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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>