reactor模式前序（二）：NIO WEB服务器设计

前文介绍了传统IO的WEB经典服务器 reactor模式前序：传统IO的WEB服务器设计

下面看看JAVA NIO的WEB服务器设计

NIO是基于事件驱动的，对于NIO来说，重要组件是Selector，其服务器代码为：

/*
 * 流程总结：
  * 1.初始时，只对accept事件感兴趣，selectionkey只有accept事件
  * 2.当有连接进来时，处理完accept之后，对读事件感兴趣，selectionkey增加键read
  * 3.不断循环selectionkey的键集合
 */

Selector selector = Selector.open();
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false); // 设置为非阻塞

// 绑定监听端口号
serverSocketChannel.bind(new InetSocketAddress(8899));

serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); // 对连接事件感兴趣

while (true) {
    Set<SelectionKey> keys = selector.selectedKeys();

    Iterator<SelectionKey> iterator = keys.iterator();

    while(iterator.hasNext()) {
        SelectionKey selectionKey = iterator.next();

        if(selectionKey.isAcceptable()) {
            ServerSocketChannel serverSocketChannel1 = (ServerSocketChannel) selectionKey.channel();
            SocketChannel socketChannel = serverSocketChannel1.accept(); // 此处阻塞
            socketChannel.configureBlocking(false);

            socketChannel.register(selector, SelectionKey.OP_READ);

            iterator.remove();
        } else if(selectionKey.isReadable()) { // 完成功能：从客户端接收数据并且原样返回给客户端
            SocketChannel socketChannel = (SocketChannel) selectionKey.channel();

            while (true) {
                ByteBuffer byteBuffer = ByteBuffer.allocate(512);
                byteBuffer.clear();
                int read = socketChannel.read(byteBuffer);

                if(read <= 0) {
                    break; // 数据已接收完毕
                }

                byteBuffer.flip();
                socketChannel.write(byteBuffer);

            }

            iterator.remove();

        }


    }

}