MyBatisPlus教程

一、MyBatisPlus

KuangStudy

MyBatisPlus学习视频:狂神说MyBatisPlus教程

KuangStudy
https://www.kuangstudy.com/course

MyBatisPlus学习视频:
https://www.bilibili.com/video/BV17E411N7KN?p=1

MyBatisPlus官网:https://baomidou.com/

MyBatisPlus文档:https://baomidou.com/pages/24112f/

一、MyBatisPlus简介

一、MyBatisPlus简介

MyBatisPlus官网:https://baomidou.com/

MyBatisPlus文档:https://baomidou.com/pages/24112f/

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二、特性

  • 无侵入:只做增强不做改变,引入它不会对现有工程产生影响,如丝般顺滑
  • 损耗小:启动即会自动注入基本 CURD,性能基本无损耗,直接面向对象操作
  • 强大的 CRUD 操作:内置通用 Mapper、通用 Service,仅仅通过少量配置即可实现单表大部分 CRUD 操作,更有强大的条件构造器,满足各类使用需求
  • 支持 Lambda 形式调用:通过 Lambda 表达式,方便的编写各类查询条件,无需再担心字段写错
  • 支持主键自动生成:支持多达 4 种主键策略(内含分布式唯一 ID 生成器 - Sequence),可自由配置,完美解决主键问题
  • 支持 ActiveRecord 模式:支持 ActiveRecord 形式调用,实体类只需继承 Model 类即可进行强大的 CRUD 操作
  • 支持自定义全局通用操作:支持全局通用方法注入( Write once, use anywhere )
  • 内置代码生成器:采用代码或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、 Controller 层代码,支持模板引擎,更有超多自定义配置等您来使用
  • 内置分页插件:基于 MyBatis 物理分页,开发者无需关心具体操作,配置好插件之后,写分页等同于普通 List 查询
  • 分页插件支持多种数据库:支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、SQLServer 等多种数据库
  • 内置性能分析插件:可输出 SQL 语句以及其执行时间,建议开发测试时启用该功能,能快速揪出慢查询
  • 内置全局拦截插件:提供全表 delete 、 update 操作智能分析阻断,也可自定义拦截规则,预防误操作

二、快速入门

使用第三方插件:

  1. 导入对应的依赖
  2. 研究依赖如何配置
  3. 代码如何编写
  4. 提高扩展技术能力

1.创建数据库 mybatis_plus

DROP TABLE IF EXISTS user;

CREATE TABLE user
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);
--真实开发环境中,version(乐观锁),deleted(逻辑删除),gmt_create,gmt_modified
DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, '[email protected]'),
(2, 'Jack', 20, '[email protected]'),
(3, 'Tom', 28, '[email protected]'),
(4, 'Sandy', 21, '[email protected]'),
(5, 'Billie', 24, '[email protected]');

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2、编写项目,使用SpringBoot初始化!

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3、 导入依赖

注:我们使用mybatis-plus 可以节省我们大量的代码,尽量不要同时导入mybatis和mybatis-plus因为版本有差异!
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.Jin</groupId>
    <artifactId>mybatis_plus</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis_plus</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <!--数据库驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.22</version>
        </dependency>
        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.16</version>
        </dependency>
        <!--mybatis_plus是自己开发的,并非官方的-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.0.5</version>
        </dependency>
        <!-- 代码生成器模板引擎 -->
        <dependency>
            <groupId>org.apache.velocity</groupId>
            <artifactId>velocity-engine-core</artifactId>
            <version>2.0</version>
        </dependency>
        <dependency>
            <groupId>hu.blackbelt.bundles.swagger-parser</groupId>
            <artifactId>io.swagger.parser</artifactId>
            <version>1.0.47_1</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

4、application.properties配置文件

#设置开发环境
spring.profiles.active=dev
#mysql 8
spring.datasource.username=root
spring.datasource.password=123456
#spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?useUnicode=true&characterEncoding=UTF-8&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC
#serverTimezone=Asia/Shanghai        serverTimezone=GMT%2B8
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?useSSL=false&useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
#配置日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
#逻辑删除配置
mybatis-plus.global-config.db-config.logic-delete-value=1
mybatis-plus.global-config.db-config.logic-not-delete-value=0

5、编写pojo

package com.jin.pojo;

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

import java.util.Date;

/**
 * @Package:com.jin.pojo
 * @ClassName: User
 * @Description:
 * @Date: 2021/12/06 17:12
 * @Author: Jin
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
@TableName("user")
public class User {
    
    
    /**
     * Auto	            数据库自增
     * Input	        自行输入
     * ID_Worker	    分布式全局唯一ID 长整型类型
     * UUID	3           2位UUID字符串、全局唯一id uuid
     * NONE	            无状态
     * ID_WORKER_STR	分布式全局唯一ID 字符串类型
     */
    @TableId(type = IdType.AUTO)
    private Long id;
    private String name;
    private Integer age;
    private String email;

    @Version//乐观锁Version注解
    private Integer version;

    @TableLogic//逻辑删除注解
    private Integer deleted;

    //字段添加填充内容
    @TableField(fill = FieldFill.INSERT)
    private Date createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
}

6、编写mapper

package com.jin.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.jin.pojo.User;
import org.springframework.stereotype.Repository;

/**
 * @Package:com.jin.mapper
 * @ClassName: Usermapper
 * @Description:
 * @Date: 2021/12/06 17:14
 * @Author: Jin
 */
@Repository//代表持久层
//在mybatis_plus上面继承基本的类BaseMapper
public interface UserMapper extends BaseMapper<User> {
    
    

}

7、启动类配置

package com.jin;

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

//扫描mapper文件夹
@MapperScan("com.Jin.mapper")
@SpringBootApplication
public class MybatisPlusApplication {
    
    

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

}

8、测试

package com.jin;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.jin.mapper.UserMapper;
import com.jin.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@SpringBootTest
class MybatisPlusApplicationTests {
    
    

    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads() {
    
    
        List<User> users = userMapper.selectList(null);
        for (User user : users) {
    
    
            System.out.println(user);
        }
        System.out.println();
        users.forEach(System.out::println);
    }
}

9、输出结果

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三、配置日志

properties里配置日志

#配置日志
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

四、MyMetaObjectHandler

package com.jin.handler;

import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.reflection.MetaObject;
import org.springframework.stereotype.Component;

import java.util.Date;

/**
 * @Package:com.jin.handler
 * @ClassName: MyMetaObjectHandler
 * @Description:	处理器,自动填充插入和更新时间
 * @Date: 2021/12/07 9:20
 * @Author: Jin
 */
@Slf4j
@Component //把处理器加到IOC容器中
public class MyMetaObjectHandler implements MetaObjectHandler {
    
    
    //插入时的填充策略
    @Override
    public void insertFill(MetaObject metaObject) {
    
    
        log.info("start insert fill...");
        //    default MetaObjectHandler setFieldValByName(String fieldName, Object fieldVal, MetaObject metaObject) {
    
    
        this.setFieldValByName("createTime",new Date(),metaObject);
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }
    //更新时的填充策略
    @Override
    public void updateFill(MetaObject metaObject) {
    
    
        log.info("start update fill...");
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }
}

五、MyBatisPlusConfig

package com.jin.config;

import com.baomidou.mybatisplus.core.injector.ISqlInjector;
import com.baomidou.mybatisplus.extension.injector.LogicSqlInjector;
import com.baomidou.mybatisplus.extension.plugins.OptimisticLockerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PerformanceInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;
import org.springframework.transaction.annotation.EnableTransactionManagement;

/**
 * @Package:com.jin.config
 * @ClassName: MyBatisPlusConfig
 * @Description:
 * @Date: 2021/12/07 9:51
 * @Author: Jin
 */
//扫描我们的mapper文件夹
@MapperScan("com.Jin.mapper")
@EnableTransactionManagement
@Configuration               //配置类
public class MyBatisPlusConfig {
    
    
    /**
     * 旧版
     * //注册乐观锁插件
     */
    @Bean
    public OptimisticLockerInterceptor optimisticLockerInterceptor() {
    
    
        return new OptimisticLockerInterceptor();
    }
    /**
     * 旧版
     * 分页插件
     */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
    
    
        return new PaginationInterceptor();
    }
    /**
     * 旧版
     * 逻辑删除组件
     */
    @Bean
    public ISqlInjector sqlInjector(){
    
    
        return new LogicSqlInjector();
    }
    /**
     * 性能分析插件
     */
    @Bean
    @Profile({
    
    "dev","test"}) //设置dev 和 test环境开启,保障开发效率
    public PerformanceInterceptor performanceInterceptor(){
    
    
        PerformanceInterceptor performanceInterceptor = new PerformanceInterceptor();
        //设置sql执行的最大时间,如果超过就不执行(报错,提示sql执行时间too large),不允许用户等待
        performanceInterceptor.setMaxTime(200);
        //是否格式化代码
        performanceInterceptor.setFormat(true);
        return performanceInterceptor;
    }
}

六、MybatisPlusApplicationTests

package com.jin;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.jin.mapper.UserMapper;
import com.jin.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@SpringBootTest
class MybatisPlusApplicationTests {
    
    

    @Autowired
    private UserMapper userMapper;
	//查询所有数据
    @Test
    void contextLoads() {
    
    
        List<User> users = userMapper.selectList(null);
        for (User user : users) {
    
    
            System.out.println(user);
        }
        System.out.println();
        users.forEach(System.out::println);
    }
    //测试插入
    @Test
    public void insert(){
    
    
        User user = new User();
        user.setName("Yangon");
        user.setAge(11);
        user.setEmail("[email protected]");
        int insert = userMapper.insert(user);
        System.out.println(insert);
        System.out.println(user);
    }
    //测试更新
    @Test
    public void update(){
    
    
        User user = new User();
        user.setId(1L);
        user.setName("JiWu");
        user.setAge(99);
        int i = userMapper.updateById(user);
        System.out.println(i);
        System.out.println(user);
    }
    //测试乐观锁成功!
    @Test
    public void testOptimisticLocker(){
    
    
        //1、查询用户信息
        User user = userMapper.selectById(1L);
        System.out.println(user);
        //2、修改用户信息
        user.setName("Nameddd");
        user.setEmail("[email protected]");
        //3、执行更新操作
        userMapper.updateById(user);
    }
    //测试乐观锁失败!多线程下
    @Test
    public void testOptimisticLocker2(){
    
    
        //线程1
        User user = userMapper.selectById(1L);
        System.out.println(user);
        user.setName("Nameddd");
        user.setEmail("[email protected]");
        //模拟另外一个线程执行了插队操作
        User user2 = userMapper.selectById(1L);
        System.out.println(user);
        user2.setName("Nameddd2222");
        user2.setEmail("[email protected]");
        userMapper.updateById(user2);
        //自旋锁来多次尝试提交!
        userMapper.updateById(user);//如果没有乐观锁就会覆盖插队线程的值!
    }

    //测试按id查询
    @Test
    public void testSelectById(){
    
    
        User user = userMapper.selectById(1L);
        System.out.println(user);
    }
    //测试按批量查询
    @Test
    public void testSelectBatchId(){
    
    
        List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2, 3));
        System.out.println(users);
        System.out.println();
        users.forEach(System.out::println);
    }

    //测试按条件map查询
    @Test
    public void testSelectByMap(){
    
    
        HashMap<String, Object> map = new HashMap<>();
        //自定义查询
        map.put("name","JiWu");
        map.put("email","[email protected]");
        List<User> users = userMapper.selectByMap(map);
        users.forEach(System.out::println);
    }

    //测试分页查询
    @Test
    public void testPage(){
    
    
        //参数一:当前页
        //参数二:页面大小
        Page<User> page = new Page<>(2,5);
        userMapper.selectPage(page,null);
        page.getRecords().forEach(System.out::println);
        System.out.println(page.getTotal());
    }

    //测试根据id删除记录
    @Test
    public void testDeleteById(){
    
    
        int i = userMapper.deleteById(1L);
        System.out.println(i);
    }
    //测试根据id批量删除记录
    @Test
    public void testDeleteBatchIds(){
    
    
        int i = userMapper.deleteBatchIds(Arrays.asList(1467789606408249346L, 1467789606408249347L, 1467789606408249348L, 1467789606408249349L));
        System.out.println(i);
    }
    //测试通过Map删除记录
    @Test
    public void testDeleteByMap(){
    
    
        HashMap<String, Object> map = new HashMap<>();
        map.put("id",1467789606408249351L);
        int i = userMapper.deleteByMap(map);
        System.out.println(i);
    }
}

七、WrapperTest

package com.jin;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.jin.mapper.UserMapper;
import com.jin.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;
import java.util.Map;

/**
 * @Package:com.jin
 * @ClassName: WrapperTest
 * @Description:
 * @Date: 2021/12/07 15:16
 * @Author: Jin
 */
@SpringBootTest
public class WrapperTest {
    
    
    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads() {
    
    
        //查询name!=null和并且邮箱不为空的用户,年龄大于等于12
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper
            .isNotNull("name")
            .isNotNull("email")
            .ge("age",12);
        userMapper.selectList(wrapper).forEach(System.out::println);
    }
    @Test
    void test2(){
    
    
        //查询名字JiWu
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //查询一个数据,出现多个结果使用List或者Map
        wrapper.eq("name","Tom");
        User user = userMapper.selectOne(wrapper);
        System.out.println(user);
    }
    @Test
    void test3(){
    
    
        //查询年龄在20~30岁之间的用户
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.between("age",20,30);
        Integer count = userMapper.selectCount(wrapper);
        System.out.println(count);
    }
    @Test
    void test4(){
    
    
        //查询名字里面不包含Ji
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.notLike("name","Ji")
            .likeRight("email","t");
        List<Map<String, Object>> maps = userMapper.selectMaps(wrapper);
        maps.forEach(System.out::println);
    }
    @Test
    void test5(){
    
    
        //查询联表
        //id在子查询中查出来
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.inSql("id","select id from user where id<3");
        List<Object> objects = userMapper.selectObjs(wrapper);
        objects.forEach(System.out::println);
    }
    @Test
    void test6(){
    
    
        //查询通过id进行排序
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.orderByDesc("id");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
}

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八、代码生成器

package com.jin;

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.IdType;
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.po.TableFill;
import com.baomidou.mybatisplus.generator.config.rules.DateType;
import com.baomidou.mybatisplus.generator.config.rules.NamingStrategy;

import java.util.ArrayList;

/**
 * @Package:com.jin
 * @ClassName: JinCode
 * @Description:代码自动生成器
 * @Date: 2021/12/07 16:17
 * @Author: Jin
 */
// 代码自动生成器
public class JinCode {
    
    
    public static void main(String[] args) {
    
    
        // 需要构建一个 代码自动生成器 对象
        AutoGenerator mpg = new AutoGenerator();

        // 配置策略
        // 1、全局配置
        GlobalConfig gc = new GlobalConfig();
        String projectPath = System.getProperty("user.dir");
        gc.setOutputDir(projectPath+"/src/main/java");
        gc.setAuthor("Jin"); gc.setOpen(false);
        gc.setFileOverride(false);

        // 是否覆盖
        gc.setServiceName("%sService");

        // 去Service的I前缀
        gc.setIdType(IdType.ID_WORKER);
        gc.setDateType(DateType.ONLY_DATE);
        gc.setSwagger2(true);
        mpg.setGlobalConfig(gc);

        //2、设置数据源
        DataSourceConfig dsc = new DataSourceConfig();
        dsc.setUrl("jdbc:mysql://localhost:3306/test? useSSL=false&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8");
        dsc.setDriverName("com.mysql.cj.jdbc.Driver");
        dsc.setUsername("root");
        dsc.setPassword("123456");
        dsc.setDbType(DbType.MYSQL); mpg.setDataSource(dsc);

        //3、包的配置
        PackageConfig pc = new PackageConfig();
        //只需要改实体类名字 和包名 还有 数据库配置即可
        pc.setModuleName("blog"); pc.setParent("com.Jin");
        pc.setEntity("entity"); pc.setMapper("mapper");
        pc.setService("service"); pc.setController("controller");
        mpg.setPackageInfo(pc);

        //4、策略配置
        StrategyConfig strategy = new StrategyConfig();
        strategy.setInclude("account","emp","dept");

        // 设置要映射的表名
        strategy.setNaming(NamingStrategy.underline_to_camel);
        strategy.setColumnNaming(NamingStrategy.underline_to_camel);
        strategy.setEntityLombokModel(true);

        // 自动lombok;
        strategy.setLogicDeleteFieldName("deleted");

        // 自动填充配置
        TableFill gmtCreate = new TableFill("gmt_create", FieldFill.INSERT);
        TableFill gmtModified = new TableFill("gmt_modified", FieldFill.INSERT_UPDATE);
        ArrayList<TableFill> tableFills = new ArrayList<>();
        tableFills.add(gmtCreate); tableFills.add(gmtModified);
        strategy.setTableFillList(tableFills);

        // 乐观锁
        strategy.setVersionFieldName("version");
        strategy.setRestControllerStyle(true);
        strategy.setControllerMappingHyphenStyle(true);

        // localhost:8080/hello_id_2
        mpg.setStrategy(strategy);
        mpg.execute(); //执行
    }
}

输出结果

1642412681888

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转载自blog.csdn.net/weixin_45207323/article/details/129671925