在工作之余花了两个星期看完了《Java NIO》，总体来说这本书把NIO写的很详细，没有过多的废话，讲的都是重点，只是翻译的中文版看的确实吃力，英文水平太低也没办法，总算也坚持看完了。《Java NIO》这本书的重点在于第四章讲解的“选择器”，要理解透还是要反复琢磨推敲；愚钝的我花了大概3天的时间才将NIO的选择器机制理解透并能较熟练的运用，于是便写了这个聊天室程序。

下面直接上代码，jdk1.5以上经过测试，可以支持多人同时在线聊天；

将以下代码复制到项目中便可运行，源码下载地址：聊天室源码

一、服务器端

package com.chat.server;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.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.Vector;/*** 聊天室:服务端* @author zing* */
public class ChatServer implements Runnable {//选择器private Selector selector;//注册ServerSocketChannel后的选择键private SelectionKey serverKey;//标识是否运行private boolean isRun;//当前聊天室中的用户名称列表private Vector<String> unames;//时间格式化器SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");/*** 构造函数* @param port 服务端监控的端口号*/public ChatServer(int port) {isRun = true;unames = new Vector<String>();init(port);}/*** 初始化选择器和服务器套接字* * @param port 服务端监控的端口号*/private void init(int port) {try {//获得选择器实例selector = Selector.open();//获得服务器套接字实例ServerSocketChannel serverChannel = ServerSocketChannel.open();//绑定端口号serverChannel.socket().bind(new InetSocketAddress(port));//设置为非阻塞serverChannel.configureBlocking(false);//将ServerSocketChannel注册到选择器，指定其行为为"等待接受连接"serverKey = serverChannel.register(selector, SelectionKey.OP_ACCEPT);printInfo("server starting...");} catch (IOException e) {e.printStackTrace();}}@Overridepublic void run() {try {//轮询选择器选择键while (isRun) {//选择一组已准备进行IO操作的通道的key，等于1时表示有这样的keyint n = selector.select();if (n > 0) {//从选择器上获取已选择的key的集合并进行迭代Iterator<SelectionKey> iter = selector.selectedKeys().iterator();while (iter.hasNext()) {SelectionKey key = iter.next();//若此key的通道是等待接受新的套接字连接if (key.isAcceptable()) {//记住一定要remove这个key，否则之后的新连接将被阻塞无法连接服务器iter.remove();//获取key对应的通道ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();//接受新的连接返回和客户端对等的套接字通道SocketChannel channel = serverChannel.accept();if (channel == null) {continue;}//设置为非阻塞channel.configureBlocking(false);//将这个套接字通道注册到选择器，指定其行为为"读"channel.register(selector, SelectionKey.OP_READ);}//若此key的通道的行为是"读"if (key.isReadable()) {readMsg(key);}//若次key的通道的行为是"写"if (key.isWritable()) {writeMsg(key);}}}}} catch (IOException e) {e.printStackTrace();}}/*** 从key对应的套接字通道上读数据* @param key 选择键* @throws IOException*/private void readMsg(SelectionKey key) throws IOException {//获取此key对应的套接字通道SocketChannel channel = (SocketChannel) key.channel();//创建一个大小为1024k的缓存区ByteBuffer buffer = ByteBuffer.allocate(1024);StringBuffer sb = new StringBuffer();//将通道的数据读到缓存区int count = channel.read(buffer);if (count > 0) {//翻转缓存区(将缓存区由写进数据模式变成读出数据模式)buffer.flip();//将缓存区的数据转成Stringsb.append(new String(buffer.array(), 0, count));}String str = sb.toString();//若消息中有"open_"，表示客户端准备进入聊天界面//客户端传过来的数据格式是"open_zing"，表示名称为zing的用户请求打开聊天窗体//用户名称列表有更新，则应将用户名称数据写给每一个已连接的客户端if (str.indexOf("open_") != -1) {//客户端连接服务器String name = str.substring(5);printInfo(name + " online");unames.add(name);//获取选择器已选择的key并迭代Iterator<SelectionKey> iter = selector.selectedKeys().iterator();while (iter.hasNext()) {SelectionKey selKey = iter.next();//若不是服务器套接字通道的key，则将数据设置到此key中//并更新此key感兴趣的动作if (selKey != serverKey) {selKey.attach(unames);selKey.interestOps(selKey.interestOps() | SelectionKey.OP_WRITE);}}} else if (str.indexOf("exit_") != -1) {// 客户端发送退出命令String uname = str.substring(5);//删除此用户名称unames.remove(uname);//将"close"字符串附加到keykey.attach("close");//更新此key感兴趣的动作key.interestOps(SelectionKey.OP_WRITE);//获取选择器上的已选择的key并迭代//将更新后的名称列表数据附加到每个套接字通道key上,并重设key感兴趣的操作Iterator<SelectionKey> iter = key.selector().selectedKeys().iterator();while (iter.hasNext()) {SelectionKey selKey = iter.next();if (selKey != serverKey && selKey != key) {selKey.attach(unames);selKey.interestOps(selKey.interestOps() | SelectionKey.OP_WRITE);}}printInfo(uname + " offline");} else {// 读取客户端聊天消息String uname = str.substring(0, str.indexOf("^"));String msg = str.substring(str.indexOf("^") + 1);printInfo("("+uname+")说：" + msg);String dateTime = sdf.format(new Date());String smsg = uname + " " + dateTime + "\n  " + msg + "\n";Iterator<SelectionKey> iter = selector.selectedKeys().iterator();while (iter.hasNext()) {SelectionKey selKey = iter.next();if (selKey != serverKey) {selKey.attach(smsg);selKey.interestOps(selKey.interestOps() | SelectionKey.OP_WRITE);}}}}/*** 写数据到key对应的套接字通道* @param key* @throws IOException*/private void writeMsg(SelectionKey key) throws IOException {SocketChannel channel = (SocketChannel) key.channel();Object obj = key.attachment();//这里必要要将key的附加数据设置为空，否则会有问题key.attach("");//附加值为"close"，则取消此key，并关闭对应通道if (obj.toString().equals("close")) {key.cancel();channel.socket().close();channel.close();return;}else {//将数据写到通道channel.write(ByteBuffer.wrap(obj.toString().getBytes()));}//重设此key兴趣key.interestOps(SelectionKey.OP_READ);}private void printInfo(String str) {System.out.println("[" + sdf.format(new Date()) + "] -> " + str);}public static void main(String[] args) {ChatServer server = new ChatServer(19999);new Thread(server).start();}
}

二、客户端

1、服务类，用于与服务端交互

package com.chat.client;import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;public class ClientService {private static final String HOST = "127.0.0.1";private static final int PORT = 19999;private static SocketChannel sc;private static Object lock = new Object();private static ClientService service;public static ClientService getInstance(){synchronized (lock) {if(service == null){try {service = new ClientService();} catch (IOException e) {e.printStackTrace();}}return service;}}private ClientService() throws IOException {sc = SocketChannel.open();sc.configureBlocking(false);sc.connect(new InetSocketAddress(HOST, PORT));}public void sendMsg(String msg) {try {while (!sc.finishConnect()) {}sc.write(ByteBuffer.wrap(msg.getBytes()));} catch (IOException e) {e.printStackTrace();}}public String receiveMsg() {ByteBuffer buffer = ByteBuffer.allocate(1024);buffer.clear();StringBuffer sb = new StringBuffer();int count = 0;String msg = null;try {while ((count = sc.read(buffer)) > 0) {sb.append(new String(buffer.array(), 0, count));}if (sb.length() > 0) {msg = sb.toString();if ("close".equals(sb.toString())) {msg = null;sc.close();sc.socket().close();}}} catch (IOException e) {e.printStackTrace();}return msg;}}

2、登陆窗体，用户设置名称

package com.chat.client;import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;/*** 设置名称窗体* * @author zing* */
public class SetNameFrame extends JFrame {private static final long serialVersionUID = 1L;private static JTextField txtName;// 文本框private static JButton btnOK;// ok按钮private static JLabel label;// 标签public SetNameFrame() {this.setLayout(null);Toolkit kit = Toolkit.getDefaultToolkit();int w = kit.getScreenSize().width;int h = kit.getScreenSize().height;this.setBounds(w / 2 - 230 / 2, h / 2 - 200 / 2, 230, 200);this.setTitle("设置名称");this.setDefaultCloseOperation(EXIT_ON_CLOSE);this.setResizable(false);txtName = new JTextField(4);this.add(txtName);txtName.setBounds(10, 10, 100, 25);btnOK = new JButton("OK");this.add(btnOK);btnOK.setBounds(120, 10, 80, 25);label = new JLabel("[w:" + w + ",h:" + h + "]");this.add(label);label.setBounds(10, 40, 200, 100);label.setText("<html>在上面的文本框中输入名字<br/>显示器宽度：" + w + "<br/>显示器高度：" + h+ "</html>");btnOK.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {String uname = txtName.getText();ClientService service = ClientService.getInstance();ChatFrame chatFrame = new ChatFrame(service, uname);chatFrame.show();setVisible(false);}});}public static void main(String[] args) {SetNameFrame setNameFrame = new SetNameFrame();setNameFrame.setVisible(true);}}

3、聊天室窗体

package com.chat.client;import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;/*** 聊天室窗体* @author zing**/
public class ChatFrame {private JTextArea readContext = new JTextArea(18, 30);// 显示消息文本框private JTextArea writeContext = new JTextArea(6, 30);// 发送消息文本框private DefaultListModel modle = new DefaultListModel();// 用户列表模型private JList list = new JList(modle);// 用户列表private JButton btnSend = new JButton("发送");// 发送消息按钮private JButton btnClose = new JButton("关闭");// 关闭聊天窗口按钮private JFrame frame = new JFrame("ChatFrame");// 窗体界面private String uname;// 用户姓名private ClientService service;// 用于与服务器交互private boolean isRun = false;// 是否运行public ChatFrame(ClientService service, String uname) {this.isRun = true;this.uname = uname;this.service = service;}// 初始化界面控件及事件private void init() {frame.setLayout(null);frame.setTitle(uname + " 聊天窗口");frame.setSize(500, 500);frame.setLocation(400, 200);//设置可关闭frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//不能改变窗体大小frame.setResizable(false);//聊天消息显示区带滚动条JScrollPane readScroll = new JScrollPane(readContext);readScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);frame.add(readScroll);//消息编辑区带滚动条JScrollPane writeScroll = new JScrollPane(writeContext);writeScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);frame.add(writeScroll);frame.add(list);frame.add(btnSend);frame.add(btnClose);readScroll.setBounds(10, 10, 320, 300);readContext.setBounds(0, 0, 320, 300);readContext.setEditable(false);//设置为不可编辑readContext.setLineWrap(true);// 自动换行writeScroll.setBounds(10, 315, 320, 100);writeContext.setBounds(0, 0, 320, 100);writeContext.setLineWrap(true);// 自动换行list.setBounds(340, 10, 140, 445);btnSend.setBounds(150, 420, 80, 30);btnClose.setBounds(250, 420, 80, 30);//窗体关闭事件frame.addWindowListener(new WindowAdapter() {@Overridepublic void windowClosing(WindowEvent e) {isRun = false;service.sendMsg("exit_" + uname);System.exit(0);}});//发送按钮事件btnSend.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {String msg = writeContext.getText().trim();if(msg.length() > 0){service.sendMsg(uname + "^" + writeContext.getText());}//发送消息后，去掉编辑区文本，并获得光标焦点writeContext.setText(null);writeContext.requestFocus();}});//关闭按钮事件btnClose.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {isRun = false;service.sendMsg("exit_" + uname);System.exit(0);}});//右边名称列表选择事件list.addListSelectionListener(new ListSelectionListener() {@Overridepublic void valueChanged(ListSelectionEvent e) {// JOptionPane.showMessageDialog(null,// list.getSelectedValue().toString());}});//消息编辑区键盘按键事件writeContext.addKeyListener(new KeyListener() {@Overridepublic void keyTyped(KeyEvent e) {// TODO Auto-generated method stub}//按下键盘按键后释放@Overridepublic void keyReleased(KeyEvent e) {//按下enter键发送消息if(e.getKeyCode() == KeyEvent.VK_ENTER){String msg = writeContext.getText().trim();if(msg.length() > 0){service.sendMsg(uname + "^" + writeContext.getText());}writeContext.setText(null);writeContext.requestFocus();}}@Overridepublic void keyPressed(KeyEvent e) {// TODO Auto-generated method stub}});}// 此线程类用于轮询读取服务器发送的消息private class MsgThread extends Thread {@Overridepublic void run() {while (isRun) {String msg = service.receiveMsg();if (msg != null) {//若是名称列表数据，则更新聊天窗体右边的列表if (msg.indexOf("[") != -1 && msg.lastIndexOf("]") != -1) {msg = msg.substring(1, msg.length() - 1);String[] userNames = msg.split(",");modle.removeAllElements();for (int i = 0; i < userNames.length; i++) {modle.addElement(userNames[i].trim());}} else {//将聊天数据设置到聊天消息显示区String str = readContext.getText() + msg;readContext.setText(str);readContext.selectAll();//保持滚动条在最下面}}}}}// 显示界面public void show() {this.init();service.sendMsg("open_" + uname);MsgThread msgThread = new MsgThread();msgThread.start();this.frame.setVisible(true);}
}