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：

 1 /*
 2  * 流程总结：
 3   * 1.初始时，只对accept事件感兴趣，selectionkey只有accept事件
 4   * 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
 5   * 3.不断循环selectionkey的键集合
 6  */
 7
 8 Selector selector = Selector.open();
 9 ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
10 serverSocketChannel.configureBlocking(false); // 设置为非阻塞
11
12 // 绑定监听端口号
13 serverSocketChannel.bind(new InetSocketAddress(8899));
14
15 serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); // 对连接事件感兴趣
16
17 while (true) {
18     Set<SelectionKey> keys = selector.selectedKeys();
19
20     Iterator<SelectionKey> iterator = keys.iterator();
21
22     while(iterator.hasNext()) {
23         SelectionKey selectionKey = iterator.next();
24
25         if(selectionKey.isAcceptable()) {
26             ServerSocketChannel serverSocketChannel1 = (ServerSocketChannel) selectionKey.channel();
27             SocketChannel socketChannel = serverSocketChannel1.accept(); // 此处阻塞
28             socketChannel.configureBlocking(false);
29
30             socketChannel.register(selector, SelectionKey.OP_READ);
31
32             iterator.remove();
33         } 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
34             SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
35
36             while (true) {
37                 ByteBuffer byteBuffer = ByteBuffer.allocate(512);
38                 byteBuffer.clear();
39                 int read = socketChannel.read(byteBuffer);
40
41                 if(read <= 0) {
42                     break; // 数据已接收完毕
43                 }
44
45                 byteBuffer.flip();
46                 socketChannel.write(byteBuffer);
47
48             }
49
50             iterator.remove();
51
52         }
53
54
55     }
56
57 }