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
maven.png
2、pom.xml 引入 MyBatis Plus 的依赖
com.baomidou
mybatis-plus-boot-starter
3.3.1.tmp
3、创建实体类
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
package com.southwind.mybatisplus.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.southwind.mybatisplus.entity.User;
public interface UserMapper extends BaseMapper {
}
5、application.yml
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。
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
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
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，
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);
| 值 | 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
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
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
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
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
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;
}
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
type-enums-package:
com.southwind.mybatisplus.enums
2、实现接口
package com.southwind.mybatisplus.enums;
import com.baomidou.mybatisplus.core.enums.IEnum;
public enum AgeEnum implements IEnum {
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
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
global-config:
db-config:
logic-not-delete-value: 0
logic-delete-value: 1
查询
//mapper.selectList(null);
QueryWrapper wrapper = new QueryWrapper();
// Map 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);
// 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 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 page = new Page<>(2,2);
// Page result = mapper.selectPage(page,null);
// System.out.println(result.getSize());
// System.out.println(result.getTotal());
// result.getRecords().forEach(System.out::println);
// Page> 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）
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;
}
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 {
@Select("select p.*,u.name userName from product p,user u where p.user_id = u.id and u.id = #{id}")
List productList(Integer id);
}
添加
User user = new User();
user.setTitle("小明");
user.setAge(22);
mapper.insert(user);
System.out.println(user);
删除
//mapper.deleteById(1);
// mapper.deleteBatchIds(Arrays.asList(7,8));
// QueryWrapper wrapper = new QueryWrapper();
// wrapper.eq("age",14);
// mapper.delete(wrapper);
Map map = new HashMap<>();
map.put("id",10);
mapper.deleteByMap(map);
修改
// //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
com.baomidou
mybatis-plus-generator
3.3.1.tmp
org.apache.velocity
velocity
1.7
Velocity（默认）、Freemarker、Beetl
2、启动类
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