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登录功能实现

1. 登录页面设置

登录页面应设置为 login.jsp，并在欢迎页中指定登录页面或通过 index.jsp 转发至 login.jsp。以下是通过 index.jsp 实现的转发方式：

2. 数据库访问接口

定义 LoginDao 接口，用于获取用户登录信息：

public interface LoginDao {
    User getLogin(String userCode) throws SQLException;
}

3. 数据库访问实现类

实现 LoginDao 接口的 LoginDaoImpl 类：

public class LoginDaoImpl implements LoginDao {
    @Override
    public User getLogin(String uCode) throws SQLException {
        Connection conn = BaseDao.getConn();
        if (conn != null) {
            try {
                PreparedStatement preparedStatement = conn.prepareStatement(
                    "SELECT * FROM smbms_user WHERE userCode = ?");
                preparedStatement.setString(1, uCode);
                ResultSet resultSet = BaseDao.executeQ(conn, preparedStatement, null, null);
                if (resultSet.next()) {
                    User user = new User();
                    user.setId(resultSet.getInt("id"));
                    user.setUserCode(resultSet.getString("userCode"));
                    user.setUserName(resultSet.getString("userName"));
                    user.setUserPassword(resultSet.getString("userPassword"));
                    // 其他字段获取和赋值
                    return user;
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
            BaseDao.close(conn, preparedStatement, null);
        }
        return null;
    }
}

4. 业务逻辑接口

定义 LoginService 接口，用于处理登录业务：

public interface LoginService {
    User login(String uCode, String uPassword) throws SQLException;
}

5. 业务逻辑实现类

实现 LoginService 接口的 LoginServiceImpl 类：

public class LoginServiceImpl implements LoginService {
    @Override
    public User login(String uCode, String uPassword) throws SQLException {
        LoginDao loginDao = new LoginDaoImpl();
        User user = loginDao.getLogin(uCode);
        return user;
    }
}

6. 登录Servlet实现

创建 LoginServlet 类，处理登录请求：

@WebServlet("/login.do")
public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        String userCode = req.getParameter("userCode");
        String password = req.getParameter("userPassword");
        LoginService loginService = new LoginServiceImpl();
        try {
            User user = loginService.login(userCode, password);
            if (user != null) {
                HttpSession session = req.getSession();
                session.setAttribute(Constants.USER_SESSION, user);
                resp.sendRedirect("frame.jsp");
            } else {
                req.setAttribute("error", "用户名或密码错误");
                req.getRequestDispatcher("login.jsp").forward(req, resp);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

7. 登出功能实现

创建 LogoutServlet 类，处理注销操作：

@WebServlet("/user/exit.do")
public class LogoutServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
        HttpSession session = req.getSession();
        session.removeAttribute(Constants.USER_SESSION);
        resp.sendRedirect("/login.jsp");
    }
}

8. 登录拦截优化

创建 SysFilter 类，实现登录拦截：

@WebFilter("/jsp/*")
public class SysFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 初始化逻辑可根据需求添加
    }
    @Override
    public void doFilter(
        ServletRequest servletRequest,
        ServletResponse servletResponse,
        FilterChain filterChain)
        throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpSession session = request.getSession();
        User user_sess = (User) session.getAttribute(Constants.USER_SESSION);
        if (user_sess == null) {
            request.getRequestDispatcher("/error.jsp").forward(request, response);
        } else {
            filterChain.doFilter(servletRequest, servletResponse);
        }
    }
    @Override
    public void destroy() {
        // 销毁逻辑可根据需求添加
    }
}

总结

以上实现完整地完成了登录功能的开发，涵盖了页面转发、数据库访问、业务逻辑处理以及前后端的整合。通过拦截器优化，确保未登录用户无法访问核心功能，进一步提升了系统安全性。

转载地址：http://ulgh.baihongyu.com/