Request&Response（请求?响应）- 案例

最后更新时间：2022年07月13日

Request&Response（请求?响应）- 案例

用户登录

SQL代码

-- 创建用户表
CREATE TABLE tb_user(
    id int primary key auto_increment,
    username varchar(20) unique,
    password varchar(32)
);

-- 添加数据
INSERT INTO tb_user(username,password) values('zhangsan','123'),('lisi','234');

SELECT * FROM tb_user;

User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 + '\'' +
                '}';
    }
}

坐标配置

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

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.34</version>
        </dependency>

mybatis-config.xml核心配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://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;useServerPrepStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--扫描mapper-->
        <package name="com.itheima.mapper"/>
    </mappers>
</configuration>

UserMapper映射文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.UserMapper">

</mapper>

UserMapper接口

    package com.itheima.mapper;
    
    import com.itheima.pojo.User;
    import org.apache.ibatis.annotations.Insert;
    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用户对象
​         * @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);
​    

        /**
         * 根据用户名查询用户对象
         * @param username
         * @return
         */
        @Select("select * from tb_user where username = #{username}")
        User selectByUsername(String username);
    
        /**
         * 添加用户
         * @param user
         */
        @Insert("insert into tb_user values(null,#{username},#{password})")
        void add(User user);
    }

LoginServlet

    package com.itheima.web;
    
    import com.itheima.mapper.UserMapper;
    import com.itheima.pojo.User;
    import com.itheima.util.SqlSessionFactoryUtils;
    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.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.PrintWriter;
    
    @WebServlet("/loginServlet")
    public class LoginServlet extends HttpServlet {
        @Override
        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);*/
    
            SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();
            //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user释放为null
​            if(user != null){
​                // 登陆成功
​                writer.write("登陆成功");
​            }else {
​                // 登陆失败
​                writer.write("登陆失败");
​            }
​        }
​    

        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            this.doGet(request, response);
        }
    }

login.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>login</title>
    <link href="css/login.css" rel="stylesheet">
</head>

<body>
<div id="loginDiv">
    <form action="/request-demo/loginServlet" method="post" id="form">
        <h1 id="loginMsg">LOGIN IN</h1>
        <p>Username:<input id="username" name="username" type="text"></p>

        <p>Password:<input id="password" name="password" type="password"></p>

        <div id="subDiv">
            <input type="submit" class="button" value="login up">
            <input type="reset" class="button" value="reset">&nbsp;&nbsp;&nbsp;
            <a href="register.html">没有账号？点击注册</a>
        </div>
    </form>
</div>

</body>
</html>

用户注册

register.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>欢迎注册</title>
    <link href="css/register.css" rel="stylesheet">
</head>
<body>

<div class="form-div">
    <div class="reg-content">
        <h1>欢迎注册</h1>
        <span>已有帐号？</span> <a href="login.html">登录</a>
    </div>
    <form id="reg-form" action="/request-demo/registerServlet" method="post">

        <table>

            <tr>
                <td>用户名</td>
                <td class="inputs">
                    <input name="username" type="text" id="username">
                    <br>
                    <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎</span>
                </td>

            </tr>

            <tr>
                <td>密码</td>
                <td class="inputs">
                    <input name="password" type="password" id="password">
                    <br>
                    <span id="password_err" class="err_msg" style="display: none">密码格式有误</span>
                </td>
            </tr>

        </table>

        <div class="buttons">
            <input value="注 册" type="submit" id="reg_btn">
        </div>
        <br class="clear">
    </form>

</div>
</body>
</html>

registerServlet

package com.itheima.web;

import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import com.itheima.util.SqlSessionFactoryUtils;
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.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.InputStream;

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 接收用户数据
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //封装用户对象
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        //2. 调用mapper 根据用户名查询用户对象
        //2.1 获取SqlSessionFactory对象
       /* String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);*/
        SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();

        //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 u = userMapper.selectByUsername(username);

        //3. 判断用户对象释放为null
        if( u == null){
            // 用户名不存在，添加用户
            userMapper.add(user);

            // 提交事务
            sqlSession.commit();
            // 释放资源
            sqlSession.close();
        }else {
            // 用户名存在，给出提示信息
            response.setContentType("text/html;charset=utf-8");
            response.getWriter().write("用户名已存在");
        }

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }
}

代码优化

问题

  • 代码重复：工具类
  • SqlSessionFactory 工厂只创建一次，不要重复创建︰静态代码块

实例

package com.itheima.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        //静态代码块会随着类的加载而自动执行，且只执行一次

        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }
}

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