((1)创建t_users表,字段为id、name、password.email、birthday; (2)创建User类,属性与数据库的七users表中字段一一对应,用于封装数据; 3)使用JDBC相关接口和类实现数据库中数据的查询; (4)创建Servlet程

序实现以下功能：
- 注册：将用户提交的信息插入到t_users表中；
- 登录：根据用户输入的用户名和密码查询t_users表中是否存在对应的记录；
- 修改密码：更新t_users表中对应用户的密码字段；
- 查询用户信息：根据用户输入的用户名查询t_users表中对应的记录，并返回给前端页面。

1. 创建t_users表，字段为id、name、password、email、birthday

CREATE TABLE t_users (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(100) NOT NULL,
  password VARCHAR(100) NOT NULL,
  email VARCHAR(100) NOT NULL,
  birthday DATE NOT NULL
);

2. 创建User类，属性与数据库的t_users表中字段一一对应，用于封装数据

public class User {
    private int id;
    private String name;
    private String password;
    private String email;
    private Date birthday;
    
    // 构造方法、getters、setters
}

3. 使用JDBC相关接口和类实现数据库中数据的查询

public class UserDao {
    private Connection conn;

    public UserDao() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/db";
            String user = "root";
            String password = "root";
            conn = DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 根据用户名和密码查询用户信息
    public User findUser(String name, String password) {
        User user = null;
        try {
            String sql = "SELECT * FROM t_users WHERE name=? AND password=?";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, name);
            pstmt.setString(2, password);
            ResultSet rs = pstmt.executeQuery();
            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setPassword(rs.getString("password"));
                user.setEmail(rs.getString("email"));
                user.setBirthday(rs.getDate("birthday"));
            }
            rs.close();
            pstmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return user;
    }

    // 将用户信息插入到t_users表中
    public void addUser(User user) {
        try {
            String sql = "INSERT INTO t_users(name, password, email, birthday) VALUES(?, ?, ?, ?)";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getName());
            pstmt.setString(2, user.getPassword());
            pstmt.setString(3, user.getEmail());
            pstmt.setDate(4, user.getBirthday());
            pstmt.executeUpdate();
            pstmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 根据用户名查询用户信息
    public User findUserByName(String name) {
        User user = null;
        try {
            String sql = "SELECT * FROM t_users WHERE name=?";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, name);
            ResultSet rs = pstmt.executeQuery();
            if (rs.next()) {
                user = new User();
                user.setId(rs.getInt("id"));
                user.setName(rs.getString("name"));
                user.setPassword(rs.getString("password"));
                user.setEmail(rs.getString("email"));
                user.setBirthday(rs.getDate("birthday"));
            }
            rs.close();
            pstmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return user;
    }

    // 更新用户密码
    public void updatePassword(User user) {
        try {
            String sql = "UPDATE t_users SET password=? WHERE name=?";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, user.getPassword());
            pstmt.setString(2, user.getName());
            pstmt.executeUpdate();
            pstmt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void close() {
        try {
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4. 创建Servlet程序实现以下功能：
- 注册：将用户提交的信息插入到t_users表中；
- 登录：根据用户输入的用户名和密码查询t_users表中是否存在对应的记录；
- 修改密码：更新t_users表中对应用户的密码字段；
- 查询用户信息：根据用户输入的用户名查询t_users表中对应的记录，并返回给前端页面。

public class UserServlet extends HttpServlet {
    private UserDao userDao = new UserDao();

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String action = request.getParameter("action");
        if (action.equals("register")) {
            register(request, response);
        } else if (action.equals("login")) {
            login(request, response);
        } else if (action.equals("changepassword")) {
            changePassword(request, response);
        } else if (action.equals("finduser")) {
            findUser(request, response);
        }
    }

    // 注册
    private void register(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String name = request.getParameter("name");
        String password = request.getParameter("password");
        String email = request.getParameter("email");
        String birthday = request.getParameter("birthday");

        User user = new User();
        user.setName(name);
        user.setPassword(password);
        user.setEmail(email);
        user.setBirthday(Date.valueOf(birthday));

        userDao.addUser(user);

        response.sendRedirect("success.jsp");
    }

    // 登录
    private void login(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String name = request.getParameter("name");
        String password = request.getParameter("password");

        User user = userDao.findUser(name, password);
        if (user != null) {
            HttpSession session = request.getSession();
            session.setAttribute("user", user);
            response.sendRedirect("main.jsp");
        } else {
            response.sendRedirect("fail.jsp");
        }
    }

    // 修改密码
    private void changePassword(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String name = request.getParameter("name");
        String password = request.getParameter("password");

        User user = new User();
        user.setName(name);
        user.setPassword(password);

        userDao.updatePassword(user);

        response.sendRedirect("success.jsp");
    }

    // 查询用户信息
    private void findUser(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String name = request.getParameter("name");

        User user = userDao.findUserByName(name);

        request.setAttribute("user", user);
        request.getRequestDispatcher("userinfo.jsp").forward(request, response);
    }

    public void destroy() {
        userDao.close();
    }
}