使用Java NIO编写高性能的服务器

从JDK 1.4开始，Java的标准库中就包含了NIO，即所谓的“New IO”。其中最重要的功能就是提供了“非阻塞”的IO，当然包括了Socket。NonBlocking的IO就是对select(Unix平台下)以及 WaitForMultipleObjects(Windows平台)的封装，提供了高性能、易伸缩的服务架构。

Server:

/**
 * 
 */
package nio.file;

import java.io.FileInputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Iterator;

/**
 * @author ztz
 *
 */
public class NIOServer {
	
	static int BLOCK=4096;
	//处理与客户端的交互
	public class HandleClient{
		protected FileChannel channel;
		protected ByteBuffer buffer;
		public HandleClient() throws IOException{
			this.channel = new FileInputStream(filename).getChannel();
			this.buffer = ByteBuffer.allocate(BLOCK);
		}
		public ByteBuffer readBlock(){
			try {
				buffer.clear();
				int count = channel.read(buffer);
				buffer.flip();
				if(count<=0)
					return null;
			} catch (IOException e) {
				e.printStackTrace();
			}
			return buffer;
		}
		public void close(){
			try {
				channel.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	
	protected Selector selector;
	protected String filename = "XXX";
	protected ByteBuffer clientBuffer = ByteBuffer.allocate(BLOCK);
	protected CharsetDecoder decoder;
	public NIOServer(int port) throws IOException{
		selector = this.getSelector(port);
		Charset charset = Charset.forName("GB2312");
		decoder = charset.newDecoder();
	}
	//获取Selector
	protected Selector getSelector(int port) throws IOException{
		ServerSocketChannel server = ServerSocketChannel.open();
		Selector sel = Selector.open();
		server.socket().bind(new InetSocketAddress(port));
		server.configureBlocking(false);
		server.register(sel, SelectionKey.OP_ACCEPT);
		return sel;
	}
	//监听端口
	public void listen(){
			try {
				for(;;){
				selector.select();
				Iterator iter = selector.selectedKeys().iterator();
				while(iter.hasNext()){
					SelectionKey key = (SelectionKey) iter.next();
					iter.remove();
					handleKey(key);
				}
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			
	}
	//处理事件
	protected void handleKey(SelectionKey key) throws IOException {
		if(key.isAcceptable())//接收请求
		{
			ServerSocketChannel server = (ServerSocketChannel) key.channel();
			SocketChannel channel = server.accept();
			channel.configureBlocking(false);
			channel.register(selector, SelectionKey.OP_READ);
		}else if(key.isReadable())//读信息
		{
			SocketChannel channel = (SocketChannel) key.channel();
			int count = channel.read(clientBuffer);
			if(count>0){
				clientBuffer.flip();
				CharBuffer charBuffer = decoder.decode(clientBuffer);
				System.out.println("Client>>"+charBuffer.toString());
				SelectionKey wkey = channel.register(selector, SelectionKey.OP_WRITE);
				wkey.attach(new HandleClient());
			}else{
				channel.close();
				clientBuffer.clear();
			}
		}else if(key.isWritable())//写事件
		{
			SocketChannel channel = (SocketChannel) key.channel();
			HandleClient handle = (HandleClient) key.attachment();
			ByteBuffer block = handle.readBlock();
			if(block!=null){
				channel.write(block);
			}else{
				handle.close();
				channel.close();
			}
		}
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		try {
			int port = 12345;
			NIOServer server = new NIOServer(port);
			System.out.println("Listening on "+port);
			while(true){
				server.listen();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}

}

Client:

/**
 * 
 */
package nio.file;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.util.Iterator;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 文件下载客户端
 * @author ztz
 *
 */
public class NIOClient {
	
	static int SIZE = 100;
	static InetSocketAddress ip = new InetSocketAddress("localhost",12345);
	static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder();
	static class DownLoad implements Runnable{
		
		int index;
		public DownLoad(int index){
			this.index = index;
		}
		@Override
		public void run() {
			try {
				long start = System.currentTimeMillis();
				SocketChannel client = SocketChannel.open();
				client.configureBlocking(false);
				Selector selector = Selector.open();
				client.register(selector, SelectionKey.OP_CONNECT);
				client.connect(ip);
				ByteBuffer buffer = ByteBuffer.allocate(8*1024);
				int total = 0;
				FOR: for(;;){
					selector.select();
					Iterator iter = selector.selectedKeys().iterator();
					while(iter.hasNext()){
						SelectionKey key = (SelectionKey) iter.next();
						iter.remove();
						if(key.isConnectable()){
							SocketChannel channel = (SocketChannel) key.channel();
							if(channel.isConnectionPending()){
								channel.finishConnect();
								channel.write(encoder.encode(CharBuffer.wrap("Hello from "+index)));
								channel.register(selector, SelectionKey.OP_READ);
								
							}
						}else if (key.isReadable()){
							SocketChannel channel = (SocketChannel) key.channel();
							int count = channel.read(buffer);
							if(count > 0){
								total += count;
								buffer.clear();
							}else{
								client.close();
								break FOR;
							}
						}
					}
					
					double last = (System.currentTimeMillis()-start)*1.0/1000;
					System.out.println("Thread"+index+" download "+total+" bytes in "+last+"s.");
					
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ExecutorService exec = Executors.newFixedThreadPool(SIZE);
		for(int index = 0;index < SIZE;index++){
			exec.execute(new DownLoad(index));
		}
		exec.shutdown();
	}

}