navicat

好的，下面是一个使用MySQL数据库和Servlet的基本登录注册代码示例：

1. 创建一个名为`User`的JavaBean类，包含以下属性和方法：

public class User {
    private String username;
    private String password;

    // 构造方法
    public User() {}

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    // getters 和 setters
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

2. 创建一个名为`DBUtil`的数据库工具类，用于连接数据库和执行SQL语句：

public class DBUtil {
    private static final String URL = "jdbc:mysql://localhost:3306/test?useSSL=false";
    private static final String USER = "root";
    private static final String PASSWORD = "123456";

    // 获取数据库连接
    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    // 执行查询操作
    public static ResultSet executeQuery(String sql, Object... params) {
        Connection conn = getConnection();
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            pstmt = conn.prepareStatement(sql);
            for (int i = 0; i < params.length; i++) {
                pstmt.setObject(i + 1, params[i]);
            }
            rs = pstmt.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return rs;
    }

    // 执行更新操作
    public static int executeUpdate(String sql, Object... params) {
        Connection conn = getConnection();
        PreparedStatement pstmt = null;
        int result = 0;
        try {
            pstmt = conn.prepareStatement(sql);
            for (int i = 0; i < params.length; i++) {
                pstmt.setObject(i + 1, params[i]);
            }
            result = pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close(conn, pstmt, null);
        }
        return result;
    }

    // 关闭资源
    public static void close(Connection conn, Statement stmt, ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

3. 创建一个名为`UserDao`的数据访问对象类，用于对用户表进行CRUD操作：

public class UserDao {
    // 添加用户
    public boolean addUser(User user) {
        String sql = "INSERT INTO user(username, password) VALUES(?, ?)";
        int result = DBUtil.executeUpdate(sql, user.getUsername(), user.getPassword());
        return result > 0;
    }

    // 根据用户名查询用户
    public User getUserByUsername(String username) {
        User user = null;
        String sql = "SELECT * FROM user WHERE username=?";
        ResultSet rs = DBUtil.executeQuery(sql, username);
        try {
            if (rs.next()) {
                user = new User();
                user.setUsername(rs.getString("username"));
                user.setPassword(rs.getString("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(null, null, rs);
        }
        return user;
    }
}

4. 创建一个名为`LoginServlet`的Servlet类，用于处理用户登录请求：

@WebServlet("/login")
public class LoginServlet extends HttpServlet {
    private UserDao userDao;

    @Override
    public void init() throws ServletException {
        userDao = new UserDao();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取表单参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 根据用户名查询用户
        User user = userDao.getUserByUsername(username);

        // 验证用户信息
        if (user != null && user.getPassword().equals(password)) {
            // 登录成功，将用户信息保存到Session中
            HttpSession session = request.getSession();
            session.setAttribute("user", user);

            // 跳转到首页
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        } else {
            // 登录失败，返回错误信息
            request.setAttribute("error", "用户名或密码错误！");
            request.getRequestDispatcher("/login.jsp").forward(request, response);
        }
    }
}

5. 创建一个名为`RegisterServlet`的Servlet类，用于处理用户注册请求：

@WebServlet("/register")
public class RegisterServlet extends HttpServlet {
    private UserDao userDao;

    @Override
    public void init() throws ServletException {
        userDao = new UserDao();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取表单参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 封装用户对象
        User user = new User(username, password);

        // 添加用户
        boolean result = userDao.addUser(user);

        // 返回结果
        if (result) {
            request.setAttribute("message", "注册成功，请登录！");
            request.getRequestDispatcher("/login.jsp").forward(request, response);
        } else {
            request.setAttribute("error", "注册失败，请重试！");
            request.getRequestDispatcher("/register.jsp").forward(request, response);
        }
    }
}

以上就是一个基本的登录注册代码示例，您可以根据自己的需要进行修改和完善。