1. 准备工作

数据库准备:

创建Maven 父模块

2. Mybatis 整合 Mybatis-Plus

创建子模块:

准备 log4j.properties 日志文件

3. Mybatis 原生写法实现查询User

编写mybatis-config.xml文件：

编写User实体对象：（这里使用lombok进行了进化bean操作）

编写UserMapper接口

编写UserMapper.xml文件：

编写TestMybatis测试用例：

4. Mybatis + Mybatis-Plus整合查询User

将UserMapper继承BaseMapper，将拥有了BaseMapper中的所有方法：

使用MP中的MybatisSqlSessionFactoryBuilder进行构建：

运行报错:

解决: 在User对象中添加 @TableName, 指定该类映射的数据库表名. (默认是数据库.实体类类名小写)

测试结果:

简要说明:

5. Spring + Mybatis + Mybatis-Plus整合

创建子Module

编写jdbc.properties

编写log4j.properties

编写applicationContext.xml

编写User对象以及UserMapper接口：

编写测试用例：

测试结果：

6.SpringBoot + Mybatis + Mybatis-Plus整合查询User

创建SpringBoot项目导入相关依赖

log4j.properties：

编写application.properties

编写pojo 和 mapper

编写启动类

编写测试用例

测试结果

对于Mybatis整合MybatisPlus常常有三种用法，分别是 Mybatis + Mybatis-Plus 、Spring + Mybatis + Mybatis-Plus、SpringBoot + Mybatis + Mybatis-Plus

1. 准备工作

数据库准备:

-- 创建数据库
create database mybatis_plus_practice;
-- 使用数据库
USE mybatis_plus_practice;

-- 创建测试表
CREATE TABLE `tb_user` (
`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
`user_name` varchar(20) NOT NULL COMMENT '用户名',
`password` varchar(20) NOT NULL COMMENT '密码',
`name` varchar(30) DEFAULT NULL COMMENT '姓名',
`age` int(11) DEFAULT NULL COMMENT '年龄',
`email` varchar(50) DEFAULT NULL COMMENT '邮箱',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
-- 插入测试数据
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) 
VALUES('1', 'zhangsan', '123456', '张三', '18', 'test1@163.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES('2', 'lisi', '123456', '李四', '20', 'test2@163.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES('3', 'wangwu', '123456', '王五', '28', 'test3@163.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES('4', 'zhaoliu', '123456', '赵六', '21', 'test4@163.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES('5', 'sunqi', '123456', '孙七', '24', 'test5@163.cn');

创建Maven 父模块

<?xml version="1.0" encoding="UTF-8"?>
<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>indi.darylz</groupId>
    <artifactId>mybatis-plus-simple</artifactId>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-plus-mybatis</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>
    <packaging>pom</packaging>

    <!-- 导入相关依赖-->
    <dependencies>
        <!-- mybatis-plus插件依赖 -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus</artifactId>
            <version>3.1.1</version>
        </dependency>
        <!-- MySql 连接驱动  -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
        <!-- 连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.11</version>
        </dependency>

        <dependency>
            <!-- 简化bean代码的工具包 -->
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
            <version>1.18.4</version>
        </dependency>
        <!-- 单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!-- 日志工具包-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.6.4</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

2. Mybatis 整合 Mybatis-Plus

创建子模块:

<?xml version="1.0" encoding="UTF-8"?><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>
    <parent>
        <groupId>indi.darylz</groupId>
        <artifactId>mybatis-plus-simple</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <packaging>jar</packaging>
    <artifactId>mybatis-plus-mybatis</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

</project>

准备 log4j.properties 日志文件

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. Mybatis 原生写法实现查询User

编写mybatis-config.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>
    <settings>
        <!-- 开启驼峰，开启后，只要数据库字段和对象属性名字母相同，
        无论中间加多少下划线都可以识别 -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <environments default="development">
        <!-- 配置数据源 -->
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 由于使用的mysql8的版本, 驱动类是 com.mysql.cj.jdbc.Driver
                mysql5驱动版本是 com.mysql.jdbc.Driver-->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <!-- 由于使用的mysql8的版本,  url中一定要加入时区! 否则报时区错误异常
                #北京东八区 serverTimezone=GMT%2B8
                #上海时区 serverTimezone=Asia/Shanghai-->
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis_plus_practice?serverTimezone=GMT%2B8&amp;
                characterEncoding=utf8&amp;useUnicode=true&amp;useSSL=true"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 通过resource属性引入classpath路径的相对资源-->
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

编写User实体对象：（这里使用lombok进行了进化bean操作）

package indi.darylz.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author daryl z
 * @description description_write_here
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

编写UserMapper接口

package indi.darylz.mapper;

import indi.darylz.pojo.User;

import java.util.List;

/**
 * @author: daryl z
 * @description: description_write_here
 */
public interface UserMapper {
    List<User> findAll();
}

编写UserMapper.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="indi.darylz.mapper.UserMapper">
    <select id="findAll" resultType="indi.darylz.pojo.User">
        SELECT * FROM tb_user;
    </select>
</mapper>

编写TestMybatis测试用例：

package indi.darylz;

import indi.darylz.mapper.UserMapper;
import indi.darylz.pojo.User;
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.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @author: daryl z
 * @description: description_write_here
 */
public class TestMybatis {
    private UserMapper userMapper;

    @Before
    public void getUserMapperInstance() throws IOException {
        String resource = "mybatis-config.xml";
        // 读取当前类路径下的配置文件获取一个 输出流
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 然后 再通过 Mybatis 的 会话工厂建造器,获取一个会话工厂
        SqlSessionFactory sessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);
        // 打开会话获取一个 会话实例
        SqlSession sqlSession = sessionFactory.openSession();
        // 通过 会话实例 get 一个 UserMapper 的 代理对象
        userMapper = sqlSession.getMapper(UserMapper.class);

    }

    @Test
    public void testFindAll() {
        List<User> userList = userMapper.findAll();
        for (User user : userList) {
            System.out.println(user);
        }
    }
}

测试结果:

4. Mybatis + Mybatis-Plus整合查询User

将UserMapper继承BaseMapper，将拥有了BaseMapper中的所有方法：

package indi.darylz.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import indi.darylz.pojo.User;

import java.util.List;

/**
 * @author: daryl z
 * @description: description_write_here
 */
public interface UserMapper extends BaseMapper<User> {
    List<User> findAll();
}

使用MP中的MybatisSqlSessionFactoryBuilder进行构建：

package indi.darylz;

import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
import indi.darylz.mapper.UserMapper;
import indi.darylz.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @author: daryl z
 * @description: description_write_here
 */
public class TestMybatisMybatisPlus{
    private UserMapper userMapper;

    @Before
    public void getUserMapperInstance() throws IOException {
        String resource = "mybatis-config.xml";
        // 读取当前类路径下的配置文件获取一个 输出流
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //这里使用的是Mybatis-Plus 中的MybatisSqlSessionFactoryBuilder 进行构建
        SqlSessionFactory sessionFactory =
                new MybatisSqlSessionFactoryBuilder().build(inputStream);
        // 打开会话获取一个 会话实例
        SqlSession sqlSession = sessionFactory.openSession();
        // 通过 会话实例 get 一个 UserMapper 的 代理对象
        userMapper = sqlSession.getMapper(UserMapper.class);

    }

    @Test
    public void testSelectList() {
        List<User> userList = userMapper.selectList(null);
        for (User user : userList) {
            System.out.println(user);
        }
    }
}

运行报错:

解决: 在User对象中添加 @TableName, 指定该类映射的数据库表名. (默认是数据库.实体类类名小写)

package indi.darylz.pojo;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author daryl z
 * @description description_write_here
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

测试结果:

简要说明:

由于使用 MybatisSqlSessionFactoryBuilder(这个类是 Mybatis官方的 SqlSessionFactoryBuilder 类的子类 )进行了构建,继承的BaseMapper中的方法就载入到了SqlSession中, 所以就可以直接使用相关的方法;

5. Spring + Mybatis + Mybatis-Plus整合

引入了Spring框架，数据源、构建等工作就交给了Spring管理。

创建子Module

<?xml version="1.0" encoding="UTF-8"?>
<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">
    <parent>
        <groupId>indi.darylz</groupId>
        <artifactId>mybatis-plus-simple</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-plus-spring</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring.version>5.1.8.RELEASE</spring.version>
    </properties>

    <dependencies>
        <!-- 导入Spring相关依赖-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>
    </dependencies>
</project>

编写jdbc.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mybatis_plus_practice?serverTimezone=GMT%2B8&characterEncoding=utf8&useUnicode=true&useSSL=true
jdbc.username=root
jdbc.password=root

编写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

编写applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
https://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 启动Spring项目时扫描到 数据库连接的配置文件 -->
    <context:property-placeholder location="classpath:*.properties"/>

    <!-- 配置数据源 -->
    <bean class="com.alibaba.druid.pool.DruidDataSource" id="dataSource" destroy-method="close">
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
        <property name="driverClassName" value="${jdbc.driver}"/>
        <!-- maxActive: 最主要参数，配置连接池同时能维持的最大连接数，如果客户端理论上需要100个连接，则这个值设为100。 -->
        <property name="maxActive" value="10"/>
        <!--minIdle：连接池中的最小空闲连接数，Druid会定时扫描连接池的连接，
        如果空闲的连接数大于该值，则关闭多余的连接，
        反之则创建更多的连接以满足最小连接数要求。-->
        <property name="minIdle" value="5"/>
    </bean>

    <!-- 这里使用 Mybatis-Plus提供的 sqlSessionFactory,完成 Spring与Mybatis-Plus的整合 -->
    <bean class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean"
          id="mybatisSqlSessionFactoryBean">
        <!-- 将druid连接池注入到 MybatisSqlSessionFactoryBean 的 dataSource属性 中 -->
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!-- 扫描mapper 接口, 使用的依然是 Mybatis原生的扫描器 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <!-- 将包名注入到 MapperScannerConfigurer 的  basePackage 中 -->
        <property name="basePackage" value="indi.darylz.mapper"/>
    </bean>
</beans>

编写User对象以及UserMapper接口：

package indi.darylz.pojo;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author daryl z
 * @description description_write_here
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

package indi.darylz.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import indi.darylz.pojo.User;

/**
 * @author: daryl z
 * @description: description_write_here
 */
public interface UserMapper extends BaseMapper<User> {
}

编写测试用例：

package indi.darylz.test;

import indi.darylz.mapper.UserMapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

/**
 * @author: daryl z
 * @description: description_write_here
 */
// 注入 Spring整合Junit的 运行器
@RunWith(SpringJUnit4ClassRunner.class)
// 指定上下文配置, 读取哪个文件的配置?
@ContextConfiguration(locations = "classpath:application-context.xml")
public class TestSpringMybatisPlus {
    /* 注入UserMapper的代理对象 */
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void testSelectList(){
        userMapper.selectList(null).forEach(System.out::println);
    }
    
}

测试结果：

6.SpringBoot + Mybatis + Mybatis-Plus整合查询User

使用SpringBoot将进一步的简化 Mybatis-Plus的整个, 需要注意的是,由于使用SpringBoot 需要继承 parent, 所以需要重新创建工程, 而不是去创建一个子Module

创建SpringBoot项目导入相关依赖

<?xml version="1.0" encoding="UTF-8"?>
<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">
    <!-- SpringBoot 父模块 GAV -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
    </parent>

    <modelVersion>4.0.0</modelVersion>
    <groupId>indi.darylz</groupId>
    <artifactId>mybatis-plus-springboot</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- 导入 SpringBoot相关依赖-->
        <!-- SpringBoot启动器 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <!-- 测试启动器 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!--简化代码的工具包-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <!--mybatis-plus启动器的 springboot支持-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.0</version>
        </dependency>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
        <!-- 日志工具包 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
        </dependency>
    </dependencies>
    <!-- 打包插件 -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

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
# 关闭 springboot2 的自动装配日志报告 CONDITIONS EVALUATION REPORT
# 的 debug 级别, 更改为 error级别, 不然有的日志看不见,
# 比如有时 Mybatis-Plus生成SQL语句的日志
log4j.logger.org.springframework.boot.autoconfigure=ERROR

编写application.properties

spring.application.name=darylz-mybatis-plus-springboot

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mybatis_plus_practice?serverTimezone=GMT%2B8&characterEncoding=utf8&useUnicode=true&useSSL=true
spring.datasource.username=root
spring.datasource.password=root

编写pojo 和 mapper

package indi.darylz.pojo;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author daryl z
 * @description description_write_here
 */
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;
}

package indi.darylz.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import indi.darylz.pojo.User;


/**
 * @author: daryl z
 * @description: description_write_here
 */
public interface UserMapper extends BaseMapper<User> {
}

编写启动类

package indi.darylz;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * @author: daryl z
 * @description: description_write_here
 */
@MapperScan("indi.darylz.mapper") // 设置 mapper 接口的扫描基包
@SpringBootApplication
public class SpringBootMybatisPlusApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootMybatisPlusApplication.class, args);
    }
}

编写测试用例

package indi.darylz;

import indi.darylz.mapper.UserMapper;
import indi.darylz.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.List;

/**
 * @author: daryl z
 * @description: description_write_here
 */
@RunWith(SpringRunner.class)
@SpringBootTest
public class TestMybatisPlusSpringBoot {
    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelectList() {
        List<User> users = userMapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }
}