Java用户注册登录实现教程

CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(50) UNIQUE NOT NULL,
    password VARCHAR(255) NOT NULL,
    email VARCHAR(100),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    String email = request.getParameter("email");

    // 简单校验
    if (username == null || password == null || username.isEmpty() || password.isEmpty()) {
        response.sendRedirect("register.jsp?error=用户名或密码不能为空");
        return;
    }

    // 检查用户是否已存在
    UserDAO userDAO = new UserDAO();
    if (userDAO.userExists(username)) {
        response.sendRedirect("register.jsp?error=用户名已存在");
        return;
    }

    // 加密密码并保存
    String hashedPassword = BCrypt.hashpw(password, BCrypt.gensalt());
    User user = new User(0, username, hashedPassword, email, null);
    userDAO.save(user);

    response.sendRedirect("login.jsp?success=注册成功，请登录");
}

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");

    UserDAO userDAO = new UserDAO();
    User user = userDAO.findByUsername(username);

    if (user != null && BCrypt.checkpw(password, user.getPassword())) {
        // 创建会话
        HttpSession session = request.getSession();
        session.setAttribute("user", user);
        response.sendRedirect("dashboard.jsp");
    } else {
        response.sendRedirect("login.jsp?error=用户名或密码错误");
    }
}