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 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 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);
	}

}