图书管理系统（图书录入和管理，借阅管理，图书管理）

package com.example.demo.servlet; import com.example.demo.utils.JDBCUtil; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; /** * @author jiang * @create 2024/5/22 */ //登录接口 @WebServlet(name = "loginServlet", value = "/login-servlet") public class LoginServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // super.doPost(req, resp); try (Connection con = JDBCUtil.getCon();){ String sqlByCou = "select count(1) as num from user where username = ? and password = ?"; String sqlByUser = "select id from user where username = ? and password = ?"; PreparedStatement preparedStatement = con.prepareStatement(sqlByCou); preparedStatement.setString(1,req.getParameter("username")); preparedStatement.setString(2,req.getParameter("password")); ResultSet resultSet = preparedStatement.executeQuery(); // boolean next = resultSet.next(); // int num = resultSet.getInt("num"); while (resultSet.next()){ int num = resultSet.getInt("num"); if (num != 1){ req.setAttribute("prompt","账号密码错误"); req.getRequestDispatcher("/login.jsp").forward(req,resp); }else { // 存储当前登陆人信息 PreparedStatement preparedStatementByUser = con.prepareStatement(sqlByUser); preparedStatementByUser.setString(1,req.getParameter("username")); preparedStatementByUser.setString(2,req.getParameter("password")); ResultSet resultSet1 = preparedStatementByUser.executeQuery(); resultSet1.next(); getServletContext().setAttribute("userId",resultSet1.getInt("id")); System.out.println(getServletContext().getAttribute("userId")); resp.sendRedirect(req.getContextPath()+"/bookList"); // req.getRequestDispatcher("/bookList").forward(req,resp); } } // if (resul) } catch (SQLException e) { throw new RuntimeException(e); } } }