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  • MybatisPlus学习笔记

    mybatis-plus快速上手

    1.创建maven工程

    2.添加pom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.example.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.example.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.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/mybatis?useUnicode=true&characterEncoding=UTF-8
    username: root
    password: 1qaz@WSX
#想在运行时打印sql日志
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

    6.启动类添加@MapperScan("mapper所在包")注解

    package com.example.mybatisplus;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

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

}

    7.测试

    package com.example.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 userMapper;

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

}

    常用注解

    注：默认通过entity名字与数据表名匹配，如果名字匹配不上需要添加注解映射

    @TableName

    映射数据库表名

    @Data
@TableName(value = "user")
public class UserEntity {

   private Integer id;
   private String name;
   private Integer age;

}

    @TableId

    设置主键映射，value属性是数据库主键字段名

    type属性设置主键类型，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，会把id返回给java对象,即使开发者赋id值也取数据库的
    NONE MybatisPlus(MP) set主键，雪花算法实现
    INPUT 需要开发者手动赋值(开发者没有赋值，则数据库自增方式)
    ASSIGN_ID MP分配id,Long、Integer、String，雪花算法
    ASSIGN_UUID 分配UUID,主键类型必须String

    @TableField

    字段映射，value属性是数据库字段名

    exist属性表示是否是数据库字段

    select属性表示是否查询该字段

    fill属性表示是否自动填充，将对象存入数据库的时候由MP自动给某些字段赋值，如create_time、update_time

    @Data
@TableName(value = "user")
public class UserEntity {

    @TableId(value = "id",type = IdType.ASSIGN_ID)
    private Long id;
    @TableField(value = "name")
    private String userName;
    @TableField(value = "age")
    private Integer age;
    @TableField(exist = false)
    private String gender;
    //驼峰和数据库下划线会自动转换
    @TableField(fill = FieldFill.INSERT)
    private Date createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
}

    fill填充的值需要创建处理器赋值

    package com.example.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字段保证数据的安全性，当修改数据的时候，会以version作为条件，满足条件才修改

    添加配置类：

    package com.example.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.通过注解方式完成枚举类映射

    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

    枚举类：（加@EnumValue注释）

    package com.example.mybatisplus.enums;

import com.baomidou.mybatisplus.annotation.EnumValue;

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

    @EnumValue
    private Integer code;
    private String msg;

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

}

    实体类：加枚举类型

    @Data
@TableName(value = "user")
public class UserEntity {

    @TableId(value = "id",type = IdType.ASSIGN_ID)
    private Long id;
    @TableField(value = "name")
    private String userName;
    @TableField(value = "age")
    private Integer age;
    @TableField(exist = false)
    private String gender;
    //驼峰和数据库下划线会自动转换
    @TableField(fill = FieldFill.INSERT)
    private Date createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
    @Version
    private Integer version;
    private StatusEnum status;
}

    application.yml

    mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  #枚举包扫描  
  type-enums-package: com.example.mybatisplus.enums

    这几步配置后，查询出来的结果如下：

    2.实现接口方式实现枚举类映射

    package com.example.mybatisplus.enums;

import com.baomidou.mybatisplus.annotation.EnumValue;
import com.baomidou.mybatisplus.core.enums.IEnum;

public enum AgeEnum implements IEnum<Integer> {
    ONE(1,"一岁"),
    TWO(2,"两岁");

    @EnumValue
    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

    实体类添加：

    @TableLogic
private Integer deleted;
    1. application.yml添加配置
    mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  #枚举包扫描
  type-enums-package: com.example.mybatisplus.enums
  global-config:
    db-config:
      logic-not-delete-value: 1
      logic-delete-value: 0

    CRUD

    这里的api可以去官网查看

    MyBatis Plus自动生成

    根据数据表生成实体类和Mapper、Service等...

    1. pom依赖
    <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>

    启动类

    package com.example.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://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8");
        dataSourceConfig.setUsername("root");
        dataSourceConfig.setPassword("1qaz@WSX");
        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("niuwang");
        autoGenerator.setGlobalConfig(globalConfig);
        //包信息
        PackageConfig packageConfig = new PackageConfig();
        packageConfig.setParent("com.example.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();
    }
}

    部分表生成：

    strategyConfig.setInclude("user","product");
    • 注：该知识点是在B站学习‘楠哥教你学java’的视频中学习到的，大家有兴趣可以去B站大牛站学习
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  • 原文地址：https://www.cnblogs.com/niuwang/p/15192894.html
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