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手把手逐步解析Javaweb登录实例

本文主要是介绍手把手逐步解析Javaweb登录实例，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

一、编写前端界面

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        html {
            height: 100%;
        }
        body {
            height: 100%;
        }
        .container {
            height: 100%;
            background-image: linear-gradient(to right, #fbc2eb, #a6c1ee);
        }
        .login-wrapper {
            background-color: #fff;
            width: 358px;
            height: 588px;
            border-radius: 15px;
            padding: 0 50px;
            position: relative;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }
        .header {
            font-size: 38px;
            font-weight: bold;
            text-align: center;
            line-height: 200px;
        }
        .input-item {
            display: block;
            width: 100%;
            margin-bottom: 20px;
            border: 0;
            padding: 10px;
            border-bottom: 1px solid rgb(128, 125, 125);
            font-size: 15px;
            outline: none;
        }
        .input-item:placeholder {
            text-transform: uppercase;
        }
        .btn {
            text-align: center;
            padding: 10px;
            width: 100%;
            margin-top: 40px;
            background-image: linear-gradient(to right, #a6c1ee, #fbc2eb);
            color: #fff;
            border-style:none;
        }
        .msg {
            text-align: center;
            line-height: 88px;
        }
        a {
            text-decoration-line: none;
            color: #abc1ee;
        }
    </style>
</head>
<body>
<div class="container">
    <div class="login-wrapper">
        <div class="header">Login</div>
        <div class="form-wrapper">
            <form action="" id="form">
                <input type="text" name="username" placeholder="username" class="input-item">
                <input type="password" name="password" placeholder="password" class="input-item">
                <input type="submit" class="btn" value="Ligin">
            </form>
        </div>
        <div class="msg">
            Don't have account?
            <a href="index1.html">Sign up</a>
        </div>
    </div>
</div>
</body>
</html>

二、创建数据库数据表

CREATE TABLE tb_user(
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(20) UNIQUE,
	PASSWORD VARCHAR(32)
	);
	
	INSERT INTO tb_user(username,PASSWORD) VALUES('zhangsan','123'),('lisi','234');
	
	SELECT * FROM tb_user;

三、创建项目，编写实体类

package com.itheima.pojo;

public class User {
    private Integer id;
    private String username;
    private String password;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

四、导入mybatis，mysql驱动坐标

 <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
        </dependency>

五、创建mybatis-config.xml核心配置文件，UserMapper.xml映射文件，UserMapper接口

resource目录下的核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 起别名 -->
    <typeAliases>
        <package name="com.itheima.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///db1?useSSL=false&amp;useServerPreStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 包扫描，扫描mapper -->
        <package name="com.itheima.mapper"/>
    </mappers>
</configuration>

创建itheima目录下的mapper包的UserMapper接口

创建resource目录下的itheima目录下的mapper包的UserMapper.xml映射文件

六、补全代码

  1. UserMapper接口（此处用了注解的方式，所以没写映射文件）
package com.itheima.mapper;

import com.itheima.pojo.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

public interface UserMapper {

    /**
     * 根据用户名和密码查询对象
     * @param username
     * @param password
     * @return
     */
    @Select("select * from tb_user where username = #{username} and password = #{password}")
    User Select(@Param("username") String username, @Param("password") String password);
}
  1. html代码（补全表单跳转的servlet）
<form action="/tomcat-demo2/loginServlet" method="post" id="form">
  1. 编写servlet
package com.itheima.web;

import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
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.io.InputStream;
import java.io.PrintWriter;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1. 接收用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        // 2. 调用mybatis完成查询
        // 2.1 获取sqlSessionFactory对象
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 2.2 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 2.3 获取Mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        // 2.4 调用方法
        User user = userMapper.Select(username, password);
        // 2.5 释放资源
        sqlSession.close();

        //获取字符输出流，并设置content type
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        // 3. 判断uer是否为null
        if (user != null){
            //登录成功
            writer.write("登录成功");
        }else {
            //登录失败
            writer.write("登录失败");
        }
    }
}

此时代码就可以正常运行了，需要注意的是，pom文件中一定要注意mysql的驱动是自己下载的驱动，如果是maven导入的驱动会报错。我在此处犯了两次错误，浪费了许多时间！

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