3.Netty之一个基于NIO的服务端

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本文介绍了一个基于 Java NIO 的服务端实现案例。通过创建 Selector 和 ServerSocketChannel 来处理客户端连接请求，并实现了非阻塞模式下的读写操作。

看了一下《Java NIO》这本书，然后尝试着写了一个服务端demo

package com.bj58.pn.nio;

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.util.Iterator;

public class NonIOServer implements Runnable {
	Selector selector;

	public NonIOServer(int port) throws IOException {
		// 0.开启selector监听器
		selector = Selector.open();
		// 1.开启通道
		ServerSocketChannel ssc = ServerSocketChannel.open();
		// 2.通道监听端口
		ssc.bind(new InetSocketAddress(port));
		// 3.设置通道属性(非阻塞)
		ssc.configureBlocking(Boolean.FALSE);
		// 4.注册到selector选择器
		ssc.register(selector, SelectionKey.OP_ACCEPT);
	}

	@Override
	public void run() {
		while (true) {
			try {
				// 1.开始监听
				selector.select();
				// 2.获取多路复用器选择的结果集
				Iterator<SelectionKey> it = selector.selectedKeys().iterator();
				while (it.hasNext()) {
					SelectionKey key = it.next();
					it.remove();
					if (key.isValid() && key.isAcceptable()) {
						doAccept(key);
					}
					if (key.isValid() && key.isReadable()) {
						doRead(key);
					}
					if (key.isValid() && key.isWritable()) {
						doWrite(key);
					}
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private void doAccept(SelectionKey key) {
		try {
			SocketChannel sc = ((ServerSocketChannel) key.channel()).accept();
			sc.configureBlocking(Boolean.FALSE);
			sc.register(selector, SelectionKey.OP_READ);
		} catch (IOException e) {
			System.out.println("accept 异常");
			e.printStackTrace();
		}

	}

	private void doRead(SelectionKey key) {
		SocketChannel sc = (SocketChannel) key.channel();
		ByteBuffer reqBuffer = ByteBuffer.allocate(2048);

		try {
			int i = sc.read(reqBuffer);
			if (i >= 0) {
				reqBuffer.flip();
				byte[] bytes = new byte[reqBuffer.remaining()];
				reqBuffer.get(bytes);
				System.out.println(new String(bytes));
				key.attach("res");
				key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
			} else {
				sc.close();
			}
		} catch (IOException e) {
			System.out.println("read 异常");
			try {
				sc.close();
				sc.socket().close();
			} catch (IOException e1) {
				e1.printStackTrace();
			}
		}
	}

	private void doWrite(SelectionKey key) {
		SocketChannel sc = (SocketChannel) key.channel();
		String handle = (String) key.attachment();// 取出read方法传递的信息。
		ByteBuffer retBuffer = ByteBuffer.wrap(handle.getBytes());

		try {
			sc.write(retBuffer);
			sc.close();
		} catch (IOException e) {
			System.out.println("write 异常");
			e.printStackTrace();
		}
	}

	public static void main(String[] args) throws IOException {
		System.out.println("正在启动服务...");
		new Thread(new NonIOServer(8000)).start();
	}

}