MyBatisPlus从入门到精通

1. 概述

MybatisPlus是一款Mybatis增强工具，用于简化开发，提高效率。 它在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

官网：https://baomidou.com/

2.快速入门

2.0 准备工作

①准备数据

CREATE TABLE `user` (
`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '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',
`address` varchar(100) DEFAULT NULL COMMENT '地址',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

insert into `user`(`id`,`user_name`,`password`,`name`,`age`,`address`) values
(1,'ruiwen','123','瑞文',12,'山东'),(2,'gailun','1332','盖伦',13,'平顶山'),
(3,'timu','123','提姆',22,'蘑菇石'),(4,'daji','1222','妲己',221,'狐山');

②创建SpringBoot工程

添加依赖

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.5.0</version>
</parent>
<dependencies>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>
</dependencies>

创建启动类

@SpringBootApplication
public class SGApplication {
    public static void main(String[] args) {
        SpringApplication.run(SGApplication.class);
    }
}

③准备实体类

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String address;
}

2.1 使用MybatisPlus

①添加依赖

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.4.3</version>
</dependency>

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

②配置数据库信息

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

③创建Mapper接口

创建Mapper接口继承BaseMapper接口

public interface UserMapper extends BaseMapper<User> {
}

BaseMapper接口中已经提供了很多常用方法。所以我们只需要直接从容器中获取Mapper就可以进行操作了，不需要自己去编写Sql语句。

④配置Mapper扫描

在启动类上配置我们的Mapper在哪个包。

@SpringBootApplication
@MapperScan("com.sangeng.mapper")
public class SGApplication {
    public static void main(String[] args) {
        SpringApplication.run(SGApplication.class);
    }
}

⑤获取Mapper进行测试

@SpringBootTest
public class MPTest {

    @Autowired
    private UserMapper userMapper;

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