NIO 多人聊天室

一前言

在家休息没事，敲敲代码，用NIO写个简易的仿真聊天室。下面直接讲聊天室设计和编码。对NIO不了解的朋友，推荐一个博客，里面写的很棒：

https://javadoop.com/     里面有NIO的部分

二设计

1.进入的时候，提示输入聊天昵称，重复的话，重新输入，成功后进到聊天室。

2.成功进到聊天室，广播通知，XXX进到了聊天室；离开聊天室，XXX离开了聊天室。

3.@XXX 给XXX发消息，只有双方可以看到。

4.服务端收到的内容会转发给其他客户端。

三代码

目前版本（设计工程3，4有待改进）

服务端：

 package com.lee.demo.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.HashSet;
 import java.util.Iterator;
 import java.util.Set;

 public class ChatServer {

     private Selector  selector = null;
     private Charset charset = Charset.forName("UTF-8");
     public static final int PORT = 8765;
     private static String USER_CONTENT_SPILIT = "#";
     private static HashSet<String> users = new HashSet<String>();

     public void init() throws IOException {
         selector = Selector.open();
         ServerSocketChannel server = ServerSocketChannel.open();
         server.socket().bind(new InetSocketAddress(PORT));
         // 将其注册到 Selector 中，监听 OP_ACCEPT 事件
         server.configureBlocking(false);
         server.register(selector, SelectionKey.OP_ACCEPT);

         while (true) {
             int readyChannels = selector.select();
             if (readyChannels == 0) {
                 continue;
             }
             Set<SelectionKey> readyKeys = selector.selectedKeys();
             // 遍历
             Iterator<SelectionKey> iterator = readyKeys.iterator();
             while (iterator.hasNext()) {
                 SelectionKey key = iterator.next();
                 iterator.remove();
                 dealWithKey(server, key);

             }
         }

     }

     private void dealWithKey(ServerSocketChannel server, SelectionKey key) throws IOException {
         String content = null;
         if (key.isAcceptable()) {
             // 有已经接受的新的到服务端的连接
             SocketChannel socketChannel = server.accept();

             // 有新的连接并不代表这个通道就有数据，
             // 这里将这个新的 SocketChannel 注册到 Selector，监听 OP_READ 事件，等待数据
             socketChannel.configureBlocking(false);
             socketChannel.register(selector, SelectionKey.OP_READ);
             //将此对应的channel设置为准备接受其他客户端请求
             key.interestOps(SelectionKey.OP_ACCEPT);
             System.out.println("Server is listening from client " + socketChannel.getRemoteAddress());
             socketChannel.write(charset.encode("Please input your name: "));

         } else if (key.isReadable()) {
             // 有数据可读
             // 上面一个 if 分支中注册了监听 OP_READ 事件的 SocketChannel
             SocketChannel socketChannel = (SocketChannel) key.channel();
             ByteBuffer readBuffer = ByteBuffer.allocate(1024);
             int num = socketChannel.read(readBuffer);
             if (num > 0) {
                 content = new String(readBuffer.array()).trim();
                 // 处理进来的数据...
                 System.out.println("Server is listening from client " +
                                     socketChannel.getRemoteAddress() +
                                     " data received is: " +
                                     content);
 /*                ByteBuffer buffer = ByteBuffer.wrap("返回给客户端的数据...".getBytes());
                 socketChannel.write(buffer);*/
                 //将此对应的channel设置为准备下一次接受数据
                 key.interestOps(SelectionKey.OP_READ);

                 String[] arrayContent = content.split(USER_CONTENT_SPILIT);
                 //注册用户
                 if(arrayContent != null && arrayContent.length ==1) {
                     String name = arrayContent[0];
                     if(users.contains(name)) {
                         socketChannel.write(charset.encode("system message: user exist, please change a name"));

                     } else {
                         users.add(name);
                         int number = OnlineNum(selector);
                         String message = "welcome " + name + " to chat room! Online numbers:" + number;
                         broadCast(selector, null, message);
                     }
                 }
                 //注册完了，发送消息
                 else if(arrayContent != null && arrayContent.length >1){
                     String name = arrayContent[0];
                     String message = content.substring(name.length() + USER_CONTENT_SPILIT.length());
                     message = name + " say " + message;
                     if(users.contains(name)) {
                         //不回发给发送此内容的客户端
                         broadCast(selector, socketChannel, message);
                     }
                 }
             } else if (num == -1) {
                 // -1 代表连接已经关闭
                 socketChannel.close();
             }
         }
     }

     private void broadCast(Selector selector, SocketChannel except, String content) throws IOException {
         //广播数据到所有的SocketChannel中
         for(SelectionKey key : selector.keys())
         {
             Channel targetchannel = key.channel();
             //如果except不为空，不回发给发送此内容的客户端
             if(targetchannel instanceof SocketChannel && targetchannel!=except)
             {
                 SocketChannel dest = (SocketChannel)targetchannel;
                 dest.write(charset.encode(content));
             }
         }
     }

     public static int OnlineNum(Selector selector) {
         int res = 0;
         for(SelectionKey key : selector.keys())
         {
             Channel targetchannel = key.channel();
             if(targetchannel instanceof SocketChannel)
                 res++;
         }
         return res;
     }

     public static void main(String[] args) throws IOException {
         new ChatServer().init();
     }

 }

客户端：

 package com.lee.demo.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;
 import java.util.Set;

 public abstract class ChatClient {

     private Selector selector = null;
     public static final int port = 8765;
     private Charset charset = Charset.forName("UTF-8");
     private SocketChannel sc = null;
     private String name = "";
     private static String USER_EXIST = "system message: user exist, please change a name";
     private static String USER_CONTENT_SPILIT = "#";

     public void init() throws IOException
     {
         selector = Selector.open();
         //连接远程主机的IP和端口
         sc = SocketChannel.open(new InetSocketAddress("127.0.0.1", port));
         sc.configureBlocking(false);
         sc.register(selector, SelectionKey.OP_READ);
         //开辟一个新线程来读取服务器端的数据
         new Thread(new ClientThread()).start();
         //在主线程中 从键盘读取数据输入到服务器端
         Scanner scan = new Scanner(System.in);
         try {
             while (scan.hasNextLine()) {
                 String line = scan.nextLine();
                 if ("".equals(line))
                     continue; // 不允许发空消息
                 if ("".equals(name)) {
                     name = line;
                     line = name + USER_CONTENT_SPILIT;
                 } else {
                     line = name + USER_CONTENT_SPILIT + line;
                 }
                 sc.write(charset.encode(line));// sc既能写也能读，这边是写
             }
         } finally {
             scan.close();
         }

     }
     private class ClientThread implements Runnable
     {
         public void run()
         {
             try
             {
                 while(true) {
                     int readyChannels = selector.select();
                     if(readyChannels == 0) continue;
                     //可以通过这个方法，知道可用通道的集合
                     Set<SelectionKey> selectedKeys = selector.selectedKeys();
                     Iterator<SelectionKey> keyIterator = selectedKeys.iterator();
                     while(keyIterator.hasNext()) {
                          SelectionKey sk = (SelectionKey) keyIterator.next();
                          keyIterator.remove();
                          dealWithSelectionKey(sk);
                     }
                 }
             }
             catch (IOException io)
             {}
         }

         private void dealWithSelectionKey(SelectionKey sk) throws IOException {
             if(sk.isReadable())
             {
                 //使用 NIO 读取 Channel中的数据，这个和全局变量sc是一样的，因为只注册了一个SocketChannel
                 //sc既能写也能读，这边是读
                 SocketChannel sc = (SocketChannel)sk.channel();

                 ByteBuffer buff = ByteBuffer.allocate(1024);
                 String content = "";
                 while(sc.read(buff) > 0)
                 {
                     buff.flip();
                     content += charset.decode(buff);
                 }
                 //若系统发送通知名字已经存在，则需要换个昵称
                 if(USER_EXIST.equals(content)) {
                     name = "";
                 }
                 System.out.println(content);
                 sk.interestOps(SelectionKey.OP_READ);
             }
         }
     }

 }

自己生成一个类，将Client这个抽象类继承，执行就可以了。观看结果的时候，会有个小地方需要注意，就是Eclipse中，console的结果，需要开启多个控制台，要不会发生混乱。

方法：

第一步：

第二步：

左侧红框，pin console ，作用是锁定console，固定显示选择的线程的输出；
 右侧红框，作用是线程选择显示哪个线程的输出。