1. 导入依赖

<dependencies>
    <!-- mybatis-plus插件依赖 -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus</artifactId>
        <version>3.1.1</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.17</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.1.20</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.10</version>
        <scope>provided</scope>
    </dependency>

    <!-- https://mvnrepository.com/artifact/junit/junit -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.30</version>
        <scope>test</scope>
    </dependency>
</dependencies>

2.配置log4j日志文件

log4j.properties

log4j.rootLogger=DEBUG,A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender 
log4j.appender.A1.layout=org.apache.log4j.PatternLayout 
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

3.配置Mybatis配置文件

mybatis-conﬁg.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>
    <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://127.0.0.1:3306/mp?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=Hongkong"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

4.编写Mapper接口

import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;

import java.util.List;

public interface UserMapper extends BaseMapper<User> {
    List<User> findAll();
}

5.编写*Mapper.xml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="cn.itcast.mp.simple.mapper.UserMapper">
    <select id="findAll" resultType="cn.itcast.mp.simple.pojo.User">
        select * from tb_user;
    </select>
</mapper>

6.编写测试类

package cn.itcast.mp.simple;

import cn.itcast.mp.simple.mapper.UserMapper;
import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
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.InputStream;
import java.util.List;


public class MpTest {
    @Test
    public void test01() throws Exception {
        String config = "mybatis-conﬁg.xml";
        InputStream inputStream = Resources.getResourceAsStream(config);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession sqlSession = sqlSessionFactory.openSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> lists = userMapper.findAll();
        //List<User> lists = userMapper.selectList(null);

        for (User list : lists) {
            System.out.println(list);
        }
    }
}

测试结果

到这里前期工作做完了

开始正式进入Mybatis-puls程序

7.MybatisSqlSessionFactoryBuilder

Mybatis中使用SqlSessionFactoryBuilder创建SqlSession而Mybatis-plus中使用MybatisSqlSessionFactoryBuilder进程构建SqlSession

测试代码改为

package cn.itcast.mp.simple;

import cn.itcast.mp.simple.mapper.UserMapper;
import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
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.InputStream;
import java.util.List;


public class MpTest {
    @Test
    public void test01() throws Exception {
        String config="mybatis-conﬁg.xml";
        InputStream inputStream = Resources.getResourceAsStream(config);
      //  MybatisSqlSessionFactoryBuilder
        SqlSessionFactory sqlSessionFactory=new MybatisSqlSessionFactoryBuilder().build(inputStream);

        SqlSession sqlSession=sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> lists = userMapper.selectList(null);

        for (User list : lists) {
            System.out.println(list);
        }
    }
}

8.运行测试

会发现报错

会发现保错，Table ‘mp.user’ doesn’t exist，因为这里还要有一个注解@TableName

在实体类中加上此注解即可，

实体类代码修改为：

@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;

}