2.利用套接字、多线程、GUI和数据库，参考[例13-简单的C-S结构程序]或[例13-基于C-S结构的学生基本信息管理系统],实现一个C/S结构的查询服务器上数据库表的程序，可以按学号查询、按姓名查询。[50]写出Java示例代码

以下是一个简单的Java示例代码，实现了一个C/S结构的查询服务器上数据库表的程序，可以按学号查询、按姓名查询。代码使用了套接字、多线程、GUI和数据库技术。

服务器端代码：

import java.io.*;
import java.net.*;
import java.sql.*;

public class Server {

    private static final int PORT = 54321;

    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(PORT);
            System.out.println("Server started...");

            while (true) {
                Socket clientSocket = serverSocket.accept();
                System.out.println("Client connected: " + clientSocket);

                Thread clientThread = new Thread(new ClientHandler(clientSocket));
                clientThread.start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static class ClientHandler implements Runnable {
        private Socket clientSocket;

        public ClientHandler(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }

        public void run() {
            try {
                BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);

                String request = in.readLine();
                System.out.println("Received request: " + request);

                Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password");
                Statement statement = connection.createStatement();

                if (request.equals("QUERY_BY_ID")) {
                    String id = in.readLine();
                    ResultSet resultSet = statement.executeQuery("SELECT * FROM students WHERE id = " + id);
                    while (resultSet.next()) {
                        String name = resultSet.getString("name");
                        int age = resultSet.getInt("age");
                        out.println(name + "\t" + age);
                    }
                } else if (request.equals("QUERY_BY_NAME")) {
                    String name = in.readLine();
                    ResultSet resultSet = statement.executeQuery("SELECT * FROM students WHERE name = '" + name + "'");
                    while (resultSet.next()) {
                        String id = resultSet.getString("id");
                        int age = resultSet.getInt("age");
                        out.println(id + "\t" + age);
                    }
                }

                connection.close();
                clientSocket.close();
                System.out.println("Client disconnected: " + clientSocket);
            } catch (IOException | SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端代码：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class Client {

    private static final String SERVER_ADDRESS = "localhost";
    private static final int SERVER_PORT = 54321;

    private JFrame frame;
    private JTextField idTextField;
    private JTextField nameTextField;
    private JTextArea resultTextArea;

    public static void main(String[] args) {
        new Client().start();
    }

    public void start() {
        frame = new JFrame("Student Query");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 300);

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(3, 2));

        JLabel idLabel = new JLabel("ID");
        idTextField = new JTextField();
        JLabel nameLabel = new JLabel("Name");
        nameTextField = new JTextField();

        panel.add(idLabel);
        panel.add(idTextField);
        panel.add(nameLabel);
        panel.add(nameTextField);

        JButton idButton = new JButton("Query by ID");
        idButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                queryById();
            }
        });

        JButton nameButton = new JButton("Query by Name");
        nameButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                queryByName();
            }
        });

        panel.add(idButton);
        panel.add(nameButton);

        frame.add(panel, BorderLayout.NORTH);

        resultTextArea = new JTextArea();
        frame.add(new JScrollPane(resultTextArea), BorderLayout.CENTER);

        frame.setVisible(true);
    }

    private void queryById() {
        try {
            Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT);

            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            out.println("QUERY_BY_ID");
            out.println(idTextField.getText());

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            resultTextArea.setText("");
            String line;
            while ((line = in.readLine()) != null) {
                resultTextArea.append(line + "\n");
            }

            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void queryByName() {
        try {
            Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT);

            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            out.println("QUERY_BY_NAME");
            out.println(nameTextField.getText());

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            resultTextArea.setText("");
            String line;
            while ((line = in.readLine()) != null) {
                resultTextArea.append(line + "\n");
            }

            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

注意：上述代码只是一个示例，需要根据实际情况进行修改和完善。例如，需要根据实际数据库的情况修改连接字符串、用户名和密码；需要添加异常处理和错误提示等等。