Java的網(wǎng)絡(luò)編程有兩種主要的技術(shù)：Java NIO 和 Java Netty。

Java NIO即Java Non-blocking I/O， 可以實(shí)現(xiàn)同步和異步兩種IO操作。它提供了Channel、Buffer、Selector等實(shí)現(xiàn)，使得Java程序可以實(shí)現(xiàn)高效的I/O操作，避免阻塞等待發(fā)生。Java NIO的代碼量更少，效率更高。例如：

public class NIOServer {
	public static void main(String[] args) throws IOException {
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.socket().bind(new InetSocketAddress(9999));
serverSocketChannel.configureBlocking(false);
Selector selector = Selector.open();
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
while (true) {
if (selector.select(5000) == 0) {
System.out.println("5秒鐘內(nèi)沒有客戶端連接");
} else {
SetselectionKeys = selector.selectedKeys();
IteratorkeyIterator = selectionKeys.iterator();
while (keyIterator.hasNext()) {
SelectionKey selectionKey = keyIterator.next();
if (selectionKey.isAcceptable()) {
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(1024));
System.out.println("連接成功");
}
if (selectionKey.isReadable()) {
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
ByteBuffer byteBuffer = (ByteBuffer) selectionKey.attachment();
socketChannel.read(byteBuffer);
System.out.println(new String(byteBuffer.array()));
}
keyIterator.remove();
}
}
}
	}
}

Java Netty是一個(gè)異步的、事件驅(qū)動(dòng)的網(wǎng)絡(luò)應(yīng)用框架。它是網(wǎng)絡(luò)編程的高級(jí)模式，把網(wǎng)絡(luò)操作都抽象成一組事件，然后交由事件驅(qū)動(dòng)的程序處理。Netty更高級(jí)，使用更方便，它的API非常友好，可以使用多種設(shè)計(jì)模式和機(jī)制，方便地實(shí)現(xiàn)自定義協(xié)議。例如：

public class NettyServer {
	public static void main(String[] args) throws InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_BACKLOG, 1024)
.childOption(ChannelOption.SO_KEEPALIVE, true)
.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(new LineBasedFrameDecoder(1024));
p.addLast(new StringDecoder());
p.addLast(new ServerHandler());
}
});
ChannelFuture f = serverBootstrap.bind(9999).sync();
f.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
	}
}
public class ServerHandler extends ChannelInboundHandlerAdapter {
	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
String body = (String) msg;
System.out.println("客戶端發(fā)來的請(qǐng)求為：" + body);
String response = "hello client";
response += System.getProperty("line.separator");
ctx.writeAndFlush(response.getBytes());
	}
@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
	}
@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
System.err.println("發(fā)生異常：" + cause.getMessage());
	}
}

Java NIO和Java Netty都是Java網(wǎng)絡(luò)編程中不可缺少的部分，應(yīng)該針對(duì)實(shí)際應(yīng)用場景選擇合適的技術(shù)。