[大数据]MyBatis-Plus学习笔记1-入门

mp(MyBatis-Plus)是什么

????????Mybatis-Plus(简称MP)是一个Mybtis的增强工具,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,能快速地进行CRUD操作.

官网:https://mp.baomidou.com/

mp入门

1.创建数据库,创建数据库表,添加数据,用于mp操作

创建用户表

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)
)

插入数据

DELETE FROM user;

INSERT INTO user (id,name,age,email) VALUES
(1,'Icon',21,'test@163.com'),
(2,'Light',20,'test2@163.com'),
(3,'Lwx',20,'test3@163.com'),
(4,'Leyan',21,'test4@163.com'),
(5,'Theshy',21,'test5@163.com');

创建Springboot工程

引入依赖

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

数据库连接

1.Springboot 2.1以后数据库连接驱动类不用com.mysql.jdbc.Driver,用com.mysql.cj.jdbc.Driver

2.加上时区serverTimezone=GMT%2B8??? 东八区

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8
    username: root
    password: abc123

创建实体

@Data是lombok插件所提供的

package com.example.mpdemo.entity;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
//@Data自动生成get set方法
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

创建接口

继承mybatis_plus提供的BaseMapper,即可使用他的增删改查操作

package com.example.mpdemo.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.mpdemo.entity.User;
public interface UserMapper extends BaseMapper<User> {
}

在启动类中加个MapperScan,让它扫描到接口

package com.example.mpdemo;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@MapperScan("com.example.mpdemo.mapper")
public class MpdemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(MpdemoApplication.class, args);
    }

}

?测试

package com.example.mpdemo;
import com.example.mpdemo.entity.User;
import com.example.mpdemo.mapper.UserMapper;
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 MpdemoApplicationTests {
    @Autowired//自动注入
    private UserMapper userMapper;
    //查询user所有数据
    @Test
     void show() {
        List<User> users = userMapper.selectList(null);
        System.out.println(users);
    }
}