如何使用 swing GUI (Netbeans) 根据 Java 中的登录用户存储和检索数据库信息

Question

I'm pretty new to Java. I'm using Swing and Netbeans on MySQL DB. I am working on a desktop application that allows users to make orders for products. The user have to sign in to order. How do I save the order information for each user after they have logged in. My login code is as shown.

Database connection (dbconnect.java)

package dbconnect;

import java.sql.Connection;
import java.sql.DriverManager;
import javax.swing.JOptionPane;

/**
 *
 * @author Nipun Senarath
 */
public class dbconnect {
    
     public static Connection connect()
    {
        Connection sos = null;
        
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            sos = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/restaurant","root","");
        } catch (Exception e) 
        {
            JOptionPane.showMessageDialog(null, e);
        }
        return sos;
    }

    public static Connection Connect() {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

The login page PatronLogin.java

package patron.auth;


import dbconnect.dbconnect;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import patron.main.MainClass;


public class PatronLogin extends javax.swing.JFrame {
    
    public PatronLogin() {
        initComponents();
    }

 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here: Login button
        String uname = jTextField1.getText();
        String pword = jPasswordField1.getText();
        
        if (uname.equals("")||pword.equals("")) {
            JOptionPane.showMessageDialog(rootPane, "Some fields are empty", "Error", 1);
        } else {
            try {
                Connection con = dbconnect.connect();
                PreparedStatement pst = con.prepareStatement("select * from patron where username=? and password=?");
                pst.setString(1, uname);
                pst.setString(2, pword);
                ResultSet rs = pst.executeQuery();
                                
                if (rs.next()) {
                    MainClass pt = new MainClass();
                    pt.setVisible(true);
                    dispose();
                } else {
                    JOptionPane.showMessageDialog(rootPane, "Username or Password do not match record", "Login error", 1);
                } 
            } catch (Exception ex) {
                System.out.println(""+ex);
            }
        }
    }        

    public static void main(String args[]) { 
      /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                PatronLogin ln = new PatronLogin();
                ln.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                ln.setVisible(true);
            }
        });
    }              

Then the user account page

package patron.main;

import patron.event.EventMenuSelected;
import patron.form.Form_1;
import patron.form.Form_4;
import patron.form.Form_3;
import patron.form.Form_2;
import patron.form.Form_Home;
import java.awt.Color;
import javax.swing.JComponent;

public class MainClass extends javax.swing.JFrame {

    /**
     * Creates new form MainClass
     */
    private Form_Home home;
    private Form_1 form1;
    private Form_2 form2;
    public static Form_3 form3;
    private Form_4 form4;

    public MainClass() {
        initComponents();
        setBackground(new Color(0, 0, 0, 0));
        home = new Form_Home();
        form1 = new Form_1();
        form2 = new Form_2();
        form3 = new Form_3();
        form4 = new Form_4();
        menu.initMoving(MainClass.this);
        menu.addEventMenuSelected(new EventMenuSelected() {
            @Override
            public void selected(int index) {
                if (index == 0) {
                    setForm(home);
                } else if (index == 1) {
                    setForm(form1);
                } else if (index == 2) {
                    setForm(form2);
                } else if (index == 3) {
                    setForm(form3);
                } else if (index == 4) {
                    setForm(form4);
                }
            }
        });
        //  set when system open start with home form
        setForm(new Form_Home());
    }

    public void setForm(JComponent com) {
        mainPanel.removeAll();
        mainPanel.add(com);
        mainPanel.repaint();
        mainPanel.revalidate();
    }
public static void main(String args[]) {      

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MainClass().setVisible(true);
            }
        });
    }

I want to insert an order into the order table with order_id, item, price, and patron_id for the logged in user, so I can be able to retieve it in another table showing the particular user's order history, how do I achieve that. Same goes for other patrons...

Answer 1

There's a lot of work to do, but you can "offload" a lot of that. ;-)

If your desktop-application is a "single-user" application you can create a "Singleton" object to store the current logged user.

That object will represent a "Session", that will be built after a successful login and it will contain the logged user (aka Principal).

There'are various points where you can improve:

• security: password are stored in plain text, it would be better to use an hash function for that -- https://www.baeldung.com/java-password-hashing
• logic and db code in UI: mixing all the code together will make it very harder to handle it and fix it (believe me). Again, following an Object-Oriented approach is better to model with something like:

interface Products {

  List<Product> listAll();

} 

interface Orders {
  void save(Order order)
}

The implementation of that interfaces will interact with the db, returning the data to the UI and doing the actions started from the user.

• db connections handling: obtaining a db connection takes a lot of time, for this reason exists Connection Pools see - https://github.com/brettwooldridge/HikariCP

• db interaction way: instead of plain jdbc you're using see -- https://www.marcobehler.com/guides/java-databases

• TIPS: Nebeans historically could create interface that interact with standard DB interaction ways (ie JPA) -- https:/.netbeans.apache.org/tutorials/74/nbm-crud.html