1、准备开发环境

Idea：idea 2019.2
JDK：JDK8+
构建工具：maven 3.6.1
MySQL版本：MySQL 5.7
Spring Boot：2.6.3
MyBatis-Plus：3.5.1

2、创建数据库及表

（1）创建表

CREATE DATABASE `mybatis_plus`;
use `mybatis_plus`;
DROP TABLE IF EXISTS user;
CREATE TABLE `user` ( 
  `id` bigint(20) NOT NULL COMMENT '主键ID', 
  `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 DEFAULT CHARSET=utf8;

（2）添加数据

DELETE FROM user;
INSERT INTO user (id, name, age, email) VALUES 
(1, 'Jone', 18, 'test1@baomidou.com'), 
(2, 'Jack', 20, 'test2@baomidou.com'), 
(3, 'Tom', 28, 'test3@baomidou.com'), 
(4, 'Sandy', 21, 'test4@baomidou.com'), 
(5, 'Billie', 24, 'test5@baomidou.com');

3、创建Spring Boot工程

（1）初始化工程
使用 Spring Initializr 快速初始化一个 Spring Boot 工程

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（2）引入依赖

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.3</version>
        <relativePath/>
    </parent>

    <groupId>com.xilc</groupId>
    <artifactId>mybatis-plus-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <name>mybatis-plus-demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

（3）idea中安装lombok插件

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4、配置application.yml

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://192.168.1.30:3306/mybatis_plus?characterEncoding=utf-8&useSSL=false
    username: root
    password: root

注意：

1、驱动类driver-class-name
Spring Boot 2.0（内置jdbc5驱动），驱动类使用 com.mysql.jdbc.Driver
Spring Boot 2.1及以上（内置jdbc8驱动），驱动类使用 com.mysql.cj.jdbc.Driver
否则运行时候会有 WARN 信息

2、连接地址url
MySQL5.7版本的url：
jdbc:mysql://localhost:3306/mybatis_plus?characterEncoding=utf-8&useSSL=false
MySQL8.0版本的url：
jdbc:mysql://localhost:3306/mybatis_plus?
serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
否则运行测试用例报告如下错误：
java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more

5、创建启动类

在Spring Boot启动类中添加@MapperScan注解，扫描mapper包

@SpringBootApplication
@MapperScan("com.xilc.mybatisplus.mapper")
public class MybatisPlusApp {
    public static void main(String[] args) {
        SpringApplication.run(MybatisPlusApp.class, args);
    }
}

6、添加实体类

@Data
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

7、添加mapper

BaseMapper是MyBatis-Plus提供的模板mapper，其中包含了基本的CRUD方法，泛型为操作的实体类型

public interface UserMapper extends BaseMapper<User> {
    
}

8、测试

@SpringBootTest
class MybatisPlusTests {

    @Autowired
    UserMapper userMapper;
    @Test
    void testList() {
        List<User> list = userMapper.selectList(null);
        list.forEach(System.out::println);
    }
}

测试结果：

User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)

9、添加日志

在application.yml中配置日志输出

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

控制台打印效果：

==>  Preparing: SELECT id,name,age,email FROM user
==> Parameters: 
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, test1@baomidou.com
<==        Row: 2, Jack, 20, test2@baomidou.com
<==        Row: 3, Tom, 28, test3@baomidou.com
<==        Row: 4, Sandy, 21, test4@baomidou.com
<==        Row: 5, Billie, 24, test5@baomidou.com
<==      Total: 5