MyBatisPlus快速开始

快速开始

步骤

创建数据库: mybatis
现有一张 User 表

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, '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');

初始化项目
创建一个springboot项目
导入依赖

<!--mybatis-plus-->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.0.5</version>
    </dependency>
    <!--mysql-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <!--lombok用来简化实体类-->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>

连接数据库
配置application.properties

useSSl=false&nuseUnicode=true&characterEncoding=utf-8
#mysql数据库连接
# mysql 5.0
spring.datasource .driver-class-name = com.mysql.jdbc.Driver
spring.datasource .url = jdbc：mysql：// localhost：3306 / mybatis_plus
spring.datasource .username = root
spring.datasource .password = 123456

# mysql 8.0
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc：mysql：// localhost：3306 / mybatis_plus ？serverTimezone = GMT％2B8&useSSl=false&nuseUnicode=true&characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=2322jiang

编写实体类

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

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

编写Mapper

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.fan.mybatisplus.pojo.User;
import org.springframework.stereotype.Repository;

// 在对应的Mapper上面继承基本的类 BaseMapper
@Repository // 代表持久层
public interface UserMapper extends BaseMapper<User> {
}

主函数扫描下

@MapperScan("com.fan.mybatisplus.mapper") // 扫描 mapper 文件夹
@SpringBootApplication
public class MybatisplusApplication {

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

}

测试

import com.fan.pojo.User;
import com.fan.pojo.mapper.UserMapper;
import org.apache.catalina.mbeans.UserMBean;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class MybatisPlusApplicationTests {

    // 继承了BaseMapper, 所有的方法都来自父类
    // 也可以编写自己的扩展方法!
    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads() {
        // 查询全部用户
        // 参数是一个Wrapper ,条件构造器.
        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }
}