Mybatis-plus

本文最后更新于:2021年3月31日 晚上

MyBatis Plus

国产的开源框架,基于 MyBatis

核心功能就是简化 MyBatis 的开发,提高效率。

MyBatis Plus 快速上手

Spring Boot(2.3.0) + MyBatis Plus(国产的开源框架,并没有接入到 Spring 官方孵化器中)

1、创建 Maven 工程

cAs0KO.png

2、pom.xml 引入 MyBatis Plus 的依赖

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<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.1.tmp</version>
</dependency>

3、创建实体类

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package com.southwind.mybatisplus.entity;

import lombok.Data;

@Data
public class User {
private Integer id;
private String name;
private Integer age;
}

4、创建 Mapper 接口

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package com.southwind.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.southwind.mybatisplus.entity.User;

public interface UserMapper extends BaseMapper<User> {

}

5、application.yml

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spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/db?useUnicode=true&characterEncoding=UTF-8
username: root
password: root
mybatis-plus:
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

6、启动类需要添加 @MapperScan(“mapper所在的包”),否则无法加载 Mppaer bean。

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package com.southwind.mybatisplus;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.southwind.mybatisplus.mapper")
public class MybatisplusApplication {

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

}

7、测试

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package com.southwind.mybatisplus.mapper;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class UserMapperTest {

@Autowired
private UserMapper mapper;

@Test
void test(){
mapper.selectList(null).forEach(System.out::println);
}

}

常用注解

@TableName

映射数据库的表名

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package com.southwind.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName(value = "user")
public class Account {
private Integer id;
private String name;
private Integer age;
}

@TableId

设置主键映射,value 映射主键字段名

type 设置主键类型,主键的生成策略,

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AUTO(0),
NONE(1),
INPUT(2),
ASSIGN_ID(3),
ASSIGN_UUID(4),
/** @deprecated */
@Deprecated
ID_WORKER(3),
/** @deprecated */
@Deprecated
ID_WORKER_STR(3),
/** @deprecated */
@Deprecated
UUID(4);
描述
AUTO 数据库自增
NONE MP set 主键,雪花算法实现
INPUT 需要开发者手动赋值
ASSIGN_ID MP 分配 ID,Long、Integer、String
ASSIGN_UUID 分配 UUID,Strinig

INPUT 如果开发者没有手动赋值,则数据库通过自增的方式给主键赋值,如果开发者手动赋值,则存入该值。

AUTO 默认就是数据库自增,开发者无需赋值。

ASSIGN_ID MP 自动赋值,雪花算法。

ASSIGN_UUID 主键的数据类型必须是 String,自动生成 UUID 进行赋值

@TableField

映射非主键字段,value 映射字段名

exist 表示是否为数据库字段 false,如果实体类中的成员变量在数据库中没有对应的字段,则可以使用 exist,VO、DTO

select 表示是否查询该字段

fill 表示是否自动填充,将对象存入数据库的时候,由 MyBatis Plus 自动给某些字段赋值,create_time、update_time

1、给表添加 create_time、update_time 字段

2、实体类中添加成员变量

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package com.southwind.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

import java.util.Date;

@Data
@TableName(value = "user")
public class User {
@TableId
private String id;
@TableField(value = "name",select = false)
private String title;
private Integer age;
@TableField(exist = false)
private String gender;
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
}

3、创建自动填充处理器

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package com.southwind.mybatisplus.handler;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;

import java.util.Date;

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
@Override
public void insertFill(MetaObject metaObject) {
this.setFieldValByName("createTime",new Date(),metaObject);
this.setFieldValByName("updateTime",new Date(),metaObject);
}

@Override
public void updateFill(MetaObject metaObject) {
this.setFieldValByName("updateTime",new Date(),metaObject);
}
}

@Version

标记乐观锁,通过 version 字段来保证数据的安全性,当修改数据的时候,会以 version 作为条件,当条件成立的时候才会修改成功。

version = 2

线程 1:update … set version = 2 where version = 1

线程2 :update … set version = 2 where version = 1

1、数据库表添加 version 字段,默认值为 1

2、实体类添加 version 成员变量,并且添加 @Version

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package com.southwind.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.*;
import lombok.Data;

import java.util.Date;

@Data
@TableName(value = "user")
public class User {
@TableId
private String id;
@TableField(value = "name",select = false)
private String title;
private Integer age;
@TableField(exist = false)
private String gender;
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
@Version
private Integer version;
}

3、注册配置类

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package com.southwind.mybatisplus.config;

import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyBatisPlusConfig {

@Bean
public OptimisticLockerInterceptor optimisticLockerInterceptor(){
return new OptimisticLockerInterceptor();
}

}

@EnumValue

1、通用枚举类注解,将数据库字段映射成实体类的枚举类型成员变量

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package com.southwind.mybatisplus.enums;

import com.baomidou.mybatisplus.annotation.EnumValue;

public enum StatusEnum {
WORK(1,"上班"),
REST(0,"休息");

StatusEnum(Integer code, String msg) {
this.code = code;
this.msg = msg;
}

@EnumValue
private Integer code;
private String msg;
}
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package com.southwind.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.*;
import com.southwind.mybatisplus.enums.StatusEnum;
import lombok.Data;

import java.util.Date;

@Data
@TableName(value = "user")
public class User {
@TableId
private String id;
@TableField(value = "name",select = false)
private String title;
private Integer age;
@TableField(exist = false)
private String gender;
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
@Version
private Integer version;
private StatusEnum status;
}

application.yml

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type-enums-package: 
com.southwind.mybatisplus.enums

2、实现接口

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package com.southwind.mybatisplus.enums;

import com.baomidou.mybatisplus.core.enums.IEnum;

public enum AgeEnum implements IEnum<Integer> {
ONE(1,"一岁"),
TWO(2,"两岁"),
THREE(3,"三岁");

private Integer code;
private String msg;

AgeEnum(Integer code, String msg) {
this.code = code;
this.msg = msg;
}

@Override
public Integer getValue() {
return this.code;
}
}

@TableLogic

映射逻辑删除

1、数据表添加 deleted 字段

2、实体类添加注解

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package com.southwind.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.*;
import com.southwind.mybatisplus.enums.AgeEnum;
import com.southwind.mybatisplus.enums.StatusEnum;
import lombok.Data;

import java.util.Date;

@Data
@TableName(value = "user")
public class User {
@TableId
private String id;
@TableField(value = "name",select = false)
private String title;
private AgeEnum age;
@TableField(exist = false)
private String gender;
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;
@Version
private Integer version;
@TableField(value = "status")
private StatusEnum statusEnum;
@TableLogic
private Integer deleted;
}

3、application.yml 添加配置

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global-config:
db-config:
logic-not-delete-value: 0
logic-delete-value: 1

查询

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//mapper.selectList(null);
QueryWrapper wrapper = new QueryWrapper();
// Map<String,Object> map = new HashMap<>();
// map.put("name","小红");
// map.put("age",3);
// wrapper.allEq(map);
// wrapper.gt("age",2);
// wrapper.ne("name","小红");
// wrapper.ge("age",2);

//like '%小'
// wrapper.likeLeft("name","小");
//like '小%'
// wrapper.likeRight("name","小");

//inSQL
// wrapper.inSql("id","select id from user where id < 10");
// wrapper.inSql("age","select age from user where age > 3");

// wrapper.orderByDesc("age");

// wrapper.orderByAsc("age");
// wrapper.having("id > 8");

mapper.selectList(wrapper).forEach(System.out::println);
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//        System.out.println(mapper.selectById(7));
// mapper.selectBatchIds(Arrays.asList(7,8,9)).forEach(System.out::println);

//Map 只能做等值判断,逻辑判断需要使用 Wrapper 来处理
// Map<String,Object> map = new HashMap<>();
// map.put("id",7);
// mapper.selectByMap(map).forEach(System.out::println);

QueryWrapper wrapper = new QueryWrapper();
wrapper.eq("id",7);
//// System.out.println(mapper.selectCount(wrapper));
//
// //将查询的结果集封装到Map中
// mapper.selectMaps(wrapper).forEach(System.out::println);
// System.out.println("-------------------");
// mapper.selectList(wrapper).forEach(System.out::println);

//分页查询
// Page<User> page = new Page<>(2,2);
// Page<User> result = mapper.selectPage(page,null);
// System.out.println(result.getSize());
// System.out.println(result.getTotal());
// result.getRecords().forEach(System.out::println);

// Page<Map<String,Object>> page = new Page<>(1,2);
// mapper.selectMapsPage(page,null).getRecords().forEach(System.out::println);

// mapper.selectObjs(null).forEach(System.out::println);


System.out.println(mapper.selectOne(wrapper));

自定义 SQL(多表关联查询)

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package com.southwind.mybatisplus.entity;

import lombok.Data;

@Data
public class ProductVO {
private Integer category;
private Integer count;
private String description;
private Integer userId;
private String userName;
}
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package com.southwind.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.southwind.mybatisplus.entity.ProductVO;
import com.southwind.mybatisplus.entity.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface UserMapper extends BaseMapper<User> {
@Select("select p.*,u.name userName from product p,user u where p.user_id = u.id and u.id = #{id}")
List<ProductVO> productList(Integer id);
}

添加

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User user = new User();
user.setTitle("小明");
user.setAge(22);
mapper.insert(user);
System.out.println(user);

删除

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//mapper.deleteById(1);
// mapper.deleteBatchIds(Arrays.asList(7,8));
// QueryWrapper wrapper = new QueryWrapper();
// wrapper.eq("age",14);
// mapper.delete(wrapper);

Map<String,Object> map = new HashMap<>();
map.put("id",10);
mapper.deleteByMap(map);

修改

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//        //update ... version = 3 where version = 2
// User user = mapper.selectById(7);
// user.setTitle("一号");
//
// //update ... version = 3 where version = 2
// User user1 = mapper.selectById(7);
// user1.setTitle("二号");
//
// mapper.updateById(user1);
// mapper.updateById(user);

User user = mapper.selectById(1);
user.setTitle("小红");
QueryWrapper wrapper = new QueryWrapper();
wrapper.eq("age",22);
mapper.update(user,wrapper);

MyBatisPlus 自动生成

根据数据表自动生成实体类、Mapper、Service、ServiceImpl、Controller

1、pom.xml 导入 MyBatis Plus Generator

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<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-generator</artifactId>
<version>3.3.1.tmp</version>
</dependency>

<dependency>
<groupId>org.apache.velocity</groupId>
<artifactId>velocity</artifactId>
<version>1.7</version>
</dependency>

Velocity(默认)、Freemarker、Beetl

2、启动类

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package com.southwind.mybatisplus;

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.generator.AutoGenerator;
import com.baomidou.mybatisplus.generator.config.DataSourceConfig;
import com.baomidou.mybatisplus.generator.config.GlobalConfig;
import com.baomidou.mybatisplus.generator.config.PackageConfig;
import com.baomidou.mybatisplus.generator.config.StrategyConfig;
import com.baomidou.mybatisplus.generator.config.rules.NamingStrategy;

public class Main {
public static void main(String[] args) {
//创建generator对象
AutoGenerator autoGenerator = new AutoGenerator();
//数据源
DataSourceConfig dataSourceConfig = new DataSourceConfig();
dataSourceConfig.setDbType(DbType.MYSQL);
dataSourceConfig.setUrl("jdbc:mysql://ip:3306/db?useUnicode=true&characterEncoding=UTF-8");
dataSourceConfig.setUsername("root");
dataSourceConfig.setPassword("root");
dataSourceConfig.setDriverName("com.mysql.cj.jdbc.Driver");
autoGenerator.setDataSource(dataSourceConfig);
//全局配置
GlobalConfig globalConfig = new GlobalConfig();
globalConfig.setOutputDir(System.getProperty("user.dir")+"/src/main/java");
globalConfig.setOpen(false);
globalConfig.setAuthor("southwind");
globalConfig.setServiceName("%sService");
autoGenerator.setGlobalConfig(globalConfig);
//包信息
PackageConfig packageConfig = new PackageConfig();
packageConfig.setParent("com.southwind.mybatisplus");
packageConfig.setModuleName("generator");
packageConfig.setController("controller");
packageConfig.setService("service");
packageConfig.setServiceImpl("service.impl");
packageConfig.setMapper("mapper");
packageConfig.setEntity("entity");
autoGenerator.setPackageInfo(packageConfig);
//配置策略
StrategyConfig strategyConfig = new StrategyConfig();
strategyConfig.setEntityLombokModel(true);
strategyConfig.setNaming(NamingStrategy.underline_to_camel);
strategyConfig.setColumnNaming(NamingStrategy.underline_to_camel);
autoGenerator.setStrategy(strategyConfig);

autoGenerator.execute();
}
}

来自:https://space.bilibili.com/434617924

https://mp.baomidou.com/


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