Let’s create a CRUD application with a MySQL database and user management. This will include connecting to a MySQL database, managing user login, and performing CRUD operations on user data.
Project Setup
- IDE: Use an Integrated Development Environment (IDE) like IntelliJ IDEA, Eclipse, or NetBeans.
- JDK: Ensure you have the Java Development Kit (JDK) installed.
- MySQL: Set up a MySQL server and create a database.
- JDBC Driver: Download and add the MySQL JDBC driver to your project.
MySQL Database Setup
- Create a database named
crud_db. - Create a table named
userswith the following structure:
CREATE DATABASE crud_db;
USE crud_db;
CREATE TABLE users (
id INT AUTO_INCREMENT PRIMARY KEY,
username VARCHAR(50) NOT NULL UNIQUE,
password VARCHAR(50) NOT NULL,
email VARCHAR(100)
);
Step-by-Step Guide with Code and Comments
1. Create the Main Class
This is the entry point of your application.
package com.crudapp;
public class Main {
public static void main(String[] args) {
// Start the application
LoginFrame loginFrame = new LoginFrame();
loginFrame.setVisible(true);
}
}
2. Create the Database Connection Class
This class handles the connection to the MySQL database.
package com.crudapp;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DatabaseConnection {
private static final String URL = "jdbc:mysql://localhost:3306/crud_db";
private static final String USER = "root"; // replace with your MySQL username
private static final String PASSWORD = ""; // replace with your MySQL password
// Method to get a connection to the database
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(URL, USER, PASSWORD);
}
}
Explanation:
URL,USER,PASSWORD: Constants for the database connection details.public static Connection getConnection() throws SQLException: Method to establish and return a database connection.
3. Create the User Management Class
This class handles user-related operations.
package com.crudapp;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class UserManager {
// Method to add a new user
public static boolean addUser(String username, String password, String email) {
String query = "INSERT INTO users (username, password, email) VALUES (?, ?, ?)";
try (Connection conn = DatabaseConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(query)) {
stmt.setString(1, username);
stmt.setString(2, password);
stmt.setString(3, email);
int rows = stmt.executeUpdate();
return rows > 0;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
// Method to verify user login
public static boolean verifyUser(String username, String password) {
String query = "SELECT * FROM users WHERE username = ? AND password = ?";
try (Connection conn = DatabaseConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(query)) {
stmt.setString(1, username);
stmt.setString(2, password);
ResultSet rs = stmt.executeQuery();
return rs.next();
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
// Method to read all users
public static ResultSet getAllUsers() {
String query = "SELECT * FROM users";
try {
Connection conn = DatabaseConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(query);
return stmt.executeQuery();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
}
// Method to update a user's email
public static boolean updateUserEmail(String username, String newEmail) {
String query = "UPDATE users SET email = ? WHERE username = ?";
try (Connection conn = DatabaseConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(query)) {
stmt.setString(1, newEmail);
stmt.setString(2, username);
int rows = stmt.executeUpdate();
return rows > 0;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
// Method to delete a user
public static boolean deleteUser(String username) {
String query = "DELETE FROM users WHERE username = ?";
try (Connection conn = DatabaseConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(query)) {
stmt.setString(1, username);
int rows = stmt.executeUpdate();
return rows > 0;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
}
Explanation:
addUser: Adds a new user to the database.verifyUser: Verifies user login credentials.getAllUsers: Retrieves all users from the database.updateUserEmail: Updates the email of a user.deleteUser: Deletes a user from the database.
4. Create the Login Frame Class
This class handles the user login interface.
package com.crudapp;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class LoginFrame extends JFrame {
private JPanel panel;
private JLabel user
package com.crudapp;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
// Class for the login frame
public class LoginFrame extends JFrame {
private JPanel panel;
private JLabel userLabel;
private JTextField userTextField;
private JLabel passwordLabel;
private JPasswordField passwordField;
private JButton loginButton;
private JButton registerButton;
private JLabel messageLabel;
// Constructor to set up the login frame
public LoginFrame() {
// Set the title of the frame
setTitle("Login");
// Initialize the components
panel = new JPanel();
userLabel = new JLabel("Username:");
userTextField = new JTextField(20);
passwordLabel = new JLabel("Password:");
passwordField = new JPasswordField(20);
loginButton = new JButton("Login");
registerButton = new JButton("Register");
messageLabel = new JLabel();
// Add components to the panel
panel.add(userLabel);
panel.add(userTextField);
panel.add(passwordLabel);
panel.add(passwordField);
panel.add(loginButton);
panel.add(registerButton);
panel.add(messageLabel);
// Add the panel to the frame
add(panel);
// Set the size of the frame
setSize(300, 200);
// Define what happens when the frame is closed
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Add action listeners for buttons
loginButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
login();
}
});
registerButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
register();
}
});
}
// Method to handle login action
private void login() {
String username = userTextField.getText();
String password = new String(passwordField.getPassword());
if (UserManager.verifyUser(username, password)) {
messageLabel.setText("Login successful");
AppFrame appFrame = new AppFrame(username);
appFrame.setVisible(true);
dispose(); // Close the login frame
} else {
messageLabel.setText("Invalid username or password");
}
}
// Method to handle registration action
private void register() {
String username = userTextField.getText();
String password = new String(passwordField.getPassword());
if (UserManager.addUser(username, password, "")) {
messageLabel.setText("User registered successfully");
} else {
messageLabel.setText("User registration failed");
}
}
}
Explanation:
LoginFrame: A class that creates the login window with components for username, password, and buttons for login and registration.- Action Listeners: Handle the login and registration actions by verifying the user or adding a new user.
5. Create the AppFrame Class
This class sets up the main frame of the GUI after login.
package com.crudapp;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.ResultSet;
import java.sql.SQLException;
public class AppFrame extends JFrame {
private JPanel panel;
private JLabel emailLabel;
private JTextField emailTextField;
private JButton updateButton;
private JButton deleteButton;
private JTextArea textArea;
private String username;
// Constructor to set up the frame
public AppFrame(String username) {
this.username = username;
// Set the title of the frame
setTitle("User Management");
// Initialize the components
panel = new JPanel();
emailLabel = new JLabel("New Email:");
emailTextField = new JTextField(20);
updateButton = new JButton("Update Email");
deleteButton = new JButton("Delete User");
textArea = new JTextArea(10, 30);
// Add components to the panel
panel.add(emailLabel);
panel.add(emailTextField);
panel.add(updateButton);
panel.add(deleteButton);
panel.add(new JScrollPane(textArea));
// Add the panel to the frame
add(panel);
// Set the size of the frame
setSize(400, 300);
// Define what happens when the frame is closed
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Load current user data
loadUserData();
// Add action listeners for buttons
updateButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
updateEmail();
}
});
deleteButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
deleteUser();
}
});
}
// Method to load current user data
private void loadUserData() {
textArea.append("Current Users:\n");
ResultSet rs = UserManager.getAllUsers();
try {
while (rs != null && rs.next()) {
String user = rs.getString("username");
String email = rs.getString("email");
textArea.append(user + " - " + email + "\n");
}
} catch (SQLException e) {
e.printStackTrace();
}
}
// Method to update user's email
private void updateEmail() {
String newEmail = emailTextField.getText();
if (UserManager.updateUserEmail(username, newEmail)) {
textArea.append("Updated email to: " + newEmail + "\n");
emailTextField.setText("");
} else {
textArea.append("Failed to update email\n");
}
}
// Method to delete user
private void deleteUser() {
if (UserManager.deleteUser(username)) {
textArea.append("Deleted user: " + username + "\n");
dispose(); // Close the app frame
} else {
textArea.append("Failed to delete user\n");
}
}
}
Explanation:
AppFrame: A class that creates the main application window for user management after login.- Constructor: Sets up the GUI components and loads current user data.
loadUserData: Fetches and displays all users from the database.updateEmail: Updates the email address of the logged-in user.deleteUser: Deletes the logged-in user from the database.
Running the Application
- Run the
Mainclass. - The login window will appear. Use it to log in or register a new user.
- Upon successful login, the main application window will appear, allowing you to manage user data.
This guide provides a simple CRUD application with MySQL integration and user management, along with detailed explanations and comments to help beginners understand each step and component.
