初识MyBatis

第一步

创建一个maven项目，在pom.xml中加入

<dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.29</version>
        </dependency>

第二步 创建数据库添加表，同时创建相应的实体（字段名和属性名一致）

添加表数据

创建实体类

package com.itheima.entity;

import java.sql.PreparedStatement;

/**
 * @Author: GenGen
 * @Description: 6Ge
 * @DateTime: 2023/2/23 9:25
 **/
public class Db1User {
    private int ID;
    private String userName;
    private String passWrod;

    public Db1User(int ID, String userName, String passWrod) {
        this.ID = ID;
        this.userName = userName;
        this.passWrod = passWrod;
    }

    public Db1User() {
    }

    public int getID() {
        return ID;
    }

    public void setID(int ID) {
        this.ID = ID;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassWrod() {
        return passWrod;
    }

    public void setPassWrod(String passWrod) {
        this.passWrod = passWrod;
    }

    @Override
    public String toString() {
        return "Db1User{" +
                "ID=" + ID +
                ", userName='" + userName + '\'' +
                ", passWrod='" + passWrod + '\'' +
                '}';
    }
}

第三步 创建MyBatis的核心文件，文件名一般都是mybatis-comfig.xml

<?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>
    <!--通过properties标签加载外部properties文件-->
<!--    <properties resource="jdbc.properties"></properties>-->
    <!-- 环境配置 -->
    <!-- 加载类路径下的属性文件 -->
    <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/db1"/>
                <!--mysql8的url-->
<!--                <property name="url" value="jdbc:mysql://localhost:3306/db1?serverTimezone=UTC&amp;characterEncoding=utf8&amp;useUnicode=true&amp;useSSL=false"/>-->
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <!-- mapper文件路径配置 -->
    <mappers>
        <mapper 
resource="Mapper/UserMapper.xml"/>
    </mappers>
</configuration>

第四步配置UserMapper.xml

<?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="UserMapper">
    <select id="findAll" resultType="com.itheima.entity.Db1User">
        select * from db1User
    </select>
</mapper>

第五步使用mybatis

package com.itheima;

import com.itheima.entity.Db1User;
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 org.junit.Test;
import java.io.IOException;
import java.io.Reader;
import java.util.List;

/**
 * @Author: GenGen
 * @Description: 6Ge
 * @DateTime: 2023/2/23 9:35
 **/
public class userTest {
    @Test
    public void userTest(){
        //读取文件名
        String rr = "mybatis-config.xml";
        //创建IO流
        Reader reader = null;
        try {
            //读取mybatis-config.xml文件内容到reader对象中
            reader = Resources.getResourceAsReader(rr);

        }catch (IOException e){
            e.printStackTrace();
        }
        //初始化mybatis数据库，创建SqlSessionFactory类的实例
        SqlSessionFactory sqlMapper = new SqlSessionFactoryBuilder().build(reader);
        //创建SqlSession实例
        SqlSession sqlSession = sqlMapper.openSession();
        //传入参数查询，返回杰哥哥
        List<Db1User> users = sqlSession.selectList("findAll");
        //输出结果
        System.out.print(users.toString());
        //关闭session
        sqlSession.close();
    }
}