无锡达内教育java培训班一般多少钱

什么是NIO？

同步非阻塞

包括Selector，这是多路复用器，selector会不断轮询注册的channel，如果某个channel上发生了读写事件，selector就会将这些channel获取出来，我们通过SelectionKey获取有读写事件的channel，就可以进行IO操作。一个Selector就通过一个线程，就可以轮询成千上万的channel，这就意味着你的服务端可以接入成千上万的客户端。

public class NioDemo implements Runnable { public int id = 100001; public int bufferSize = 2048; @Override public void run() { init(); } public void init()

{ try {

// 创建通道和选择器 ServerSocketChannel socketChannel = ServerSocketChannel.open(); Selector selector = Selector.open(); InetSocketAddress inetSocketAddress = new InetSocketAddress( InetAddress.getLocalHost(), 4700); socketChannel.socket().bind(inetSocketAddress);

// 设置通道非阻塞 绑定选择器 socketChannel.configureBlocking(false); socketChannel.register(selector, SelectionKey.OP_ACCEPT).attach( id++); System.out.println("Server started .... port:4700"); listener(selector); } catch (Exception e) { } }

public void listener(Selector in_selector) { try { while (true) { Thread.sleep(1 * 1000); in_selector.select(); // 阻塞 直到有就绪事件为止 Set readySelectionKey = in_selector .selectedKeys(); Iterator it = readySelectionKey.iterator(); while (it.hasNext()) { SelectionKey selectionKey = it.next(); // 判断是哪个事件 if (selectionKey.isAcceptable()) {

// 客户请求连接 System.out.println(selectionKey.attachment() + " - 接受请求事件");

// 获取通道 接受连接, // 设置非阻塞模式(必须)，同时需要注册 读写数据的事件，这样有消息触发时才能捕获 ServerSocketChannel serverSocketChannel = (ServerSocketChannel) selectionKey .channel(); serverSocketChannel .accept() .configureBlocking(false) .register( in_selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE).attach(id++); System.out .println(selectionKey.attachment() + " - 已连接"); // 下面这种写法是有问题的 不应该在serverSocketChannel上面注册 /* * serverSocketChannel.configureBlocking(false); * serverSocketChannel.register(in_selector, * SelectionKey.OP_READ); * serverSocketChannel.register(in_selector, * SelectionKey.OP_WRITE); */ } if (selectionKey.isReadable()) {// 读数据 System.out.println(selectionKey.attachment() + " - 读数据事件"); SocketChannel clientChannel = (SocketChannel) selectionKey.channel(); ByteBuffer receiveBuf = ByteBuffer.allocate(bufferSize); clientChannel.read(receiveBuf); System.out.println(selectionKey.attachment() + " - 读取数据：" + getString(receiveBuf)); } if (selectionKey.isWritable()) {// 写数据 System.out.println(selectionKey.attachment() + " - 写数据事件"); SocketChannel clientChannel = (SocketChannel) selectionKey.channel(); ByteBuffer sendBuf = ByteBuffer.allocate(bufferSize); String sendText = "hello\n"; sendBuf.put(sendText.getBytes()); sendBuf.flip(); //写完数据后调用此方法 clientChannel.write(sendBuf); } if (selectionKey.isConnectable()) { System.out.println(selectionKey.attachment() + " - 连接事件"); } // 必须removed 否则会继续存在，下一次循环还会进来, // 注意removed 的位置，针对一个.next() remove一次 it.remove(); } } } catch (Exception e) { System.out.println("Error - " + e.getMessage()); e.printStackTrace(); } } /** * ByteBuffer 转换 String * * @param buffer * @return */ public static String getString(ByteBuffer buffer) { String string = ""; try { for (int i = 0; i < buffer.position(); i++) { string += (char) buffer.get(i); } return string; } catch (Exception ex) { ex.printStackTrace(); return ""; } }}