nio示例

public class NioService {

private Selector selector;

public void init{
    try {
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);//开启非阻塞模式
        ssc.socket().bind(new InetSocketAddress(8082));//绑定监听端口
        selector = Selector.open();
        ssc.register(selector, SelectionKey.OP_ACCEPT);//注册选择器
        Handler handler = new Handler();
        while (true){
            if(selector.select(3000)==0){//使用超时方式完成非阻塞操作
                System.out.println("等待请求超时。。。。。。。。。");
                continue;
            }
            Iterator it = selector.selectedKeys().iterator();
            while (it.hasNext()){
                try {
                    SelectionKey sk = it.next();
                    if (sk.isAcceptable()) {//接收就绪
                        handler.handAccept(sk);
                    }
                    if (sk.isReadable()) {//读就绪
                        handler.handRead(sk);
                    }
                }catch (Exception e){
                    e.printStackTrace();
                }finally {
                    it.remove();//一定要手动去除完成的selectionKey，否则selector会一直保持它
                }
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private class Handler{
    //在接收准备好后，给准备好的SocketChannel注册读就绪选择器
    public void handAccept(SelectionKey key) throws IOException {
        SocketChannel socketChannel = ((ServerSocketChannel) key.channel()).accept();
        socketChannel.configureBlocking(false);//非阻塞
        socketChannel.register(selector,SelectionKey.OP_READ);
    }

//将上传的文件转存到本地文件夹
    public void handRead(SelectionKey key) throws IOException {
        SocketChannel socketChannel = null;
        FileChannel fileChannel = null;
        try {
            socketChannel = ((SocketChannel) key.channel());
            //准备ByteBuffer
            ByteBuffer byteBuffer = ByteBuffer.allocate(128);
            byteBuffer.clear();
            //准备目标channel
            File file = new File("file/");
            if(!file.exists()){
                file.mkdirs();
            }
            fileChannel = new FileOutputStream("file/"+UUID.randomUUID().toString()).getChannel();
            //转存
            while (socketChannel.read(byteBuffer) != -1) {
                byteBuffer.flip();
                fileChannel.write(byteBuffer);
                byteBuffer.clear();//一定要clear()
            }
            //下面不确定正确性
            byteBuffer.clear();
            String sendString = "ok";
            byteBuffer.put(sendString.getBytes("utf-8"));
            socketChannel.write(byteBuffer);
        }catch (IOException e){
            throw e;
        }finally {
            if(fileChannel!=null)
                fileChannel.close();
            if(socketChannel!=null)
                socketChannel.close();
        }
    }
}

}