mybatis-plus学习记录（详细）

忘是亡心i 2022-11-29 11:25 67阅读 0赞

### 文章目录 ###

*  mybatis-plus
 *   *   *  MyBatis Plus 快速上手
         *  常用注解
         *   *  查询
         *  自定义 SQL（多表关联查询）
         *   *  添加
             *  删除
             *  修改
             *  MyBatisPlus自动生成
             *  Spring Boot +MyBatis Plus 打包，发布阿里云
         *  获取代码地址见下GitHub链接

# mybatis-plus #

官网：[https://mp.baomidou.com/guide/][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）

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaG1vbmtleQ_size_16_color_FFFFFF_t_70_pic_center]

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

### 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);

<table> 
 <thead> 
  <tr> 
   <th>值</th> 
   <th>描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>AUTO</td> 
   <td>数据库自增</td> 
  </tr> 
  <tr> 
   <td>NONE</td> 
   <td>MP set 主键，雪花算法实现（默认）</td> 
  </tr> 
  <tr> 
   <td>INPUT</td> 
   <td>需要开发者手动赋值</td> 
  </tr> 
  <tr> 
   <td>ASSIGN_ID</td> 
   <td>MP 分配 ID，Long、Integer、String</td> 
  </tr> 
  <tr> 
   <td>ASSIGN_UUID</td> 
   <td>分配 UUID，Strinig</td> 
  </tr> 
 </tbody> 
</table>

`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：

![在这里插入图片描述][2020081920550648.JPG_pic_center]

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：

![在这里插入图片描述][20200819205438444.JPG_pic_center]

#### Spring Boot +MyBatis Plus 打包，发布阿里云 ####

[参见楠哥视频][Link 1]

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][https_github.com_monkeyhlj_spring-study]

[https_mp.baomidou.com_guide]: https://mp.baomidou.com/guide/
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[20200819205438444.JPG_pic_center]: /images/20221124/59f4cfb74641428399b41f086f36c507.png
[Link 1]: https://www.bilibili.com/video/BV1yA411t782?p=7
[https_github.com_monkeyhlj_spring-study]: https://github.com/monkeyhlj/spring-study