mybatis-plus学习记录（详细）

mybatis-plus

官网：https://mp.baomidou.com/guide/

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）

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.monkey.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.monkey.mybatisplus;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.monkey.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/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    username: root
    password: 123456
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl   //打印sql日志

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

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

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

}

7、测试

package com.monkey.mybatisplus;

import com.monkey.mybatisplus.mapper.UserMapper;
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 userMapper;

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

}

常用注解

@TableName

映射数据库的表名（如果实体类名和数据库表名不一致）

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

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

@Data
public class User {
    @TableId(value = "id")
    private Integer num;
    private String name;
    private Integer age;
}

type 设置主键类型，主键的生成策略

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    @TableField(value = "name")
    private String title;
    private Integer age;
}

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（默认）
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，在VO、DTO用得较多。

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    @TableField(value = "name")
    private String title;
    private Integer age;
    @TableField(exist = false)
    private String gender;
}

select 表示是否查询该字段

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    @TableField(value = "name",select = false)
    private String title;
    private Integer age;
    @TableField(exist = false)
    private String gender;
}

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.monkey.mybatisplus.entity;

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

import java.util.Date;

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long 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;
//    private Product product;
}

3、创建自动填充处理器（自动填充时间-接上INSERT INSERT_UPDATE）

package com.monkey.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.monkey.mybatisplus.entity;

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

import java.util.Date;

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long 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  //乐观锁
    private Integer version;

//    private Product product;
}

3、注册配置类（让乐观锁生效）

package com.monkey.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();
    }
}

测试：

package com.monkey.mybatisplus;

import com.monkey.mybatisplus.mapper.UserMapper;
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 userMapper;

    @Test
    void test(){
        userMapper.selectList(null).forEach(System.out::println);
    }
    
    @Test
    void update(){
    	// update ... version = 3 where version = 2
    	User user = mapper.selectById(7);
    	user.setTitle("一号");
		
		// update ... version = 3 where version = 2
    	User user = mapper.selectById(7);
    	user.setTitle("二号");
		
		mapper.updateById(user1); //乐观锁保证修改只执行一次
		mapper.updateById(user);
    }

}

@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.monkey.mybatisplus.enums;

import com.baomidou.mybatisplus.annotation.EnumValue;

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

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

    @EnumValue
    private Integer code;
    private String msg;
}

package com.monkey.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.*;
import com.monkey.mybatisplus.enums.StatusEbum;
import lombok.Data;

import java.util.Date;

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long 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 StatusEbum status;

//    private Product product;
}

application.yml

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl   //打印sql日志
  type-enums-package: 
  	com.monkey.mybatisplus.enums  //扫描枚举的包

2、实现接口方式

package com.monkey.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（假删除）

1、数据表添加 deleted 字段

2、实体类添加注解

package com.monkey.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.*;
import com.monkey.mybatisplus.enums.AgeEnum;
import com.monkey.mybatisplus.enums.StatusEbum;
import lombok.Data;

import java.util.Date;

@Data
public class User {
    @TableId(type = IdType.AUTO)
    private Long id;
    @TableField(value = "name",select = false)
    private String title;
//    private AgeEnum age;
    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 StatusEbum status;
    @TableLogic
    private Integer deleted;

//    private Product product;
}

3、application.yml 添加配置

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

查询

    @Test
    void select(){
        //不加任何条件直接全部查询
//        userMapper.selectList(null);

        QueryWrapper wrapper = new QueryWrapper();
//        wrapper.eq("name","梅西2");

//        Map<String,Object> map = new HashMap<>();
//        map.put("name","梅西2");
//        map.put("age",18);
//        wrapper.allEq(map);

//        wrapper.lt("age",6);//小于
//        wrapper.gt("age",6);//大于
//        wrapper.ne("name","梅西2");//不等于
//        wrapper.ge("age",5);//大于等于

//        wrapper.like("name","西");//模糊查询
        //like '%西'
//        wrapper.likeLeft("name","西");//模糊查询
        //like '西%'
//        wrapper.likeRight("name","西");//模糊查询

        //inSQL联合查询
//        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");

        System.out.println(userMapper.selectList(wrapper));
}

    @Test
    void select2(){
//        System.out.println(userMapper.selectById(1));
//        userMapper.selectBatchIds(Arrays.asList(1,2,3).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",1);
//        userMapper.selectByMap(map);

//        QueryWrapper wrapper = new QueryWrapper();
//        wrapper.gt("id",1);
//        System.out.println(userMapper.selectCount(wrapper));
        //下面将查询的结果集封装到Map中
//        userMapper.selectMaps(wrapper).forEach(System.out::println);
//        userMapper.selectList(wrapper).forEach(System.out::println);

        //分页
//        Page<User> page = new Page<>(1,5);
//        Page<User> result = userMapper.selectPage(page, null);
//        System.out.println(result.getSize());
//        System.out.println(result.getTotal());
//        System.out.println(result.getRecords().forEach(System.out::println););

        //将结果封装到Map中
//        Page<Map<String,Object>> page = new Page<>(1,2); //第一页，每一页两条记录
//        userMapper.selectMapsPage(page,null).getRecords().forEach(System.out::println);

        //返回ids
//        userMapper.selectObjs(null).forEach(System.out::println);

        QueryWrapper wrapper = new QueryWrapper();
        wrapper.eq("id",1);
        System.out.println(userMapper.selectOne(wrapper));
    }

自定义 SQL（多表关联查询）

package com.monkey.mybatisplus.vo;

import lombok.Data;

@Data
public class ProductVo {
    private Integer category;
    private Integer count;
    private String description;
    private Integer userId;
    private String userName;
}

package com.monkey.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.monkey.mybatisplus.entity.User;
import com.monkey.mybatisplus.vo.ProductVo;
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);
}

@Test
void product(){
  userMapper.productList(1).forEach(System.out::println);
}

添加

@Test
void save(){
    User u = new User();
    u.setTitle("孙悟空");
    u.setAge(18);
    userMapper.insert(u);
    System.out.println(u);
}

删除

@Test
void delete(){
//        userMapper.deleteById(1);
//        userMapper.deleteBatchIds(Arrays.asList(1,2));

//        QueryWrapper wrapper = new QueryWrapper();
//        wrapper.eq("age",14);
//        userMapper.delete(wrapper);

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

修改

@Test
void update(){
//        User user = userMapper.selectById(1);
//        user.setTitle("梅西2");
//        userMapper.updateById(user);

//        //update ... version = 3 where version = 2
//        User user = mapper.selectById(1);
//        user.setTitle("一号");
//
//        //update ... version = 3 where version = 2
//        User user1 = mapper.selectById(1);
//        user1.setTitle("二号");
//
//        userMapper.updateById(user1);
//        userMapper.updateById(user);

    User user = userMapper.selectById(1);
    user.setTitle("小红");
    QueryWrapper wrapper = new QueryWrapper();
    wrapper.eq("age",18);
    userMapper.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

<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.monkey.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 Generator {
    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://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai");
        dataSourceConfig.setUsername("root");
        dataSourceConfig.setPassword("123456");
        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); //创建好之后不打开文件夹
        globalConfig.setAuthor("hhhmonkey");
        globalConfig.setServiceName("%sService");  //去掉Impl前面的I
        autoGenerator.setGlobalConfig(globalConfig); 

        //包信息
        PackageConfig packageConfig = new PackageConfig();
        packageConfig.setParent("com.monkey.mybatisplus");
        packageConfig.setModuleName("your");
        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.setInclude("user","product"); //默认生成所有表，这里设置只生成部分表
        strategyConfig.setInclude("user");
        strategyConfig.setEntityLombokModel(true); //自动添lombok注解
        strategyConfig.setNaming(NamingStrategy.underline_to_camel);
        strategyConfig.setColumnNaming(NamingStrategy.underline_to_camel); //驼峰命名
        autoGenerator.setStrategy(strategyConfig);

        autoGenerator.execute();
    }
}

运行Generator的main方法，可得到自动生成的代码结构如下图所示：

在UserController中写一个接口测试：

package com.monkey.mybatisplus.your.controller;


import com.monkey.mybatisplus.your.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.stereotype.Controller;
import org.springframework.web.servlet.ModelAndView;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author hhhmonkey
 * @since 2020-08-19
 */
@Controller
@RequestMapping("/your/user")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/index")
    public ModelAndView index(){
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("index");
        modelAndView.addObject("list",userService.list());
        return modelAndView;
    }

}

application.yml:

 thymeleaf:
    prefix: classpath:/templates/
    suffix: .html

index.html:

<!DOCTYPE html>
<html lang="en">
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <table>
        <tr th:each="user:${list}">
            <td th:text="${user.id}"></td>
            <td th:text="${user.name}"></td>
            <td th:text="${user.age}"></td>
        </tr>
    </table>

</body>
</html>

运行Spring boot应用：

在浏览器查看结果：

Spring Boot +MyBatis Plus 打包，发布阿里云

参见楠哥视频

本文是在视频学习过程中边学习边敲的，如有错误欢迎指正，阿里云部分可去学习B站楠哥教学视频，这里也顺便帮楠哥宣传一下，讲课辛苦了，感谢楠哥。

获取代码地址见下GitHub链接

（可参照代码看本篇文章，然后自己动手写，加油！）

github : https://github.com/monkeyhlj/spring-study