Java nio Socket非阻塞模式

NIO 有一个主要的类Selector,这个类似一个观察者，只要我们把需要探知的socketchannel告诉Selector,我们接着做别的事情，当有 事件发生时，他会通知我们，传回一组SelectionKey,我们读取这些Key,就会获得我们刚刚注册过的socketchannel,然后，我们从 这个Channel中读取数据，放心，包准能够读到，接着我们可以处理这些数据。

Selector内部原理实际是在做一个对所注册的channel的轮询访问，不断的轮询(目前就这一个算法)，一旦轮询到一个channel有所注册的事情发生，比如数据来了，他就会站起来报告，交出一把钥匙，让我们通过这把钥匙来读取这个channel的内容。

jdk供的无阻塞I/O（NIO）有效解决了多线程服务器存在的线程开销问题，但在使用上略显得复杂一些。在NIO中使用多线程，主要目的已不是为了应对 每个客户端请求而分配独立的服务线程，而是通过多线程充分使用用多个CPU的处理能力和处理中的等待时间，达到提高服务能力的目的。

server端代码:

public class HelloWorldServer { static int BLOCK = 1024; static String name = ""; protected Selector selector; protected ByteBuffer clientBuffer = ByteBuffer.allocate(BLOCK); protected CharsetDecoder decoder; static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder(); public HelloWorldServer(int port) throws IOException { selector = this.getSelector(port); Charset charset = Charset.forName("GB2312"); decoder = charset.newDecoder(); } // 获取Selector protected Selector getSelector(int port) throws IOException { ServerSocketChannel server = ServerSocketChannel.open(); Selector sel = Selector.open(); server.socket().bind(new InetSocketAddress(port)); server.configureBlocking(false); server.register(sel, SelectionKey.OP_ACCEPT); return sel; } // 监听端口 public void listen() { try { for (;;) { selector.select(); Iterator iter = selector.selectedKeys().iterator(); while (iter.hasNext()) { SelectionKey key = (SelectionKey) iter.next(); iter.remove(); process(key); } } } catch (IOException e) { e.printStackTrace(); } } // 处理事件 protected void process(SelectionKey key) throws IOException { if (key.isAcceptable()) { // 接收请求 ServerSocketChannel server = (ServerSocketChannel) key.channel(); SocketChannel channel = server.accept(); //设置非阻塞模式 channel.configureBlocking(false); channel.register(selector, SelectionKey.OP_READ); } else if (key.isReadable()) { // 读信息 SocketChannel channel = (SocketChannel) key.channel(); int count = channel.read(clientBuffer); if (count > 0) { clientBuffer.flip(); CharBuffer charBuffer = decoder.decode(clientBuffer); name = charBuffer.toString(); // System.out.println(name); SelectionKey sKey = channel.register(selector, SelectionKey.OP_WRITE); sKey.attach(name); } else { channel.close(); } clientBuffer.clear(); } else if (key.isWritable()) { // 写事件 SocketChannel channel = (SocketChannel) key.channel(); String name = (String) key.attachment(); ByteBuffer block = encoder.encode(CharBuffer .wrap("Hello !" + name)); channel.write(block); //channel.close(); } } public static void main(String[] args) { int port = 8888; try { HelloWorldServer server = new HelloWorldServer(port); System.out.println("listening on " + port); server.listen(); } catch (IOException e) { e.printStackTrace(); } } }

client端代码:

public class HelloWorldClient { static int SIZE = 10; static InetSocketAddress ip = new InetSocketAddress("localhost", 8888); static CharsetEncoder encoder = Charset.forName("GB2312").newEncoder(); static class Message implements Runnable { protected String name; String msg = ""; public Message(String index) { this.name = index; } public void run() { try { long start = System.currentTimeMillis(); //打开Socket通道 SocketChannel client = SocketChannel.open(); //设置为非阻塞模式 client.configureBlocking(false); //打开选择器 Selector selector = Selector.open(); //注册连接服务端socket动作 client.register(selector, SelectionKey.OP_CONNECT); //连接 client.connect(ip); //分配内存 ByteBuffer buffer = ByteBuffer.allocate(8 * 1024); int total = 0; _FOR: for (;;) { selector.select(); Iterator iter = selector.selectedKeys().iterator(); while (iter.hasNext()) { SelectionKey key = (SelectionKey) iter.next(); iter.remove(); if (key.isConnectable()) { SocketChannel channel = (SocketChannel) key .channel(); if (channel.isConnectionPending()) channel.finishConnect(); channel .write(encoder .encode(CharBuffer.wrap(name))); channel.register(selector, SelectionKey.OP_READ); } else if (key.isReadable()) { SocketChannel channel = (SocketChannel) key .channel(); int count = channel.read(buffer); if (count > 0) { total += count; buffer.flip(); while (buffer.remaining() > 0) { byte b = buffer.get(); msg += (char) b; } buffer.clear(); } else { client.close(); break _FOR; } } } } double last = (System.currentTimeMillis() - start) * 1.0 / 1000; System.out.println(msg + "used time :" + last + "s."); msg = ""; } catch (IOException e) { e.printStackTrace(); } } } public static void main(String[] args) throws IOException { String names[] = new String[SIZE]; for (int index = 0; index < SIZE; index++) { names[index] = "jeff[" + index + "]"; new Thread(new Message(names[index])).start(); } } }