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.Driverurl: jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8username: rootpassword: 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@Testvoid show() {List<User> users = userMapper.selectList(null);System.out.println(users);}
}