简易的Web登录功能（Servlet，mybatis，MySQL）-编程知识

效果

在这里插入图片描述

介绍

javaEE项目，见123

JDK8，JavaEE8

项目结构(下面没写的文件就是空的，或者系统自动生成的)
在这里插入图片描述
mysql中的表

步骤

创建Web页面
引入mybatis,MySQL依赖
写后端程序()

1 创建Web页面

index.html

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><link href="style.css" rel="stylesheet"><script src="test.js"></script>
</head><body>
<h1>登录</h1>
<form method="post" action="login"><!--    method="post"表示表单数据将以POST方式提交到服务器。--><!--    action="login"指定表单数据提交的目标地址为"login"。前面不要加"/"--><label for="input-username">账号:</label><input type="text" id="input-username" placeholder="账号" name="username"/><br><label for="input-password">密码:</label><input type="password" id="input-password" placeholder="密码" name="password"/><br><div><button onclick="http()">登录</button></div>
</form>
</body>
</html>

style.css

body {background-color: #ffffff;margin: 0;text-align: center;
}input {border: 0;background: #e0e0e0;line-height: 40px;border-radius: 20px;padding: 0 20px 0 20px;width: 200px;font-size: 16px;margin-top: 20px;
}input:focus {outline: 0;
}button {margin-top: 20px;background: #6600CC;border-radius: 30px;border: 0;width: 200px;height: 50px;color: white;font-size: 16px;box-shadow: 0px 2px 10px blueviolet;/*按键四周的阴影*/
}button:focus {outline: 0;background: #6666CC;
}#input-remember {width: auto;
}

2 引入mybatis,MySQL依赖

引入maven依赖

<!--        lombok插件-->
<dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.32</version>
</dependency>
<!--        mybatis-->
<dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.7</version>
</dependency>
<!--        MySQL-->
<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.33</version>
</dependency>

3 写后端程序

3.1 mybatis相关

mybatis-config.xml

mybatis-config.xml（从官网复制，再自己加配置）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><environments default="development"><environment id="development"><transactionManager type="JDBC"/><dataSource type="POOLED"><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/study"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><!--    mapper文件，在这注册--><mappers><mapper class="com.example.mapper.UserMapper"/></mappers>
</configuration>

User.java

package com.example.entity;
import lombok.Data;
@Data
public class User {int id;String username;String password;
}

UserMapper.Java

package com.example.mapper;import com.example.entity.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;public interface UserMapper {//用注解，不用xml@Select("select * from users where username = #{username} and password = #{password}")User getUser(@Param("username") String username, @Param("password") String password);
}

3.2 Servlet相关

LoginServlet

package com.example.servlet;import com.example.entity.User;
import com.example.mapper.UserMapper;
import lombok.SneakyThrows;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;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.util.Arrays;
import java.util.Map;@WebServlet(value = "/login", loadOnStartup = 1)
public class LoginServlet extends HttpServlet {SqlSessionFactory factory;@SneakyThrows@Overridepublic void init() throws ServletException {factory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {{//查看前端发来的账号和密码，debug// 遍历并打印请求参数映射表req.getParameterMap().forEach((k, v) -> {// 输出参数键值对，其中值以数组形式显示System.out.println(k + ": " + Arrays.toString(v));});}{// 设置响应内容类型为HTML，编码方式为UTF-8resp.setContentType("text/html;charset=UTF-8");// 获取请求中的表单参数Map<String, String[]> map = req.getParameterMap();// 检查表单中是否包含了用户名和密码字段if (map.containsKey("username") && map.containsKey("password")) {// 获取用户名和密码String username = req.getParameter("username");String password = req.getParameter("password");// 使用try-with-resources确保SqlSession正确关闭try (SqlSession sqlSession = factory.openSession(true)) {// 获取UserMapper接口的实现UserMapper userMapper = sqlSession.getMapper(UserMapper.class);// 尝试根据用户名和密码从数据库中获取用户信息User user = userMapper.getUser(username, password);// 根据用户信息的存在与否返回不同的响应if (user != null) {resp.getWriter().write("用户" + username + "登录成功");} else {resp.getWriter().write("账号/密码错误 或 用户不存在");}}// TODO: 进行权限校验} else {// 如果表单信息不完整，则返回错误信息resp.getWriter().write("错误，表单信息不完整！");}}}
}