Mybatis-Plus 快速入门 SpringBoot 整合 Mybatis-Plus

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

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(type = IdType.AUTO)

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	Mabatis Plus set 主键，雪花算法实现 (用Long存)
INPUT	需要开发者手动赋值
ASSIGN_ID	Mabatis Plus 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(赋值无效, 仍然自增)

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用的多

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。

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 {
    // 返回乐观锁拦截器
    @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;
    // status 要和表中字段名一样
    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;
    }
// 和数据库字段对应
    @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

mapper 查询

mapper.selectList()

// 不加条件查询
//mapper.selectList(null);
// 设置条件用, 这里用 Wrapper 的实现类
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' 左模糊 右模糊
//        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));
//查询多个 id  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);
System.out.println(mapper.selectOne(wrapper));

分页查询

首先在 MybatisConfig 中添加 MybatisPlusInterceptor

@Bean
public MybatisPlusInterceptor paginationInterceptor() {
    MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
    // 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求  默认false
    // paginationInterceptor.setOverflow(false);
    // 设置最大单页限制数量，默认 500 条，-1 不受限制
    // paginationInterceptor.setLimit(500);
    // 开启 count 的 join 优化,只针对部分 left join
    //这是分页拦截器
    PaginationInnerInterceptor paginationInnerInterceptor = new PaginationInnerInterceptor();
    paginationInnerInterceptor.setOverflow(true);
    paginationInnerInterceptor.setMaxLimit(500L);
    mybatisPlusInterceptor.addInnerInterceptor(paginationInnerInterceptor);
    return mybatisPlusInterceptor;
}

分页查询代码

//构造分页参数
Page<User> page = new Page<>(pn, 2);
//调用page进行分页
Page<User> userPage = userService.page(page, null);
//        userPage.getRecords()
//        userPage.getCurrent()
//        userPage.getPages()
model.addAttribute("users",userPage);

自定义 SQL（多表关联查询）

在 mapper 中自定义了 sql 需要在 service 和 serviceImpl 实现

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<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

//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

//        //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);

UpdateWrapper<Employee> updateWrapper=new UpdateWrapper<>();
  //UpdateWrapper<Employee> updateWrapper2 = Wrappers.<Employee>update();
  Employee employee=new Employee();
  employee.setEmail("1234@qq.com");
  employee.setPhoneNumber("1234567");
  updateWrapper.eq("id",6);
  int affectRows=employeeMapper.update(employee,updateWrapper);
  if(affectRows>0){
    System.out.println("更新成功");
  }else{
    System.out.println("更新失败");
  }

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

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");
        // 注意 mysql 版本导致这里会不同
        dataSourceConfig.setDriverName("com.mysql.cj.jdbc.Driver");
        autoGenerator.setDataSource(dataSourceConfig);
        
        //全局配置
        GlobalConfig globalConfig = new GlobalConfig();
       // 拿到工程绝对路径 System.getProperty("user.dir")
        globalConfig.setOutputDir(System.getProperty("user.dir")+"/src/main/java");
        globalConfig.setOpen(false);
        globalConfig.setAuthor("yangyu");
        globalConfig.setServiceName("%sService");
        autoGenerator.setGlobalConfig(globalConfig);
        //包信息
        PackageConfig packageConfig = new PackageConfig();
        // 父包
        packageConfig.setParent("com.catplatform.mybatisplus");
        // 在当前包下创建新的包
        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();
        //只生成部分表的mapper service controller
      //  strategyConfig.setInclude("user", "seller");
        // 自动增加 lombok 注解
        strategyConfig.setEntityLombokModel(true);
       // 下划线改成驼峰
        strategyConfig.setNaming(NamingStrategy.underline_to_camel);
       // 下划线改成驼峰
        strategyConfig.setColumnNaming(NamingStrategy.underline_to_camel);
        autoGenerator.setStrategy(strategyConfig);

        autoGenerator.execute();
    }
}

修改 MapperScan

service

DepartmentService 继承IService
DepartmentServiceImpl 继承ServiceImpl类

@RunWith(SpringRunner.class)
@SpringBootTest
public class DepartmentServiceTest {
  
    @Autowired
    private DepartmentService departmentService;
  
    /**
     * 增
     */
    @Test
    public void save(){
        Department department=new Department();
        department.setName("洋芋");
        department.setRemark("123");
        boolean save = departmentService.save(department);
        System.out.println(save);
    }
  
    /**
     * 改
     */
    @Test
    public void updateById(){
        Department department=new Department();
        department.setId(9);
        department.setName("洋芋2");
        department.setRemark("1232");
        boolean save = departmentService.updateById(department);
        System.out.println(save);
    }
  
    /**
     * 删
     */
    @Test
    public void removeById(){
        boolean b = departmentService.removeById(9);
        System.out.println(b);
    }
  
    /**
     * 查
     */
    @Test
    public void list(){
        List<Department> list = departmentService.list();
        System.out.println(list);
    }
  
    /**
     * 批量增加
     */
    @Test
    public void saveBatch(){
        Department department1=new Department();
        department1.setName("洋芋1");
        department1.setRemark("1231");
  
        Department department2=new Department();
        department2.setName("洋芋2");
        department2.setRemark("1232");
  
        Department department3=new Department();
        department3.setName("洋芋3");
        department3.setRemark("1233");
  
        boolean b = departmentService.saveBatch(Arrays.asList(department1, department2, department3));
        System.out.println(b);
    }
  
    /**
     * 批量增加或者更新
     */
    @Test
    public void saveOrUpdateBatch(){
        Department department1=new Department();
        department1.setName("洋芋4");
        department1.setRemark("1234");
  
        Department department2=new Department();
        department2.setId(11);
        department2.setName("洋芋2x");
        department2.setRemark("1232x");
  
        boolean b = departmentService.saveOrUpdateBatch(Arrays.asList(department1, department2));
        System.out.println(b);
    }

Spring Boot + MyBatis Plus 打包应用，直接发布 阿里云 上云

package + 在 target 中 用命令行 java -jar xxxx.jar