他任务
// 但在这个简单的例子中，我们只是空转等待数据到来
}
// 服务器发送过来的所有数据
buffer.flip();
String response = new String(buffer.array(), 0, buffer.limit());
sb.append(response);
buffer.clear();
while (socketChannel.read(buffer) > 0) {
buffer.flip();
response = new String(buffer.array(), 0, buffer.limit());
sb.append(response);
buffer.clear();
}
System.out.println("Received from server: " + sb);
// 关闭连接
socketChannel.close();
} catch (Exception e) {
e.printStackTrace();
System.err.println("Client failed to connect to server or read response.");
}
System.out.println("finish");
}
private static void sendData(SocketChannel socketChannel, String message) throws Exception {
ByteBuffer buffer = ByteBuffer.wrap(message.getBytes());
while (buffer.hasRemaining()) {
socketChannel.write(buffer);
}
}
}
执行效果：
