使用Swing应用程序时无法提交数据，否则将正常工作

Question

当我在main函数中编写PreparedStatement时，它可以完美地工作并提交数据，但是当我在actionPerformed函数中编写时，它不起作用，为什么？ 我认为我没有做错任何事情。

import javax.swing.*;
import java.awt.event.*;
import java.sql.*;

public class EnterData {

    static void insertData(int rn, String fn, String ln) throws ClassNotFoundException, SQLException {    
        Class.forName("com.mysql.jdbc.Driver");
        try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/studentinfo","root","12345")) {
            String query = "insert into student (rollno, fname, lname)" + " values (?, ?, ?)";
            PreparedStatement preparedStmt = conn.prepareStatement(query);
            preparedStmt.setInt (1, rn);
            preparedStmt.setString (2, fn);
            preparedStmt.setString (3, ln);
            preparedStmt.execute();
        }
    }

    public static void main(String[] args) {
        JFrame mainFrame = new JFrame("Submit Information");
        mainFrame.setSize(400, 300);
        mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainFrame.setLocationRelativeTo(null);
        mainFrame.setLayout(null);

        JLabel heading = new JLabel("Enter Data");
        heading.setBounds(150, 10, 100, 20);
        mainFrame.add(heading);

        JLabel rollnoLabel = new JLabel("Roll Number");
        rollnoLabel.setBounds(70, 60, 100, 20);
        mainFrame.add(rollnoLabel);
        JTextField rollno = new JTextField();
        rollno.setBounds(220, 60, 100, 20);
        mainFrame.add(rollno);

        // Taking First Name
        JLabel name1 = new JLabel("First Name");
        name1.setBounds(70, 110, 100, 20);
        mainFrame.add(name1);
        JTextField fname = new JTextField();
        fname.setBounds(220, 110, 100, 20);
        mainFrame.add(fname);

        // Taking Last Name
        JLabel name2 = new JLabel("Last Name");
        name2.setBounds(70, 160, 100, 20);
        mainFrame.add(name2);
        JTextField lname = new JTextField();
        lname.setBounds(220, 160, 100, 20);
        mainFrame.add(lname);

        // Submit and Reset Button
        JButton submit = new JButton("Submit");
        submit.setBounds(70, 220, 100, 20);
        mainFrame.add(submit);
        JButton reset = new JButton("Reset");
        reset.setBounds(220, 220, 100, 20);
        mainFrame.add(reset);

        // Frame Visibility
        mainFrame.setVisible(true);

        submit.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    int rn = Integer.parseInt(rollno.getText());
                    String fn = fname.getText();
                    String ln = lname.getText();

                    insertData(rn, fn, ln);

                    JOptionPane.showMessageDialog(null, "Submitted Successfully...!!!", "Submission Prompt", JOptionPane.PLAIN_MESSAGE);
                } catch (Exception ex) {
                    System.err.println("Got an exception!");
                    System.err.println(ex.getMessage());
                }
            }
        });
    }
}

我已经尝试过了，并且效果很好，但是当我将这些语句放入actionPerformed函数中时，它们将不起作用。

import java.sql.*;

public class DatabaseTest {

    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/studentinfo","root","12345");

            String query = "insert into student (rollno, fname, lname)" + " values (?, ?, ?)";

            PreparedStatement preparedStmt = conn.prepareStatement(query);
            preparedStmt.setInt (1, 6505);
            preparedStmt.setString (2, "Prince");
            preparedStmt.setString (3, "Saini");

            preparedStmt.execute();
            conn.close();
        } catch (Exception e) {
            System.err.println("Got an exception!");
            System.err.println(e.getMessage());
        }
    }
}