服务端：
package nio; import java.io.IOException; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.nio.ByteBuffer; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.ServerSocketChannel; import java.nio.channels.SocketChannel; import java.text.SimpleDateFormat; import java.util.Date; import java.util.Iterator; import java.util.Vector; //与Selector一起使用时，Channel必须处于非阻塞模式下。这意味着不能将FileChannel与Selector一起使用，因为FileChannel不能切换到非阻塞模式。而套接字通道都可以。 /*多人聊天室：服务端执行机制（设置通道对某个事件感兴趣，是设置某个事件已就绪，具体得看事件觉得，比如读事件就得通道有数据才能算就绪） 1、创建选择器、服务端通道、服务端socket、绑定端口 2、将服务端通道注册到选择器中，并设置服务端通道对接收连接感兴趣 3、selector.select()会阻塞，知道至少一个通道就绪，然后获取所有就绪的通道 4、接下来就是三个执行动作了，接收连接，读取消息，发送消息，虽然第一次循环肯定是接收连接 5、接收连接：selector在接收到通道连接的事件之后就会为该连接创建新的socketChannel用于和客户端的通信，将该通道注册到选择器，并且设置其感兴趣的事件是读 6、读取消息：当通道有数据发送过来的时候，读取客户端消息，通过attach()给其余各个channel设置附加对象数据，之后设置其感兴趣的事件是写 7、发送消息：由于设置通道对写事件感兴趣时就可对判断通道对该事件是否就绪，获取attach里面的对象，给客户端发送数据 如果服务端的channel在发送消息之前收到2个通知，前面的通知会被覆盖，造成消息丢失 public class ChatServer { public static void main(String[] args) { ChatServerThread chatServerThread=new ChatServerThread(); new Thread(chatServerThread).start(); } } class ChatServerThread implements Runnable{ private Selector selector; private SelectionKey serverKey; private Vector<String> usernames; private static final int PORT=9999; SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); public ChatServerThread(){ usernames=new Vector<>(); init(); } public void init(){ try { //获取选择器 selector=Selector.open(); //获取服务端通道 ServerSocketChannel serverSocketChannel=ServerSocketChannel.open(); //获取服务端socket ServerSocket socket=serverSocketChannel.socket(); //socket绑定端口 socket.bind(new InetSocketAddress(PORT)); //跟selector配合时channel要设置成非阻塞状态 serverSocketChannel.configureBlocking(false); //将通道注册到selector，并且监听该通道对连接时间感兴趣 serverKey=serverSocketChannel.register(selector,SelectionKey.OP_ACCEPT); printInfo("server starting......."); }catch (IOException e){ e.printStackTrace(); } } @Override public void run(){ try { while(true){ //select()阻塞到至少有一个通道注册的事件上就绪了。 int count=selector.select(); if(count>0){ //获取已选择的键集合来访问就绪的通道 Iterator<SelectionKey> iterator=selector.selectedKeys().iterator(); while(iterator.hasNext()){ SelectionKey key=iterator.next(); //如果该事件的通道等待接收新的套接字连接 if(key.isAcceptable()){ System.out.println(key.toString()+":接收"); //Selector不会自己从已选择键集中移除SelectionKey实例。必须在处理完通道时自己移除。不然下次该通道变成就绪时，Selector会再次将其放入已选择键集中。 iterator.remove(); //获取该事件触发的通道 ServerSocketChannel serverSocketChannel=(ServerSocketChannel)key.channel(); //监听新进来的连接，注册通道并且监听对读事件感兴趣 SocketChannel socketChannel=serverSocketChannel.accept(); socketChannel.configureBlocking(false); socketChannel.register(selector,SelectionKey.OP_READ); } //如果该事件的通道有数据可读状态 if(key.isValid()&& key.isReadable()){ readMSg(key); } //如果该事件的通道是写数据状态 if(key.isValid() && key.isWritable()){ writeMsg(key); } } } } }catch (IOException e){ e.printStackTrace(); } } //读取通道数据 private void readMSg(SelectionKey key){ SocketChannel channel=null; try { //获取该事件的通道 channel=(SocketChannel) key.channel(); //设置缓存区 ByteBuffer buffer= ByteBuffer.allocate(1024); //将通道数据写到缓存区 int count=channel.read(buffer); StringBuffer buf=new StringBuffer(); if(count>0){ //切换读状态 buffer.flip(); buf.append(new String(buffer.array(),0,count)); } String msg=buf.toString(); //如果次数据是客户端连接时发送的数据 if(msg.indexOf("open_")!=-1){ String name=msg.substring(5); printInfo(name+"--->online"); //将用户添加到上线用户列表中 usernames.add(name); //获取已就绪的通道集合 Iterator<SelectionKey> iter=selector.selectedKeys().iterator(); while ((iter.hasNext())){ SelectionKey skey=iter.next(); //该事件不是道路端口通道的事件 if(skey!=serverKey){ //可以将一个对象或者更多信息附着到SelectionKey上，这样就能方便的识别某个给定的通道 skey.attach(usernames); //更新通道感兴趣的事件 skey.interestOps(skey.interestOps() | SelectionKey.OP_WRITE); } } }else if(msg.indexOf("exit_")!=-1){ String username=msg.substring(5); usernames.remove(username); key.attach("close"); //要退出当前channel加上close的标示，并把兴趣转为写，如果write中收到close，则中断通道 key.interestOps(SelectionKey.OP_WRITE); Iterator<SelectionKey> iter=selector.selectedKeys().iterator(); printInfo(username+"下线啦！"); while(iter.hasNext()){ SelectionKey skey=iter.next(); //相当于服务器通道内部之间数据的传输，并通知该通道写就绪了 skey.attach(username+"下线啦！"); skey.interestOps(skey.interestOps()|SelectionKey.OP_WRITE); } }else{ String uname=msg.substring(0,msg.indexOf("^")); msg=msg.substring(msg.indexOf("^")+1); printInfo("("+uname+")说："+msg); String dateTime=sdf.format(new Date()); String smsg=uname+" "+dateTime+" "+msg+" "; Iterator<SelectionKey> iter=selector.selectedKeys().iterator(); while (iter.hasNext()){ SelectionKey skey=iter.next(); skey.attach(smsg); skey.interestOps(skey.interestOps()|SelectionKey.OP_WRITE); } } buffer.clear(); }catch (IOException e){ key.cancel(); try{ channel.socket().close(); channel.close(); }catch (IOException e1){ e1.printStackTrace(); } } } //先通道写信息 private void writeMsg(SelectionKey key){ try { SocketChannel socketChannel=(SocketChannel)key.channel(); Object attachment=key.attachment(); key.attach(""); socketChannel.write(ByteBuffer.wrap(attachment.toString().getBytes())); key.interestOps(SelectionKey.OP_READ); }catch (Exception e){ e.printStackTrace(); } } private void printInfo(String str) { System.out.println("[" + sdf.format(new Date()) + "] -> " + str); } }
客户端：
package nio; import java.io.IOException; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.channels.ClosedChannelException; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.SocketChannel; import java.util.Iterator; import java.util.Scanner; public class ChatClient { public static Selector selector=null; public static SocketChannel socketChannel=null; //register()设置通道感兴趣的事件 //elect()是否返回与selectedKeys集合有关。当selectedKeys集合不为空时，select()会立即返回，但是其返回值是发生改变的keys数量，即新的就绪通道数量 //当感兴趣的事件被触发之后,就会往selectedKeys里面添加selectedKey，在执行完将selectedKey移除之后，如果事件再次被触发再次就绪之后，相同的selectedKey对象实例会再次被添加集合里面 public ChatClient(){ try { this.selector=Selector.open(); this.socketChannel=SocketChannel.open(); this.socketChannel.configureBlocking(false); this.socketChannel.connect(new InetSocketAddress("127.0.0.1",9999)); this.socketChannel.register(selector, SelectionKey.OP_CONNECT); new Thread(()->{ while(true){ try{ int count =this.selector.select(); Iterator<SelectionKey> keys=this.selector.selectedKeys().iterator(); while (keys.hasNext()){ SelectionKey key=keys.next(); if(key.isValid() && key.isConnectable()){ SocketChannel socketChannel=(SocketChannel)key.channel(); if(socketChannel.finishConnect()){ keys.remove(); socketChannel.register(this.selector,SelectionKey.OP_READ); } } if(key.isValid() && key.isReadable()){ this.readMsg(key); keys.remove(); } } }catch (IOException e){ e.printStackTrace(); } } }).start(); }catch (ClosedChannelException e){ System.out.println("Client： 失去主机连接"); e.printStackTrace(); }catch (IOException e){ e.printStackTrace(); } } private void readMsg(SelectionKey key){ try { SocketChannel socketChannel=(SocketChannel)key.channel(); ByteBuffer buffer=ByteBuffer.allocate(1024); StringBuilder stringBuilder=new StringBuilder(); int size=socketChannel.read(buffer); while(size>0){ buffer.flip(); stringBuilder.append(new String(buffer.array(),0,size)); size=socketChannel.read(buffer); } System.out.println("接收到的消息： "+stringBuilder.toString()); }catch (IOException e){ e.printStackTrace(); } } public static void main(String[] args) { try { ChatClient chatClient=new ChatClient(); System.out.println("请输入名称："); Scanner scanner=new Scanner(System.in); String name=scanner.nextLine(); String onlineStr="open_"+name; sendMsg(onlineStr); System.out.println("开始聊天吧！"); while (true){ String msg=scanner.nextLine(); if(msg.equals("close")){ String closeStr="exit_"+name; sendMsg(closeStr); break; } String sendMsg=name+"^"+msg; sendMsg(sendMsg); } }catch (Exception e){ e.printStackTrace(); } } public static void sendMsg(String msg){ try{ byte[] req=msg.getBytes(); ByteBuffer byteBuffer=ByteBuffer.wrap(req); byteBuffer.put(req); byteBuffer.flip(); socketChannel.write(byteBuffer); byteBuffer.clear(); }catch (Exception e){ e.printStackTrace(); } } }