实现步骤

1.创建一个student表

image.png

2.新建一个maven项目
3.创建一个实体类student，定义属性，属性名，和列名一致

package com.zwx.entity;

public class Student {
    private Integer id;
    private String name;
    private String email;
    private Integer age;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                ", age=" + age +
                '}';
    }
}

4.创建dao接口，定义操作数据库的方法

package com.zwx.dao;

import com.zwx.entity.Student;

public interface StudentDao {
    //查询一个学生
    Student selectStudentById(Integer id);
}

5.创建一个xml文件（mapper文件）写sql语句
mybatis把代码和sql语句分开
mapper文件：定义和dao接口在一个目录，一个表一个mapper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.zwx.dao.StudentDao">

    <select id="selectStudentById" resultType="com.zwx.entity.Student">
        SELECT id,name,email,age FROM mybatis.student WHERE id = #{id}
    </select>
</mapper>

6.创建mybatis的主配置文件(xml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>
<!--    日志-->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <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/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;autoReconnect=true&amp;failOverReadOnly=false"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/zwx/dao/StudentDao.xml"/>
    </mappers>
</configuration>

定义创建链接实例的数据源对象（datasource）
指定其他mapper文件的位置
7.测试

import com.zwx.entity.Student;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;


import org.apache.ibatis.io.Resources;

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

public class Mytest {

    @Test
    public void test() throws IOException {
//        mybatis核心类：SqlSessionFactory
        //定义mybatis主配置文件的位置，从类路径开始的相对路径
        String config="mybatis.xml";
//        读取主配置文件使用mybatis框架中的Resource类
       InputStream inputStream = Resources.getResourceAsStream(config);
       //创建SqlSessionFactory对象，使用SqlSessionFactoryBuilder()
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //获取sqlsession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
//        指定要执行的sql的id
        String sqlId="com.zwx.dao.StudentDao"+"."+"selectStudentById";
//        通过sqlSession的方法 执行sql语句
        Student student = sqlSession.selectOne(sqlId,1101);
        System.out.println(student);
//        关闭sqlsession对象
        sqlSession.close();
    }
}