Mybatis Plus入门体验

创建user表

现有一张 User 表，其表结构如下：

id	name	age	email
1	Jone	18	[email protected]
2	Jack	20	[email protected]
3	Tom	28	[email protected]
4	Sandy	21	[email protected]
5	Billie	24	[email protected]

其对应的数据库 Schema 脚本如下：

DROP TABLE IF EXISTS user;

CREATE TABLE user
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);

其对应的数据库 Data 脚本如下：

DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, '[email protected]'),
(2, 'Jack', 20, '[email protected]'),
(3, 'Tom', 28, '[email protected]'),
(4, 'Sandy', 21, '[email protected]'),
(5, 'Billie', 24, '[email protected]');

创建工程引入依赖

引入 spring-boot-starter、spring-boot-starter-test、mybatis-plus-boot-starter依赖：

<!-- 数据库驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>
<!-- mybatis-plus -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.0.5</version>
</dependency>

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

配置

在 application.yml 配置文件中添加MySql数据库的相关配置：

spring:
  datasource:
    #MySQL配置
    driverClassName:  com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT&allowPublicKeyRetrieval=true
    username: root
    password: 123456

在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 文件夹：

@MapperScan("com.jiuqi.mapper")
@SpringBootApplication
public class MybatisPlusApplication {
    
    

    public static void main(String[] args) {
    
    
        SpringApplication.run(MybatisPlusApplication.class, args);
    }

}

编码

编写实体类 User.java

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

编写Mapper类 UserMapper.java

@Repository
public interface UserMapper extends BaseMapper<User> {
    
    
}

开始使用

添加测试类，进行功能测试：

@SpringBootTest
class MybatisPlusApplicationTests {
    
    

    @Autowired
    private UserMapper userMapper;

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

}

UserMapper 中的 selectList() 方法的参数为 MP 内置的条件封装器 Wrapper，所以不填写就是无任何条件

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