java nio

0、java nio编程比较复杂，坑多。可以看一些文章，如nio通道-几个注意点，SocketChannel续2-各种注意点。

1、go语言需要nio吗？ go支持协程，所以在代码层面，就是顺序编程，就像阻塞IO一样，一台机器起几万个协程。但其底层实现也是非阻塞的，和java一样，都是epoll

2、用一个聊天室的例子学习一下java nio

package gaofeng.nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.Channel;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.nio.charset.Charset;import java.util.Iterator;public class Server {    private Charset charset = Charset.forName("UTF-8");    public static void main(String[] args) throws IOException {new Server().start();}public void start() throws IOException {Selector selector = Selector.open();ServerSocketChannel serverChannel = ServerSocketChannel.open();serverChannel.bind(new InetSocketAddress(8088));serverChannel.configureBlocking(false);serverChannel.register(selector, SelectionKey.OP_ACCEPT);System.out.println("服务端开始监听8080端口...");while(true){if(selector.select()==0){System.out.println("selector.select()==0");continue;}for (Iterator<SelectionKey> iterator = selector.selectedKeys().iterator(); iterator.hasNext();) {SelectionKey key = iterator.next();iterator.remove();if(key.isAcceptable()){SocketChannel oneSocket = serverChannel.accept();System.out.println("one user:" + oneSocket.getRemoteAddress());oneSocket.configureBlocking(false);oneSocket.register(selector, SelectionKey.OP_READ);oneSocket.write(charset.encode("请输入您的昵称:"));}if(key.isReadable()){ByteBuffer buff = ByteBuffer.allocate(1024);SocketChannel oneSocket = (SocketChannel) key.channel();try{while(oneSocket.read(buff)>0){System.out.print("---");}buff.flip();String info = charset.decode(buff).toString();System.out.println(oneSocket.getRemoteAddress() + " info:"+info);if(info.endsWith("%#%")){broadcast(selector,oneSocket,info.substring(0, info.length()-"%#$".length())+"进入了房间");}else{broadcast(selector,oneSocket,info.replace("%#%", "说:"));}}catch(Exception e){key.cancel();oneSocket.close();e.printStackTrace();}}}}}private void broadcast(Selector selector,SocketChannel self,String info){for (SelectionKey key : selector.keys()) {Channel channel = key.channel();if(channel instanceof SocketChannel && channel!=self){try {System.out.println("broadcast:" + info);((SocketChannel)channel).write(charset.encode(info));} catch (IOException e) {e.printStackTrace();}}}}}

package gaofeng.nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.nio.charset.Charset;import java.util.Iterator;import java.util.Scanner;public class Client {private String username = null;private Charset charset = Charset.forName("UTF-8");    public static void main(String[] args) throws IOException {new Client().start();}public void start() throws IOException {final Selector selector = Selector.open();SocketChannel socket = SocketChannel.open(new InetSocketAddress("127.0.0.1", 8088));socket.configureBlocking(false);socket.register(selector, SelectionKey.OP_READ);new Thread(){public void run(){while(true){try {if(selector.select()==0){System.out.println("selector.select()==0");continue;}} catch (IOException e) {e.printStackTrace();}for (Iterator<SelectionKey> iterator = selector.selectedKeys().iterator(); iterator.hasNext();) {SelectionKey key = iterator.next();iterator.remove();if(key.isReadable()){ByteBuffer buff = ByteBuffer.allocate(1024);SocketChannel oneSocket = (SocketChannel) key.channel();try{while(oneSocket.read(buff)>0){System.out.print("---");}buff.flip();String info = charset.decode(buff).toString();System.out.println(info);}catch(Exception e){e.printStackTrace();}}}}}}.start();Scanner scan = new Scanner(System.in);while(scan.hasNextLine()){String line = scan.nextLine();if(line.isEmpty()){System.out.println(line.isEmpty());continue;}if("exit".equals(line)){break;}String info;if(username==null){username=line;info = username+"%#%";}else{info = username+"%#%"+line;}socket.write(charset.encode(info));}scan.close();System.out.println("exit");System.exit(0);}}