目录结构

UserDao.java

package com.xxgc.mybatis.dao;

import com.xxgc.mybatis.po.User;

import java.util.List;

//用户表Dao层接口
public interface UserDao {
    //查询所有用户
    List<User> selectAllUsers();
}

UserDaoMapper.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">
<!--映射一个/绑定一个 dao层接口-->
<mapper namespace="com.xxgc.mybatis.dao.UserDao">
    <!--id 对应接口里的方法名 -->
    <!--resultType 返回结果类型-->
    <select id="selectAllUsers" resultType="com.xxgc.mybatis.po.User">
        select * from users;
    </select>


    
</mapper>

User.java

package com.xxgc.mybatis.po;

/* alt + insert 生成构造函数 */
public class User {
    private long uId;
    private String uName;
    private String uPass;

    @Override
    public String toString() {
        return "User{" +
                "uId=" + uId +
                ", uName='" + uName + '\'' +
                ", uPass='" + uPass + '\'' +
                '}';
    }

    public long getuId() {
        return uId;
    }

    public void setuId(long uId) {
        this.uId = uId;
    }

    public String getuName() {
        return uName;
    }

    public void setuName(String uName) {
        this.uName = uName;
    }

    public String getuPass() {
        return uPass;
    }

    public void setuPass(String uPass) {
        this.uPass = uPass;
    }
}

MyBatisUtils.java

package com.xxgc.mybatis.util;

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

//Mybaits工具类，用来获取sqlSession
public class MyBatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //以下三步通过配置文件来获取sqlSessionFactory
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            /* ctrl + alt + f 提取/抽取 全局变量 */
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e){
            e.printStackTrace();
        }
    }

    

    public static SqlSession getSqlSession(){
        /* ctrl + alt + v 自动生成返回结果 */
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

mybatis-config.xml

<?xml version="1.0" encoding="utf8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--核心配置文件-->
<configuration>
    <!--开启驼峰命名-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!--environments 环境  -->
    <environments default="development">
        <environment id="development">
            <!--事务 JDBC的事务-->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--serverTimezone=GMT 时区-->
                <!--useSSL=true 通道加密-->
                <!--useUnicode=true 自定义编码-->
                <!--characterEncoding=UTF-8 设置编码为UTF-8-->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=GMT&amp;
                useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--每一个持久层接口都对应一个mapper文件 mapper文件需要手动注入-->
    <mappers>
        <mapper resource="com\xxgc\mybatis\dao\UserDaoMapper.xml"/>
    </mappers>


</configuration>

UserDaoTest.java

package com.xxgc.mybatis.dao;

import com.xxgc.mybatis.po.User;
import com.xxgc.mybatis.util.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    //单元测试
    //不需要启动整个工程，只需要加载测试所依赖的模块
    @Test
    public void test(){
        //调用工具类 得到sqlSession
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        //加载dao层映射
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        //通过调用接口执行语句
        List<User> users = mapper.selectAllUsers();
        //循环打印内容
        for (User user : users) {
            System.out.println("user = " + user);
        }
        //手动关闭sqlsession(学到了spring过后就不需要了)
        sqlSession.close();
    }
}

pom.xml

<?xml version="1.0" encoding="utf8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.xxgc</groupId>
    <artifactId>MyBatisDemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!--导入依赖-->
    <dependencies>
        <!--mybatis的依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>

        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.44</version>
        </dependency>

        <!--junit单元测试包-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <!--配置文件UTF-8错误-->
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <!--配置Maven过滤器，过滤掉xml，让xml也进行编译-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>


</project>

Sql语句

/*
SQLyog Ultimate v12.09 (64 bit)
MySQL - 5.5.54 : Database - mybatis
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`mybatis` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `mybatis`;

/*Table structure for table `users` */

DROP TABLE IF EXISTS `users`;

CREATE TABLE `users` (
  `u_id` BIGINT(18) NOT NULL AUTO_INCREMENT,
  `u_name` VARCHAR(30) NOT NULL COMMENT '用户名',
  `u_pass` VARCHAR(100) NOT NULL COMMENT '密码',
  PRIMARY KEY (`u_id`)
) ENGINE=INNODB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

/*Data for the table `users` */

insert  into `users`(`u_id`,`u_name`,`u_pass`) values (1,'张三','9033241'),(2,'李四','3333241'),(3,'王五','12156241'),(4,'赵六','1111'),(5,'铁蛋','23233241');

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;