How to Connect Login Page to Database in Java?

In Java, there are multiple processes involved in connecting a login page to a database: building the database, establishing the connection, and running SQL queries. Here is a comprehensive how-to that includes all of the Java code.

Database Connection in Java

JDBC (Java Database Connectivity)

Java Database Connectivity, or JDBC, is an API for Java that enables Java programs to communicate with relational databases. It offers a collection of classes and functions for initiating database connections, carrying out SQL queries, and managing the outcomes.Java programs may connect to and communicate with relational databases using a uniform and standardized interface thanks to JDBC (Java Database Connectivity). The Java programming language and other database management systems (DBMS) are connected via JDBC.

In the DatabaseConnector class:

JDBC_URL: Indicates the database connection URL.
The database credentials for authentication are USERNAME and PASSWORD.
Loads the MySQL JDBC driver class using Class.forName("com.mysql.cj.jdbc.Driver").
Driver Manager.createConnection(): Creates a database connection.

Procedure for Authentication

Hashing Passwords

Passwords stored in plain text within a database pose a security concern. Passwords are frequently hashed before being stored. In general, you would compare the hashed values during authentication and hash the password before saving it in the database.

SQL Query for Authentication

The LoginService class performs authentication using a SQL query:

The query checks if a user with the provided username and password exists in the user's table.

Security Considerations

SQL Injection: To guard against SQL injection attacks, the code makes use of prepared statements (PreparedStatement). Prepared statements guard against malicious input by automatically quoting and escaping values.
Safe Password Storage: For increased security in real-world situations, think about utilising more robust password encryption techniques like Argon2 or bcrypt.

Step 1: Set Up the Database

Let's suppose that you are using MySQL as the database for this example. Make a table called "users" with columns for the username and password and a database called "db".

CREATE DATABASE user_db;
USE db;
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255) NOT NULL,
    password VARCHAR(255) NOT NULL
);

Insert a single record in the above table with the following SQL statement:

INSERT INTO users (id, name, password)
VALUES (13, 'Ravi', '1234@asdf');

Step 2: Java Code for Database Connection

Create a Java class named DatabaseConnector to handle the database connection.

import java.sql.*;
public class DatabaseConnector {
    private static final String JDBC_URL = "jdbc:mysql://localhost/user_db";
    private static final String USERNAME = "username";
    private static final String PASSWORD = "password";
    public static Connection connect() throws SQLException {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            return DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
        } catch (ClassNotFoundException e) {
            throw new SQLException("Database driver not found", e);
        }
    }
}

Replace "username" and "password" with your MySQL username and password.

Step 3: Java Code for Login

Now, create a class named LoginService to handle user authentication.

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class LoginService {
    public boolean authenticateUser(String username, String password) {
        String query = "SELECT * FROM users WHERE username =? AND password = ?";
        try (Connection connection = DatabaseConnector.connect();
             PreparedStatement preparedStatement = connection.prepareStatement(query)) {
            preparedStatement.setString(1, username);
            preparedStatement.setString(2, password);
            try (ResultSet resultSet = preparedStatement.executeQuery()) {
                return resultSet.next();
            }
        } catch (SQLException e) {
            e.printStackTrace(); 
            return false;
        }
    }
}

Output:

How to Connect Login Page to Database in Java

If the user credentials are present in the database, we can log into the webpage or else it will show Invalid Credentials.

Step 4: Create a Simple Login Page

Now, create a simple Java Swing-based login page.

LoginPage.java

import javax.swing.*;
import java.awt.event.*;
public class LoginPage extends JFrame {
    private JTextField usernameField;
    private JPasswordField passwordField;
    public LoginPage() {
        setTitle("Login Page");
        setSize(400, 350);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));
        usernameField = new JTextField();
        passwordField = new JPasswordField();
        JButton loginButton = new JButton("Login");
        loginButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String username = usernameField.getText();
                String password = new String(passwordField.getPassword());
                LoginService loginService = new LoginService();
                if (loginService.authenticateUser(username, password)) {
                    JOptionPane.showMessageDialog(null, "Login Successful");
                } else {
                    JOptionPane.showMessageDialog(null, "Invalid Credentials");
                }
            }
        });
        add(new JLabel("Username:"));
        add(usernameField);
        add(new JLabel("Password:"));
        add(passwordField);
        add(loginButton);
        setVisible(true);
    }
    public static void main(String[] args) {
        new LoginPage();
    }
}

Output: