目录
package cn.hp.util;import java.sql.*;public class JDBCUtils { static Connection connection = null ; static Statement statement = null ; static PreparedStatement preparedStatement = null ; static ResultSet resultSet = null ; static{ try { Class.forName("com.mysql.jdbc.Driver"); connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/user_system?characterEncoding=utf8&serverTimezone=UTC", "root", "root"); } catch (ClassNotFoundException | SQLException e) { e.printStackTrace(); } }// 新增和修改 DML 操作 String sql ， sql中的参数 preparedStatement Object[] arr 用来补全sql中的? public static int DML(String sql , Object[] arr ){ // 可变参数 Object ... arr 0~n个参数 int update = 0 ; try{ preparedStatement = connection.prepareStatement(sql);// 循环完毕，会将sql中全部? 补充齐 for (int i = 0 ; i < arr.length ; i++){ preparedStatement.setObject(i+1 , arr[i] ); } update = preparedStatement.executeUpdate(); }catch (SQLException e){ e.printStackTrace(); } return update ; } // 带参查询 DQL 操作 public static ResultSet DQL(String sql , Object[] arr ){ try{ preparedStatement = connection.prepareStatement(sql);// 循环完毕，会将sql中全部? 补充齐 for (int i = 0 ; i < arr.length ; i++){ preparedStatement.setObject(i+1 , arr[i] ); } resultSet = preparedStatement.executeQuery(); }catch (SQLException e){ e.printStackTrace(); } return resultSet ; } // 单独提供关闭资源方法 public static void close(){ try { if (statement!=null){ statement.close(); } if (connection!= null){ connection.close(); } } catch (SQLException e) { e.printStackTrace(); } }}
package cn.hp.service;import cn.hp.dao.UserDao;public class UserService { public boolean login(String account, String password) { //service层，依赖于dao层 制定某一条sql执行 UserDao userDao = new UserDao(); int select = userDao.selectByAccountAndPassword(account ,password); if (select>0){ return true; }else { return false; } } public boolean check(String account) { //service层，依赖于dao层 制定某一条sql执行 UserDao userDao = new UserDao(); int select = userDao.selectByAccount(account); if (select>0){ return true; }else { return false; } }}
package cn.hp.servlet;import cn.hp.service.UserService;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;@WebServlet("/login")public class LoginServlet extends HttpServlet { @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.设置用户输入的编码格式，因为有可能是中文 req.setCharacterEncoding("utf-8"); //2.获取用户数输入的内容 String account = req.getParameter("account"); String password = req.getParameter("password"); //3.依据service来判断当前登录的账号密码是否正确 //User表 定义一个UserService 用来处理 所有和user有关的业务 UserService userService = new UserService(); //login方法传入账号密码 返回是否登录成功 boolean flag = userService.login(account,password); //4.依据是否登录成功，进行控制页面的跳转 if (flag){ req.getRequestDispatcher("success.jsp").forward(req,resp); }else { req.setAttribute("msg","密码错误，请重新登录！"); req.getRequestDispatcher("login.jsp").forward(req,resp); } }}
package cn.hp.servlet;import cn.hp.service.UserService;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;@WebServlet("/check")public class CheckServlet extends HttpServlet { @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.设置用户输入的编码格式，因为有可能是中文 req.setCharacterEncoding("utf-8"); //2.获取用户数输入的内容 String account = req.getParameter("account"); //3.依据service来判断当前登录的账号密码是否正确 //User表 定义一个UserService 用来处理 所有和user有关的业务 UserService userService = new UserService(); //使用check方法 检出是否存在用户 true 存在用户 false 不存在 boolean flag = userService.check(account); resp.getWriter().println(flag); }}
package cn.hp.dao;import cn.hp.util.JDBCUtils;import java.sql.ResultSet;import java.sql.SQLException;public class UserDao { public int selectByAccountAndPassword(String account, String password) { //执行select查询sql语句 String sql = "select count(*) from user where account = ? and password = ?"; Object[] objects = {account , password}; ResultSet resultSet = JDBCUtils.DQL(sql,objects); int select = 0; try { while (resultSet.next()){ select = resultSet.getInt(1); } }catch (SQLException e){ e.printStackTrace(); } return select; } public int selectByAccount(String account) { //执行select查询sql语句 String sql = "select count(*) from user where account = ? "; Object[] objects = {account }; ResultSet resultSet = JDBCUtils.DQL(sql,objects); int select = 0; try { while (resultSet.next()){ select = resultSet.getInt(1); } }catch (SQLException e){ e.printStackTrace(); } return select; }}
<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>登录页</title> <script src="js/jquery-3.6.0.js"></script></head><body> <form action="login"> 账号：<input id="input1" type="text" name="account" /> <span id="span1"></span> <br/> 密码：<input type="password" name="password" /> <span style="color:red"> ${msg } </span><br/> <input type="submit" value="登录"/> </form></body><script> // 使用jQuery完成ajax校验 ，当前账号是否存在 $("#input1").blur(function () { // 发送ajax请求，获取到当前输入的账号是否存在，写入到span1标签中 let account = $("#input1").val(); $.ajax({ url:"check", // data:{"account":$("#input1").val() }, data:"account="+account , type:"get", success:function (data) { let data1 = JSON.parse(data); if (data1){ // 表示存在当前账号 // 可以登录 $("#span1").html("可以登录"); $("#span1").attr("style","color:green"); }else { $("#span1").html("未注册"); $("#span1").attr("style","color:red"); } } }) })</script></html>
当你感到悲哀痛苦时，最好是去学些什么东西。
