mybatis plus学习
入门流程
创建个数据库
1.创建数据库mybatis_plus及user表
| id | name | age | |
|---|---|---|---|
| 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 |
对应的数据库脚本如下：
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)
);
对应的数据库脚本如下：
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');
IDEA创建个SpringBoot项目
2.使用SpringBoot初始化一个项目
勾选初始SpringBoot项目：
- Lombok
- Spring Web
- Mybatis Framwork
- MySqL Driver
在pom下配置Mybatis-Plus配置
在pom文件<dependencies>下配置
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.4.0</version>
</dependency>
在Application下添加注释
@MapperScan(“com.example.demo.mapper”)
package com.example.demo;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@MapperScan("com.example.demo.mapper")
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
创建pojo及子项目User实体类加注释@Date
package com.example.demo.pojo;
import lombok.Data;
@Data
public class User {
private long id;
private String name;
private Integer age;
private String email;
}
创建mapper及子项目UserMapper接口并继承extends BaseMapper
package com.example.demo.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.demo.pojo.User;
import org.springframework.stereotype.Repository;
@Repository//表示它是一个持久层
public interface UserMapper extends BaseMapper<User> {
}
测试
package com.example.demo;
import com.example.demo.mapper.UserMapper;
import com.example.demo.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import java.sql.Wrapper;
import java.util.List;
@SpringBootTest
class DemoApplicationTests {
//继承了BaseMapper,所有的方法都来自父类
@Autowired
private UserMapper userMapper;
@Test
void contextLoads() {
//queryWrapper参数是一个条件构造器，这里先不设条件，用null值
//查询全部用户
List<User> users = userMapper.selectList(null);
users.forEach(System.out::println);
}
}
打印结果
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.6.1)
2021-12-02 15:24:13.061 INFO 12304 --- [ main] com.example.demo.DemoApplicationTests : Starting DemoApplicationTests using Java 1.8.0_121 on DESKTOP-IFA4B36 with PID 12304 (started by BZ in D:\IntelliJ IDEA 2021.2.1\demo)
2021-12-02 15:24:13.062 INFO 12304 --- [ main] com.example.demo.DemoApplicationTests : No active profile set, falling back to default profiles: default
_ _ |_ _ _|_. ___ _ | _
| | |\/|_)(_| | |_\ |_)||_|_\
/ |
3.4.0
2021-12-02 15:24:15.195 WARN 12304 --- [ main] c.b.m.core.metadata.TableInfoHelper : This primary key of "id" is primitive !不建议如此请使用包装类 in Class: "com.example.demo.pojo.User"
2021-12-02 15:24:15.338 INFO 12304 --- [ main] com.example.demo.DemoApplicationTests : Started DemoApplicationTests in 2.549 seconds (JVM running for 3.478)
2021-12-02 15:24:15.580 INFO 12304 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2021-12-02 15:24:15.725 INFO 12304 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)
2021-12-02 15:24:15.786 INFO 12304 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated...
2021-12-02 15:24:15.793 INFO 12304 --- [ionShutdownHook] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed.
Process finished with exit code 0
配置日志
日志可以看到sql的具体执行
#数据库连接配置
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#配置日志
> mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
测试查询
//测试插入
@Test
public void testInsert(){
User user=new User();
user.setName("倩倩");
user.setAge(20);
user.setEmail("1321473656@qq.com");
int insert = userMapper.insert(user);
System.out.println(insert);
System.out.println(user);
}
主键自增策略
id实体类包装成包装类型的Long,
> IdType=
> AUTO(0),//数据库id自增
> NONE(1),//未设置主键
> INPUT(2),//手动输入
> ID_WORKER(3), //默认的，全局唯一id
> ID_WORKER_STR(5),//ID_WORKER的字符串表示法
> UUID(4),//全局唯一id，UUid
>
测试更新
@Test
public void testUpdate(){
User user=new User();
user.setId(6L);//更新id为6的，类型为Long类型别忘了
user.setAge(10);
user.setEmail("1321473666@qq.com");
User setAge;
int i = userMapper.updateById(user);
System.out.println(i);
}
自动填充、更新时间
创建时间、修改时间，这些操作需要自动化更新 所有的数据库表：gmt_create、gmt_modified要配置。
1.在表中新增字段create_time、update_tim
2.在实体类同步一下
> import java.util.Date;
@Data
public class User {
@TableId(type = IdType.INPUT)
private Long id;
private String name;
private Integer age;
private String email;
private Date CreateTime;
private Date UpdateTime;
}
然后在实体类中加注解
@TableField(fill= FieldFill.INSERT)
private Date CreateTime;
@TableField(fill=FieldFill.INSERT_UPDATE)
private Date UpdateTime;
然后编写处理器处理这两个注解即可
package com.example.demo.handler;
import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;
import java.util.Date;
@Slf4j
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
//插入时的填充策略
@Override
public void insertFill(MetaObject metaObject) {
log.info("start insert fill ....");
this.setFieldValByName("createTime",new Date(),metaObject);
this.setFieldValByName("updateTime",new Date(),metaObject);
}
//更新时的填充策略
@Override
public void updateFill(MetaObject metaObject) {
log.info("start update fill ....");
this.setFieldValByName("updateTime",new Date(),metaObject);
}
}