不使用selector

package com.yimin.springdemovscode.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class NioDemo {

    // 保存客户端连接
    static final List<SocketChannel> channels = new ArrayList<>();

    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.configureBlocking(false);// 连接非阻塞
        serverSocketChannel.socket().bind(new InetSocketAddress(8080));
        while (true) {
            SocketChannel socketChannel = serverSocketChannel.accept();// 客户端
            if (socketChannel != null) {
                System.out.println("客户端连接" + socketChannel.getRemoteAddress());
                socketChannel.configureBlocking(false);// 读数据非阻塞
                channels.add(socketChannel);// 保存客户端连接
            }

            Iterator<SocketChannel> it = channels.iterator();
            while (it.hasNext()) {
                SocketChannel channel = it.next();
                ByteBuffer buf = ByteBuffer.allocate(16);
                int read = channel.read(buf);
                if (read == -1) { // 客户端关闭连接
                    it.remove();
                    channel.close();
                } else if (read > 0) {
                    System.out.println("read:" + read);
                    System.out.println("读取到客户端消息:" + new String(buf.array()));
                }

            }
        }
    }
}

使用selector

package com.yimin.springdemovscode.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;

/**
 * nio demo
 */
public class NioDemoWithSelector {

    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 服务端
        serverSocketChannel.configureBlocking(false);// 连接非阻塞
        serverSocketChannel.socket().bind(new InetSocketAddress(8080));

        Selector selector = Selector.open();// 多路复用器
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);// 注册连接事件

        // 由selector进行监听，避免空轮询
        while (true) {
            selector.select();// 阻塞，等待事件发生
            Iterator<SelectionKey> it = selector.selectedKeys().iterator();// 发生的事件集合
            while (it.hasNext()) {
                SelectionKey key = it.next();// 本次处理的事件
                it.remove();// 移除本次处理的事件，需要手动移除，避免重复处理
                switch (key.interestOps()) {
                    case SelectionKey.OP_ACCEPT: // 接受连接事件
                        ServerSocketChannel channel = (ServerSocketChannel) key.channel();// 获取发生事件的channel
                        SocketChannel socketChannel = channel.accept();// 接受客户端连接，不会阻塞了
                        socketChannel.configureBlocking(false);
                        socketChannel.register(selector, SelectionKey.OP_READ);// 客户端注册读事件
                        break;
                    case SelectionKey.OP_READ: // 读事件
                        SocketChannel sc = (SocketChannel) key.channel();
                        ByteBuffer buf = ByteBuffer.allocate(16);
                        int read = sc.read(buf);
                        if (read == -1) { // 客户端关闭连接
                            sc.close();
                            key.cancel(); // 不处理本次事件
                        } else if (read > 0) {
                            System.out.println("read:" + read);
                            System.out.println("读取到客户端消息:" + new String(buf.array()));
                        }
                        break;
                    default:
                        break;
                }
            }
        }

    }
}