10.处理write写事件

@Slf4j
public class NioServer {

    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.configureBlocking(false);
        Selector selector = Selector.open();
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        serverSocketChannel.bind(new InetSocketAddress(8000));
        while (true) {
            selector.select();
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            if(iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();
                iterator.remove();
                //与客户端建立连接
                if(selectionKey.isAcceptable()) {
                    //因为ServerSocketChannel只有一个，可以直接使用
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    socketChannel.configureBlocking(false);
                    SelectionKey acceptKey = socketChannel.register(selector, 0, null);
                    acceptKey.interestOps(SelectionKey.OP_READ);

                    //向客户端发大量数据
                    StringBuilder sb = new StringBuilder();
                    for (int i = 0; i < 5000000; i++) {
                        sb.append("a");
                    }
                    ByteBuffer byteBuffer = StandardCharsets.UTF_8.encode(sb.toString());

                    //返回实际写的字节数
                    int write = socketChannel.write(byteBuffer);
                    log.info("write1={}", write);
                    if(byteBuffer.hasRemaining()) {
                        //添加关注写事件
                        acceptKey.interestOps(acceptKey.interestOps() + SelectionKey.OP_WRITE);
                        //把未写完的数据挂到selectKey上
                        acceptKey.attach(byteBuffer);
                    }
                } else if(selectionKey.isWritable()) {
                    ByteBuffer byteBuffer = (ByteBuffer)selectionKey.attachment();
                    SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
                    int write = socketChannel.write(byteBuffer);
                    log.info("write2={}", write);
                    //清理操作
                    if(!byteBuffer.hasRemaining()) {
                        selectionKey.attach(null);//清除附件ByteBuffer
                        //不需要关注write事件
                        selectionKey.interestOps(selectionKey.interestOps() - SelectionKey.OP_WRITE);
                    }
                }
            }
        }
    }
}

@Slf4j
public class NioClient {

    public static void main(String[] args) throws IOException {
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.connect(new InetSocketAddress("localhost", 8000));

        long totalCount = 0;
        while (true) {
            ByteBuffer byteBuffer = ByteBuffer.allocateDirect(1024 * 1024);
            int read = socketChannel.read(byteBuffer);
            totalCount += read;
            log.info("totalCount={}", totalCount);
            byteBuffer.clear();
        }
    }
}