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
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2、pom.xml 引入 MyBatis Plus 的依赖
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.1.tmp</version>
</dependency>
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<User> {
}
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
ID_WORKER(3),
@Deprecated
ID_WORKER_STR(3),
@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;@Componentpublic 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;@Configurationpublic 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<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
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
自定义 SQL（多表关联查询）
package com.southwind.mybatisplus.entity;import lombok.Data;@Datapublic 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<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
User user = new User();user.setTitle("小明");user.setAge(22);mapper.insert(user);System.out.println(user);
删除
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);
分页
- 配置
@Configurationpublic class MybatisPlusConfig { @Bean public MybatisPlusInterceptor mybatisPlusInterceptor() { MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor(); interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2)); return interceptor; }}
-
dao层
@Select("${uid}")
page参数详解(源码)
protected List<T> records = Collections.emptyList();protected long total = 0;protected long size = 10;protected long current = 1;
ps:
比如我要查limit 0,3 3,3
page.setSize(3)
page.setcurrent(“当前是该第几页了”) // 比如 1 为0,3
缓存
//使用注解方式开启二级缓存
在dao上加注解
@CacheNamespace(blocking = true)
public interface TestDao extends BaseMapper<Test> { @Select("SELECT * from test,test2 where test.id = test2.f_id and test.id = #{id}")
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
<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
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) {
Spring Boot + MyBatis Plus 打包应用，直接发布 阿里云 上云
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