java手写解析换行符的NIO服务端

import com.google.common.base.Charsets;

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;
import java.util.Set;

class Scratch {

    public static void main(String[] args) {
        try {
            Selector selector = Selector.open();
            ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.bind(new InetSocketAddress("0.0.0.0", 8888));
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            while (true) {
                try {
                    if (selector.select() > 0) {
                        Set<SelectionKey> keySet = selector.selectedKeys();
                        Iterator<SelectionKey> iterator = keySet.iterator();
                        while (iterator.hasNext()) {
                            SelectionKey selectionKey = iterator.next();
                            iterator.remove();
                            if (selectionKey.isValid()) {
                                if (selectionKey.isAcceptable()) {
                                    ServerSocketChannel serverSocketChannel1 = ((ServerSocketChannel) selectionKey.channel());
                                    SocketChannel socketChannel = serverSocketChannel1.accept();
                                    socketChannel.configureBlocking(false);
                                    socketChannel.register(selector, SelectionKey.OP_READ)
                                            //附加连接属性对象
                                            .attach(ByteBuffer.allocate(1024));
                                }
                                if (selectionKey.isReadable()) {
                                    lineBasedLimiterCodec(selectionKey);
                                }
                            }
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    static void lineBasedLimiterCodec(SelectionKey selectionKey) throws Exception {
        ByteBuffer dataBuf = ((ByteBuffer) selectionKey.attachment());
        SocketChannel socketChannel = ((SocketChannel) selectionKey.channel());
        ByteBuffer byteBuffer = ByteBuffer.allocate(1);
        int length = socketChannel.read(byteBuffer);
        //连接断开
        if (length < 0) {
            socketChannel.close();
        } else {
            byte[] data = new byte[length];
            byteBuffer.flip();
            byteBuffer.get(data);
            int char_ = data[0];
            //监听回车符
            if (char_ != '\r') {
                dataBuf.put(data);
            } else {
                int realLength = dataBuf.position();
                byte[] data_ = new byte[realLength];
                dataBuf.flip();
                //去掉换行符
                if (dataBuf.get() == '\n') {
                    dataBuf.position(1);
                    data_ = new byte[realLength - 1];
                } else {
                    dataBuf.position(0);
                }
                dataBuf.get(data_);
                String resp = new String(data_, Charsets.UTF_8);
                System.err.println("read msg=" + resp);
                socketChannel.write(ByteBuffer.wrap("hello client\r\n".getBytes()));
                dataBuf.clear();
            }
        }
    }
}