目录

• 一、mybatis-plus简介：
• 二、springboot整合mybatis-plus案例
• mybatis plus强大的条件构造器queryWrapper、updateWrapper
• 总结

一、mybatis-plus简介：

Mybatis-Plus（简称MP）是一个 Mybatis 的增强工具，在 Mybatis 的基础上只做增强不做改变，为简化开发、提高效率而生。这是官方给的定义，关于mybatis-plus的更多介绍及特性，可以参考mybatis-plus官网。那么它是怎么增强的呢？其实就是它已经封装好了一些crud方法，我们不需要再写xml了，直接调用这些方法就行，就类似于JPA。并且3.X系列支持lambda语法,让我在写条件构造的时候少了很多的"魔法值",从代码结构上更简洁了.

二、springboot整合mybatis-plus案例

pom.xml配置

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<dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <!--springboot程序测试依赖，如果是自动创建项目默认添加-->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.16.10</version>
      <scope>provided</scope>
    </dependency>
    <!-- 包含spirng Mvc ,tomcat的包包含requestMapping restController 等注解 -->
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid-spring-boot-starter</artifactId>
      <version>1.1.10</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <!-- druid依赖 -->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.1.0</version>
    </dependency>
    <!-- mybatisPlus 核心库 -->
    <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.1.0</version>
    </dependency>
  </dependencies>

application.yml配置

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server:
  port: 10100   #  配置启动端口号
 
mybatis:
  config-location: classpath:mybatis.cfg.xml    #  mybatis主配置文件所在路径
  type-aliases-package: com.demo.drools.entity  #  定义所有操作类的别名所在包
  mapper-locations:                                     #  所有的mapper映射文件
    - classpath:mapper/*.xml
 
spring: #springboot的配置
  datasource: #定义数据源
    #127.0.0.1为本机测试的ip，3306是mysql的端口号。serverTimezone是定义时区，照抄就好，mysql高版本需要定义这些东西
    #useSSL也是某些高版本mysql需要问有没有用SSL连接
    url: jdbc:mysql://127.0.0.1:3306/test?serverTimezone=GMT%2B8&useSSL=FALSE
    username: root  #数据库用户名，root为管理员
    password: 123456 #该数据库用户的密码
    # 使用druid数据源
    type: com.alibaba.druid.pool.DruidDataSource
 
# mybatis-plus相关配置
mybatis-plus:
  # xml扫描，多个目录用逗号或者分号分隔（告诉 Mapper 所对应的 XML 文件位置）
  mapper-locations: classpath:mapper/*.xml
  # 以下配置均有默认值,可以不设置
  global-config:
    db-config:
      #主键类型 AUTO:"数据库ID自增" INPUT:"用户输入ID",ID_WORKER:"全局唯一ID (数字类型唯一ID)", UUID:"全局唯一ID UUID";
      id-type: auto
      #字段策略 IGNORED:"忽略判断"  NOT_NULL:"非 NULL 判断")  NOT_EMPTY:"非空判断"
      field-strategy: NOT_EMPTY
      #数据库类型
      db-type: MYSQL
  configuration:
    # 是否开启自动驼峰命名规则映射:从数据库列名到Java属性驼峰命名的类似映射
    map-underscore-to-camel-case: true
    # 如果查询结果中包含空值的列，则 MyBatis 在映射的时候，不会映射这个字段
    call-setters-on-nulls: true
    # 这个配置会将执行的sql打印出来，在开发或测试的时候可以用
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

用户信息实体

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package com.demo.drools.entity;
 
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:14
 */
@Data
@TableName("user_info")//@TableName中的值对应着表名
public class UserInfoEntity {
    /**
     * 主键
     * @TableId中可以决定主键的类型,不写会采取默认值,默认值可以在yml中配置
     * AUTO: 数据库ID自增
     * INPUT: 用户输入ID
     * ID_WORKER: 全局唯一ID，Long类型的主键
     * ID_WORKER_STR: 字符串全局唯一ID
     * UUID: 全局唯一ID，UUID类型的主键
     * NONE: 该类型为未设置主键类型
     */
    @TableId(type = IdType.AUTO)
    private Long id;
    /**
     * 姓名
     */
    private String name;
    /**
     * 年龄
     */
    private Integer age;
    /**
     * 技能
     */
    private String skill;
    /**
     * 评价
     */
    private String evaluate;
    /**
     * 分数
     */
    private Long fraction;
}

config类

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package com.demo.drools.config;
 
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import com.baomidou.mybatisplus.extension.plugins.PerformanceInterceptor;
import org.springframework.context.annotation.Bean;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:14
 */
public class MybatisPlusConfig {
    /**
     * mybatis-plus SQL执行效率插件【生产环境可以关闭】
     */
    @Bean
    public PerformanceInterceptor performanceInterceptor() {
        return new PerformanceInterceptor();
    }
    /**
     * 分页插件
     */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }
}

spring boot启动类

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package com.demo.drools;
 
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
 
/**
 * @author 于嘉琪
 */
@SpringBootApplication
//@MapperScan和dao层添加@Mapper注解意思一样
@MapperScan(basePackages = "com.demo.drools.dao")
public class DroolsApplication {
    public static void main(String[] args) {
        SpringApplication.run(DroolsApplication.class, args);
    }
}

dao层

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package com.demo.drools.dao;
 
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.demo.drools.entity.UserInfoEntity;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
 
/**
 * 用户信息DAO
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:16
 */
@Mapper
public interface UserInfoDao extends BaseMapper<UserInfoEntity> {
   
}

service层

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package com.demo.drools.service;
 
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.service.IService;
import com.demo.drools.entity.UserInfoEntity;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:17
 */
public interface UserInfoService extends IService<UserInfoEntity> {
    
}

serviceImpl实现类层

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package com.demo.drools.service.impl;
 
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.demo.drools.dao.UserInfoDao;
import com.demo.drools.entity.UserInfoEntity;
import com.demo.drools.service.UserInfoService;
import org.springframework.stereotype.Service;
 
import javax.annotation.Resource;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:18
 */
@Service
public class UserInfoSerivceImpl extends ServiceImpl<UserInfoDao, UserInfoEntity> implements UserInfoService {
    
}

controller控制层

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package com.demo.drools.controller;
 
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.demo.drools.entity.UserInfoEntity;
import com.demo.drools.service.UserInfoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
 
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:28
 */
public class UserInfoPlusController {
    @Autowired
    private UserInfoService userInfoService;
    
    /**
     * MP扩展演示
     * @Author Sans
     * @CreateTime 2019/6/8 16:37
     * @Return Map<String,Object> 返回数据
     */
    @RequestMapping("/getInfoListPlus")
    public Map<String,Object> getInfoListPage(){
        //初始化返回类
        Map<String,Object> result = new HashMap<>();
        //查询年龄等于18岁的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE age = 18
        QueryWrapper<UserInfoEntity> queryWrapper1 = new QueryWrapper<>();
        queryWrapper1.lambda().eq(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList1 = userInfoService.list(queryWrapper1);
        result.put("studentAge18",userInfoEntityList1);
        //查询年龄大于5岁的学生且小于等于18岁的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE age > 5 AND age <= 18
        QueryWrapper<UserInfoEntity> queryWrapper2 = new QueryWrapper<>();
        queryWrapper2.lambda().gt(UserInfoEntity::getAge,5);
        queryWrapper2.lambda().le(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList2 = userInfoService.list(queryWrapper2);
        result.put("studentAge5",userInfoEntityList2);
        //模糊查询技能字段带有"画"的数据,并按照年龄降序
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE skill LIKE '%画%' ORDER BY age DESC
        QueryWrapper<UserInfoEntity> queryWrapper3 = new QueryWrapper<>();
        queryWrapper3.lambda().like(UserInfoEntity::getSkill,"画");
        queryWrapper3.lambda().orderByDesc(UserInfoEntity::getAge);
        List<UserInfoEntity> userInfoEntityList3 = userInfoService.list(queryWrapper3);
        result.put("studentAgeSkill",userInfoEntityList3);
        //模糊查询名字带有"小"或者年龄大于18的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE name LIKE '%小%' OR age > 18
        QueryWrapper<UserInfoEntity> queryWrapper4 = new QueryWrapper<>();
        queryWrapper4.lambda().like(UserInfoEntity::getName,"小");
        queryWrapper4.lambda().or().gt(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList4 = userInfoService.list(queryWrapper4);
        result.put("studentOr",userInfoEntityList4);
        //查询评价不为null的学生,并且分页
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE evaluate IS NOT NULL LIMIT 0,5
        IPage<UserInfoEntity> page = new Page<>();
        page.setCurrent(1);
        page.setSize(5);
        QueryWrapper<UserInfoEntity> queryWrapper5 = new QueryWrapper<>();
        queryWrapper5.lambda().isNotNull(UserInfoEntity::getEvaluate);
        page = userInfoService.page(page,queryWrapper5);
        result.put("studentPage",page);
        return result;
    }
}

controller层用到lambda语法

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package com.demo.drools.controller;
 
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.demo.drools.entity.UserInfoEntity;
import com.demo.drools.service.UserInfoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
 
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
/**
 * TODO your comment
 *
 * @author Yujiaqi
 * @date 2020/12/2 19:28
 */
public class UserInfoPlusController {
    @Autowired
    private UserInfoService userInfoService;
    
    /**
     * MP扩展演示
     * @Author Sans
     * @CreateTime 2019/6/8 16:37
     * @Return Map<String,Object> 返回数据
     */
    @RequestMapping("/getInfoListPlus")
    public Map<String,Object> getInfoListPage(){
        //初始化返回类
        Map<String,Object> result = new HashMap<>();
        //查询年龄等于18岁的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE age = 18
        QueryWrapper<UserInfoEntity> queryWrapper1 = new QueryWrapper<>();
        queryWrapper1.lambda().eq(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList1 = userInfoService.list(queryWrapper1);
        result.put("studentAge18",userInfoEntityList1);
        //查询年龄大于5岁的学生且小于等于18岁的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE age > 5 AND age <= 18
        QueryWrapper<UserInfoEntity> queryWrapper2 = new QueryWrapper<>();
        queryWrapper2.lambda().gt(UserInfoEntity::getAge,5);
        queryWrapper2.lambda().le(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList2 = userInfoService.list(queryWrapper2);
        result.put("studentAge5",userInfoEntityList2);
        //模糊查询技能字段带有"画"的数据,并按照年龄降序
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE skill LIKE '%画%' ORDER BY age DESC
        QueryWrapper<UserInfoEntity> queryWrapper3 = new QueryWrapper<>();
        queryWrapper3.lambda().like(UserInfoEntity::getSkill,"画");
        queryWrapper3.lambda().orderByDesc(UserInfoEntity::getAge);
        List<UserInfoEntity> userInfoEntityList3 = userInfoService.list(queryWrapper3);
        result.put("studentAgeSkill",userInfoEntityList3);
        //模糊查询名字带有"小"或者年龄大于18的学生
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE name LIKE '%小%' OR age > 18
        QueryWrapper<UserInfoEntity> queryWrapper4 = new QueryWrapper<>();
        queryWrapper4.lambda().like(UserInfoEntity::getName,"小");
        queryWrapper4.lambda().or().gt(UserInfoEntity::getAge,18);
        List<UserInfoEntity> userInfoEntityList4 = userInfoService.list(queryWrapper4);
        result.put("studentOr",userInfoEntityList4);
        //查询评价不为null的学生,并且分页
        //等价SQL: SELECT id,name,age,skill,evaluate,fraction FROM user_info WHERE evaluate IS NOT NULL LIMIT 0,5
        IPage<UserInfoEntity> page = new Page<>();
        page.setCurrent(1);
        page.setSize(5);
        QueryWrapper<UserInfoEntity> queryWrapper5 = new QueryWrapper<>();
        queryWrapper5.lambda().isNotNull(UserInfoEntity::getEvaluate);
        page = userInfoService.page(page,queryWrapper5);
        result.put("studentPage",page);
        return result;
    }
}