《尚学堂java开发聊天室视频教程》是初级课程中课堂上讲解的小项目。让大家通过完成一个点对点的局域网聊天系统， 熟悉socket网络编程、多线程技术等。
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该老师讲课风格:
教师讲课深入浅出，条理清楚，层层剖析，环环相扣，论证严密，结构严谨，用思维的逻辑力量吸引学生的注意力，用理智控制课堂教学进程。学生通过听教师的讲授，不仅学到知识，也受到思维的训练，还受到教师严谨的治学态度的熏陶和感染
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本视频中较为难点是java开发聊天室了：
聊天室的设计思想是 ：在局域网下， 利用socket进行连接通信，当服务器端启动的时候，利用Thread线程不停的等待客户端的链接；当有客户端开启连
接的时候，服务器端通过IO流反馈“上线用户”信息给客户端，客户端也使用线程不停的接收服务器的信息，从而实现多人在线聊天功能。
程序中有三个类，分别 Server.Java（服务器端）、Client（客户端）、User.java（javabean）。代码如下：
Server.java（服务器端）：
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.StringTokenizer;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.border.TitledBorder;
public class Server {
private JFrame frame;
private JTextArea contentArea;
private JTextField txt_message;
private JTextField txt_max;
private JTextField txt_port;
private JButton btn_start;
private JButton btn_stop;
private JButton btn_send;
private JPanel northPanel;
private JPanel southPanel;
private JScrollPane rightPanel;
private JScrollPane leftPanel;
private JSplitPane centerSplit;
private JList userList;
private DefaultListModel listModel;
private ServerSocket serverSocket;
private ServerThread serverThread;
private ArrayList clients;
private boolean isStart = false;
// 主方法,程序执行入口
public static void main(String[] args) {
new Server();
}
// 执行消息发送
public void send() {
if (!isStart) {
JOptionPane.showMessageDialog(frame, "服务器还未启动,不能发送消息！", "错误",
JOptionPane.ERROR_MESSAGE);
return;
}
if (clients.size() == 0) {
JOptionPane.showMessageDialog(frame, "没有用户在线,不能发送消息！", "错误",
JOptionPane.ERROR_MESSAGE);
return;
}
String message = txt_message.getText().trim();
if (message == null || message.equals("")) {
JOptionPane.showMessageDialog(frame, "消息不能为空！", "错误",
JOptionPane.ERROR_MESSAGE);
return;
}
sendServerMessage(message);// 群发服务器消息
contentArea.append("服务器说：" + txt_message.getText() + "\r\n");
txt_message.setText(null);
}
// 构造放法
public Server() {
frame = new JFrame("服务器");
// 更改JFrame的图标：
//frame.setIconImage(Toolkit.getDefaultToolkit().createImage(Client.class.getResource("qq.png")));
frame.setIconImage(Toolkit.getDefaultToolkit().createImage(Server.class.getResource("qq.png")));
contentArea = new JTextArea();
contentArea.setEditable(false);
contentArea.setForeground(Color.blue);
txt_message = new JTextField();
txt_max = new JTextField("30");
txt_port = new JTextField("6666");
btn_start = new JButton("启动");
btn_stop = new JButton("停止");
btn_send = new JButton("发送");
btn_stop.setEnabled(false);
listModel = new DefaultListModel();
userList = new JList(listModel);
southPanel = new JPanel(new BorderLayout());
southPanel.setBorder(new TitledBorder("写消息"));
southPanel.add(txt_message, "Center");
southPanel.add(btn_send, "East");
leftPanel = new JScrollPane(userList);
leftPanel.setBorder(new TitledBorder("在线用户"));
rightPanel = new JScrollPane(contentArea);
rightPanel.setBorder(new TitledBorder("消息显示区"));
centerSplit = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, leftPanel,
rightPanel);
centerSplit.setDividerLocation(100);
northPanel = new JPanel();
northPanel.setLayout(new GridLayout(1, 6));
northPanel.add(new JLabel("人数上限"));
northPanel.add(txt_max);
northPanel.add(new JLabel("端口"));
northPanel.add(txt_port);
northPanel.add(btn_start);
northPanel.add(btn_stop);
northPanel.setBorder(new TitledBorder("配置信息"));
frame.setLayout(new BorderLayout());
frame.add(northPanel, "North");
frame.add(centerSplit, "Center");
frame.add(southPanel, "South");
frame.setSize(600, 400);
//frame.setSize(Toolkit.getDefaultToolkit().getScreenSize());//设置全屏
int screen_width = Toolkit.getDefaultToolkit().getScreenSize().width;
int screen_height = Toolkit.getDefaultToolkit().getScreenSize().height;
frame.setLocation((screen_width - frame.getWidth()) / 2,
(screen_height - frame.getHeight()) / 2);
frame.setVisible(true);
// 关闭窗口时事件
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
if (isStart) {
closeServer();// 关闭服务器
}
System.exit(0);// 退出程序
}
});
// 文本框按回车键时事件
txt_message.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
send();
}
});
// 单击发送按钮时事件
btn_send.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
send();
}
});
// 单击启动服务器按钮时事件
btn_start.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (isStart) {
JOptionPane.showMessageDialog(frame, "服务器已处于启动状态，不要重复启动！",
"错误", JOptionPane.ERROR_MESSAGE);
return;
}
int max;
int port;
try {
try {
max = Integer.parseInt(txt_max.getText());
} catch (Exception e1) {
throw new Exception("人数上限为正整数！");
}
if (max <= 0) {
throw new Exception("人数上限为正整数！");
}
try {
port = Integer.parseInt(txt_port.getText());
} catch (Exception e1) {
throw new Exception("端口号为正整数！");
}
if (port <= 0) {
throw new Exception("端口号 为正整数！");
}
serverStart(max, port);
contentArea.append("服务器已成功启动!人数上限：" + max + ",端口：" + port
+ "\r\n");
JOptionPane.showMessageDialog(frame, "服务器成功启动!");
btn_start.setEnabled(false);
txt_max.setEnabled(false);
txt_port.setEnabled(false);
btn_stop.setEnabled(true);
} catch (Exception exc) {
JOptionPane.showMessageDialog(frame, exc.getMessage(),
"错误", JOptionPane.ERROR_MESSAGE);
}
}
});
// 单击停止服务器按钮时事件
btn_stop.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (!isStart) {
JOptionPane.showMessageDialog(frame, "服务器还未启动，无需停止！", "错误",
JOptionPane.ERROR_MESSAGE);
return;
}
try {
closeServer();
btn_start.setEnabled(true);
txt_max.setEnabled(true);
txt_port.setEnabled(true);
btn_stop.setEnabled(false);
contentArea.append("服务器成功停止!\r\n");
JOptionPane.showMessageDialog(frame, "服务器成功停止！");
} catch (Exception exc) {
JOptionPane.showMessageDialog(frame, "停止服务器发生异常！", "错误",
JOptionPane.ERROR_MESSAGE);
}
}
});
}
// 启动服务器
public void serverStart(int max, int port) throws java.net.BindException {
try {
clients = new ArrayList();
serverSocket = new ServerSocket(port);
serverThread = new ServerThread(serverSocket, max);
serverThread.start();
isStart = true;
} catch (BindException e) {
isStart = false;
throw new BindException("端口号已被占用，请换一个！");
} catch (Exception e1) {
e1.printStackTrace();
isStart = false;
throw new BindException("启动服务器异常！");
}
}
// 关闭服务器
@SuppressWarnings("deprecation")
public void closeServer() {
try {
if (serverThread != null)
serverThread.stop();// 停止服务器线程
for (int i = clients.size() - 1; i >= 0; i--) {
// 给所有在线用户发送关闭命令
clients.get(i).getWriter().println("CLOSE");
clients.get(i).getWriter().flush();
// 释放资源
clients.get(i).stop();// 停止此条为客户端服务的线程
clients.get(i).reader.close();
clients.get(i).writer.close();
clients.get(i).socket.close();
clients.remove(i);
}
if (serverSocket != null) {
serverSocket.close();// 关闭服务器端连接
}
listModel.removeAllElements();// 清空用户列表
isStart = false;
} catch (IOException e) {
e.printStackTrace();
isStart = true;
}
}
// 群发服务器消息
public void sendServerMessage(String message) {
for (int i = clients.size() - 1; i >= 0; i--) {
clients.get(i).getWriter().println("服务器：" + message + "(多人发送)");
clients.get(i).getWriter().flush();
}
}
// 服务器线程
class ServerThread extends Thread {
private ServerSocket serverSocket;
private int max;// 人数上限
// 服务器线程的构造方法
public ServerThread(ServerSocket serverSocket, int max) {
this.serverSocket = serverSocket;
this.max = max;
}
public void run() {
while (true) {// 不停的等待客户端的链接
try {
Socket socket = serverSocket.accept();
if (clients.size() == max) {// 如果已达人数上限
BufferedReader r = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
PrintWriter w = new PrintWriter(socket
.getOutputStream());
// 接收客户端的基本用户信息
String inf = r.readLine();
StringTokenizer st = new StringTokenizer(inf, "@");
User user = new User(st.nextToken(), st.nextToken());
// 反馈连接成功信息
w.println("MAX@服务器：对不起，" + user.getName()
+ user.getIp() + "，服务器在线人数已达上限，请稍后尝试连接！");
w.flush();
// 释放资源
r.close();
w.close();
socket.close();
continue;
}
ClientThread client = new ClientThread(socket);
client.start();// 开启对此客户端服务的线程
clients.add(client);
listModel.addElement(client.getUser().getName());// 更新在线列表
contentArea.append(client.getUser().getName()
+ client.getUser().getIp() + "上线!\r\n");
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
// 为一个客户端服务的线程
class ClientThread extends Thread {
private Socket socket;
private BufferedReader reader;
private PrintWriter writer;
private User user;
public BufferedReader getReader() {
return reader;
}
public PrintWriter getWriter() {
return writer;
}
public User getUser() {
return user;
}
// 客户端线程的构造方法
public ClientThread(Socket socket) {
try {
this.socket = socket;
reader = new BufferedReader(new InputStreamReader(socket
.getInputStream()));
writer = new PrintWriter(socket.getOutputStream());
// 接收客户端的基本用户信息
String inf = reader.readLine();
StringTokenizer st = new StringTokenizer(inf, "@");
user = new User(st.nextToken(), st.nextToken());
// 反馈连接成功信息
writer.println(user.getName() + user.getIp() + "与服务器连接成功!");
writer.flush();
// 反馈当前在线用户信息
if (clients.size() > 0) {
String temp = "";
for (int i = clients.size() - 1; i >= 0; i--) {
temp += (clients.get(i).getUser().getName() + "/" + clients
.get(i).getUser().getIp())
+ "@";
}
writer.println("USERLIST@" + clients.size() + "@" + temp);
writer.flush();
}
// 向所有在线用户发送该用户上线命令
for (int i = clients.size() - 1; i >= 0; i--) {
clients.get(i).getWriter().println(
"ADD@" + user.getName() + user.getIp());
clients.get(i).getWriter().flush();
}
} catch (IOException e) {
e.printStackTrace();
}
}
@SuppressWarnings("deprecation")
public void run() {// 不断接收客户端的消息，进行处理。
String message = null;
while (true) {
try {
message = reader.readLine();// 接收客户端消息
if (message.equals("CLOSE"))// 下线命令
{
contentArea.append(this.getUser().getName()
+ this.getUser().getIp() + "下线!\r\n");
// 断开连接释放资源
reader.close();
writer.close();
socket.close();
// 向所有在线用户发送该用户的下线命令
for (int i = clients.size() - 1; i >= 0; i--) {
clients.get(i).getWriter().println(
"DELETE@" + user.getName());
clients.get(i).getWriter().flush();
}
listModel.removeElement(user.getName());// 更新在线列表
// 删除此条客户端服务线程
for (int i = clients.size() - 1; i >= 0; i--) {
if (clients.get(i).getUser() == user) {
ClientThread temp = clients.get(i);
clients.remove(i);// 删除此用户的服务线程
temp.stop();// 停止这条服务线程
return;
}
}
} else {
dispatcherMessage(message);// 转发消息
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
// 转发消息
public void dispatcherMessage(String message) {
StringTokenizer stringTokenizer = new StringTokenizer(message, "@");
String source = stringTokenizer.nextToken();
String owner = stringTokenizer.nextToken();
String content = stringTokenizer.nextToken();
message = source + "说：" + content;
contentArea.append(message + "\r\n");
if (owner.equals("ALL")) {// 群发
for (int i = clients.size() - 1; i >= 0; i--) {
clients.get(i).getWriter().println(message + "(多人发送)");
clients.get(i).getWriter().flush();
}
}
}
}
} 
