1. Password Validation Requirements

1.1 Client-Side (JavaScript in login.jsp)

1.2. Server-Side (Servlet)

Resolve requirements

Create a Password Validator

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package utils;

import java.util.regex.Pattern;

public class PasswordValidator {

    // Regex rule: At least 8 chars, one upper, one lower, one digit, one special char
    private static final String PASSWORD_PATTERN =
            "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[@#$%^&*!?])[A-Za-z\\d@#$%^&*!?]{8,}$";

    private static final Pattern pattern = Pattern.compile(PASSWORD_PATTERN);

    /**
     * Validate password strength
     * @param password the password input
     * @return true if valid, false otherwise
     */
    public static boolean isValid(String password) {
        if (password == null || password.trim().isEmpty()) {
            return false;
        }
        return pattern.matcher(password).matches();
    }

    /**
     * Validate only basic length (if you want a simpler rule)
     */
    public static boolean isMinLength(String password, int length) {
        return password != null && password.length() >= length;
    }
}

Note: Regular expression (Regex)

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    ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@#$%^&*!?])[A-Za-z\d@#$%^&*!?]{8,}$

This is a Java-style regex (works with String.matches() or Pattern.compile()), commonly used for password validation. It ensures:

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    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        // Validate password format first
        // if (!PasswordValidator.isMinLength(password, 8)) {
        //     request.setAttribute("loginError", "Password must be at least 8 characters long.");

        //     request.setAttribute("contentPage", "login_form_content.jsp");
        //     request.getRequestDispatcher("views/pages/login.jsp").forward(request, response);
        //     return;
        // }
        

        if (!PasswordValidator.isValid(password)) {
            request.setAttribute("loginError", "Password must contain uppercase, lowercase, number, special char, and be at least 8 characters.");
            
            request.setAttribute("contentPage", "login_form_content.jsp");
            request.getRequestDispatcher("views/pages/login.jsp").forward(request, response);
            return;
        }
        
        // Authenticate with database
        String uName = userDAO.CheckUser(username, password);

        if (user != null) {
            HttpSession session = request.getSession();
            session.setAttribute("user", user);
            response.sendRedirect("home");
        } else {
            request.setAttribute("loginError", "Invalid username or password.");
            request.getRequestDispatcher("views/pages/login.jsp").forward(request, response);
        }
    }


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    <!-- ... -->
    
    <button type="submit" class="btn btn-primary">Login</button>
    
    <p style="color:red;"><%= request.getAttribute("loginError") != null ? request.getAttribute("loginError") : "" %></p>
    
    <!-- ... -->

Update password of Users

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    UPDATE Users
    SET Password = '123456x@X'
    WHERE Username = 'admin';