[已解决]用session实现免登录

她与晚风 · 发表于 2023-4-30 12:06:27

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本帖最后由她与晚风于 2023-4-30 12:11 编辑

代码如下:
二次免登录页面:

package bj;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.*;

import java.io.IOException;
import java.sql.*;

@WebServlet({"/welcome"})
public class welcomePage extends HttpServlet {
@Override
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      Cookie[] cookies = request.getCookies();
      Connection connection = null;
      PreparedStatement preparedStatement = null;
      ResultSet resultSet = null;
      HttpSession session = request.getSession();
      String sql;
      String username = null;
      String password = null;
      if(cookies != null) {
         for (Cookie cookie : cookies) {
            if ("username".equals(cookie.getName())) {
                  username = cookie.getName();
            }
            if ("password".equals(cookie.getValue())) {
                  password = cookie.getValue();
            }
         }
         if(username !=null && password != null){
            sql = "select * from t_login where username = ? and password = ?";
            System.out.println(username + ": " + password);
            try {
                  Class.forName("com.mysql.cj.jdbc.Driver");
                  connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/myemployees", "root", "123456");
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setString(1,username);
                  preparedStatement.setInt(2, Integer.parseInt(password));
                  resultSet = preparedStatement.executeQuery();
               if(resultSet.next()){
                     System.out.println("登录成功");
                     connection.setAutoCommit(true);
                     session.setAttribute("username",username);
                     response.sendRedirect(request.getContextPath() + "/dept/List");
//可以执行到这里,到好像跳转的不是List页面,又回到了/index.jsp页面
                  }else {
                     System.out.println("登录失败");
                     response.sendRedirect(request.getContextPath() + "/index.jsp");
                  }
            } catch (SQLException e) {
                  throw new RuntimeException(e);
            } catch (ClassNotFoundException e) {
                  throw new RuntimeException(e);
            }

         }else {
            response.sendRedirect(request.getContextPath() + "/index.jsp");
         }
      }

            /*
            */
}
}

最佳答案

月排行榜 / 总排行榜

isdkz

2023-4-30 12:10:26

您的代码已经实现了免登录功能，这里是通过使用Session和Cookie来实现的。当用户登录后，服务器会将用户名和密码存储在Cookie中，然后在需要进行身份验证的页面，通过读取Cookie中的信息来实现自动登录。

代码的逻辑如下：

1. 获取请求中的所有Cookie。
2. 遍历这些Cookie，找到名为"username"和"password"的Cookie。
3. 如果找到了这两个Cookie，从这些Cookie中获取用户名和密码。
4. 使用获取到的用户名和密码查询数据库以验证用户身份。
5. 如果用户身份验证成功，将用户名存储在Session中，并将用户重定向到部门列表页面。
6. 如果身份验证失败，将用户重定向到登录页面。

为了让您的代码更清晰，我对您的代码进行了一些重构和注释：

package bj;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.*;

import java.io.IOException;
import java.sql.*;

@WebServlet({"/welcome"})
public class welcomePage extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies = request.getCookies();
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        HttpSession session = request.getSession();
        String sql;
        String username = null;
        String password = null;

        // 从Cookie中获取用户名和密码
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                if ("username".equals(cookie.getName())) {
                    username = cookie.getValue();
                }
                if ("password".equals(cookie.getName())) {
                    password = cookie.getValue();
                }
            }
        }

        // 如果找到了用户名和密码，验证用户身份
        if (username != null && password != null) {
            sql = "select * from t_login where username = ? and password = ?";
            System.out.println(username + ":    " + password);
            try {
                Class.forName("com.mysql.cj.jdbc.Driver");
                connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/myemployees", "root", "123456");
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1, username);
                preparedStatement.setInt(2, Integer.parseInt(password));
                resultSet = preparedStatement.executeQuery();

                // 如果身份验证成功，将用户名存储在Session中，并重定向到部门列表页面
                if (resultSet.next()) {
                    System.out.println("登录成功");
                    connection.setAutoCommit(true);
                    session.setAttribute("username", username);
                    response.sendRedirect(request.getContextPath() + "/dept/List");
                } else {
                    // 身份验证失败，重定向到登录页面
                    System.out.println("登录失败");
                    response.sendRedirect(request.getContextPath() + "/index.jsp");
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            } catch (ClassNotFoundException e) {
                throw new RuntimeException(e);
            }
        } else {
            // 没有找到用户名和密码，重定向到登录页面
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        }
    }
}

这样，您的代码会更易于阅读和理解。

跳转到最佳答案楼层

她与晚风 · 发表于 2023-4-30 12:07:21

本帖最后由她与晚风于 2023-4-30 12:08 编辑

//Servlet代码主体

package bj;

import MyUtil.DepartmentUser;
import MyUtil.EmoloyeeUser;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.*;

import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;

@WebServlet({"/dept/List","/dept/Delete","/dept/Detail","/dept/Update","/dept/login"})
public class ServletList extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

      Connection connection = null;
      PreparedStatement preparedStatement = null;
      ResultSet resultSet = null;
      String sql;
      try {
         Class.forName("com.mysql.cj.jdbc.Driver");
         connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/myemployees","root","123456");
         if("/dept/List".equals(request.getServletPath())){
            HttpSession session = request.getSession(false);
            ///
            System.out.println(session);
            System.out.println(session.getAttribute("username"));
            ///
            if(session == null || session.getAttribute("username") == null){
                  //
                  System.out.println("执行了吗");
                  //
                  response.sendRedirect(request.getContextPath() + "/index.jsp");
            }else {
                  connection.setAutoCommit(false);
                  ArrayList<DepartmentUser> arrayList = new ArrayList<>();
                  sql = "select department_id,department_name,manager_id,city from departments e left join locations l on e.location_id = l.location_id";
                  preparedStatement = connection.prepareStatement(sql);
                  resultSet = preparedStatement.executeQuery();
                  while (resultSet.next()){
                     String department_id = resultSet.getString("department_id");
                     String department_name = resultSet.getString("department_name");
                     String manager_id = resultSet.getString("manager_id");
                     String city = resultSet.getString("city");
                     DepartmentUser departmentUser = new DepartmentUser(department_id,department_name,manager_id,city);
                     arrayList.add(departmentUser);
                  }
                  request.setAttribute("list",arrayList);
                  connection.setAutoCommit(true);
                  System.out.println("没毛病");
                  request.getRequestDispatcher("/deptList.jsp").forward(request,response);
            }
         } else if ("/dept/Delete".equals(request.getServletPath())) {
            HttpSession session = request.getSession(false);
            if(session == null || session.getAttribute("username") == null){
                  response.sendRedirect(request.getContextPath() + "/index.jsp");
            }else {
                  connection.setAutoCommit(false);
                  String department_id = request.getParameter("department_id");
                  sql = "delete from departments where department_id = ?";
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setInt(1, Integer.parseInt(department_id));
                  int i = preparedStatement.executeUpdate();

                  sql = "delete from employees where department_id = ?";
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setInt(1, Integer.parseInt(department_id));
                  int j = preparedStatement.executeUpdate();
                  connection.setAutoCommit(true);
                  if(i !=0 || j != 0){
                     System.out.println("操作成功");
                  }
                  response.sendRedirect(request.getContextPath() + "/dept/List");
            }

         } else if ("/dept/Detail".equals(request.getServletPath())) {
            HttpSession session = request.getSession(false);
            if(session == null || session.getAttribute("username") == null){
                  response.sendRedirect(request.getContextPath() + "/dept/index.jsp");
            }else {
                  connection.setAutoCommit(false);
                  ArrayList arrayList = new ArrayList();
                  String department_id = request.getParameter("department_id");
                  sql = "select employee_id,last_name,job_id,manager_id,department_id,hiredate from employees where department_id = ?";
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setInt(1, Integer.parseInt(department_id));
                  resultSet = preparedStatement.executeQuery();
                  while (resultSet.next()){
                     String employee_id= resultSet.getString("employee_id");
                     String last_name = resultSet.getString("last_name");
                     String job_id = resultSet.getString("job_id");
                     String manager_id = resultSet.getString("manager_id");
                     department_id = resultSet.getString("department_id");
                     String hiredate = resultSet.getString("hiredate");
                     EmoloyeeUser emoloyeeUser = new EmoloyeeUser(employee_id,last_name,job_id,manager_id,department_id,hiredate);
                     arrayList.add(emoloyeeUser);
                     }
                     connection.setAutoCommit(true);
                     request.setAttribute("detail",arrayList);
                     request.getRequestDispatcher("/deptDetail.jsp").forward(request,response);
            }

         } else if ("/dept/Update".equals(request.getServletPath())) {
            HttpSession session = request.getSession(false);
            if(session == null || session.getAttribute("username") == null){
                  response.sendRedirect(request.getContextPath() + "/dept/index.jsp");
            }else {
                  connection.setAutoCommit(false);
                  String department_id = request.getParameter("department_id");
                  System.out.println(department_id);
                  String department_name = request.getParameter("department_name");
                  String manager_id = request.getParameter("manager_id");
                  String city = request.getParameter("city");

                  sql = "update departments set department_name = ?,manager_id = ? where department_id = ?";
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setString(1,department_name);
                  preparedStatement.setInt(2, Integer.parseInt(manager_id));
                  preparedStatement.setInt(3, Integer.parseInt(department_id));
                  int j = preparedStatement.executeUpdate();

                  sql = "update locations set city = ? where location_id = (select location_id from departments where department_id = ?)";
                  preparedStatement = connection.prepareStatement(sql);
                  preparedStatement.setString(1,city);
                  preparedStatement.setInt(2, Integer.parseInt(department_id));
                  int i = preparedStatement.executeUpdate();
                  if(i != 0 && j != 0){
                     System.out.println("修改成功");
                  }
                  connection.setAutoCommit(true);

                  response.sendRedirect(request.getContextPath() + "/dept/List");
            }

         } else if ("/dept/login".equals(request.getServletPath())) {
            HttpSession session = request.getSession();
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            String flag = request.getParameter("flag");
            System.out.println(flag + "lll");
            if("1".equals(flag)){
                  Cookie cookie1 = new Cookie("username",username);
                  cookie1.setMaxAge(180);
                  cookie1.setPath(request.getContextPath());
                  response.addCookie(cookie1);
                  Cookie cookie2 = new Cookie("password",password);
                  cookie2.setMaxAge(180);
                  cookie2.setPath(request.getContextPath());
                  response.addCookie(cookie2);

            }
            sql = "select * from t_login where username = ? and password = ?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,username);
            preparedStatement.setInt(2, Integer.parseInt(password));
            resultSet = preparedStatement.executeQuery();
            if(resultSet.next()){
                  System.out.println("登录成功");
                  connection.setAutoCommit(true);
                  session.setAttribute("username",username);
                  //aaaaaaaaaaaaaa
                  System.out.println("-----------------------------------");
                  response.sendRedirect(request.getContextPath() + "/dept/List");
            }else {
                  System.out.println("登录失败");
            }
         }
      } catch (ClassNotFoundException e) {
         throw new RuntimeException(e);
      } catch (SQLException e) {
         try {
            connection.rollback();
         } catch (SQLException ex) {
            throw new RuntimeException(ex);
         }
         throw new RuntimeException(e);
      }finally {
         if(resultSet != null){
            try {
                  resultSet.close();
            } catch (SQLException e) {
                  throw new RuntimeException(e);
            }
         }
         if(preparedStatement != null){
            try {
                  preparedStatement.close();
            } catch (SQLException e) {
                  throw new RuntimeException(e);
            }
         }
         if(connection != null){
            try {
                  connection.close();
            } catch (SQLException e) {
                  throw new RuntimeException(e);
            }
         }
      }
}

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

她与晚风 · 发表于 2023-4-30 12:09:25

我的这个页面登录二次跳转有问题

发表于 2023-4-30 12:10:26

您的代码已经实现了免登录功能，这里是通过使用Session和Cookie来实现的。当用户登录后，服务器会将用户名和密码存储在Cookie中，然后在需要进行身份验证的页面，通过读取Cookie中的信息来实现自动登录。

代码的逻辑如下：

1. 获取请求中的所有Cookie。
2. 遍历这些Cookie，找到名为"username"和"password"的Cookie。
3. 如果找到了这两个Cookie，从这些Cookie中获取用户名和密码。
4. 使用获取到的用户名和密码查询数据库以验证用户身份。
5. 如果用户身份验证成功，将用户名存储在Session中，并将用户重定向到部门列表页面。
6. 如果身份验证失败，将用户重定向到登录页面。

为了让您的代码更清晰，我对您的代码进行了一些重构和注释：

package bj;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.*;

import java.io.IOException;
import java.sql.*;

@WebServlet({"/welcome"})
public class welcomePage extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies = request.getCookies();
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        HttpSession session = request.getSession();
        String sql;
        String username = null;
        String password = null;

        // 从Cookie中获取用户名和密码
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                if ("username".equals(cookie.getName())) {
                    username = cookie.getValue();
                }
                if ("password".equals(cookie.getName())) {
                    password = cookie.getValue();
                }
            }
        }

        // 如果找到了用户名和密码，验证用户身份
        if (username != null && password != null) {
            sql = "select * from t_login where username = ? and password = ?";
            System.out.println(username + ":    " + password);
            try {
                Class.forName("com.mysql.cj.jdbc.Driver");
                connection = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/myemployees", "root", "123456");
                preparedStatement = connection.prepareStatement(sql);
                preparedStatement.setString(1, username);
                preparedStatement.setInt(2, Integer.parseInt(password));
                resultSet = preparedStatement.executeQuery();

                // 如果身份验证成功，将用户名存储在Session中，并重定向到部门列表页面
                if (resultSet.next()) {
                    System.out.println("登录成功");
                    connection.setAutoCommit(true);
                    session.setAttribute("username", username);
                    response.sendRedirect(request.getContextPath() + "/dept/List");
                } else {
                    // 身份验证失败，重定向到登录页面
                    System.out.println("登录失败");
                    response.sendRedirect(request.getContextPath() + "/index.jsp");
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            } catch (ClassNotFoundException e) {
                throw new RuntimeException(e);
            }
        } else {
            // 没有找到用户名和密码，重定向到登录页面
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        }
    }
}

这样，您的代码会更易于阅读和理解。

歌者文明清理员 · 发表于 2023-4-30 12:16:02

匿名者发表于 2023-4-30 12:10
您的代码已经实现了免登录功能，这里是通过使用Session和Cookie来实现的。当用户登录后，服务器会将用户名 ...

iskdz

她与晚风 · 发表于 2023-4-30 12:16:44

匿名者发表于 2023-4-30 12:10
您的代码已经实现了免登录功能，这里是通过使用Session和Cookie来实现的。当用户登录后，服务器会将用户名 ...

厉害了哥,可以了,就是欢迎页面有问题
请问一下我写的那个有什么问题呢

她与晚风 · 发表于 2023-4-30 12:30:35

匿名者发表于 2023-4-30 12:10
您的代码已经实现了免登录功能，这里是通过使用Session和Cookie来实现的。当用户登录后，服务器会将用户名 ...

哦哦
username = cookie.getValue();
我这一步写错了

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