MyBatis-Plus全方位通关指南：从零基础到高效开发实战

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.5.12</version>
</dependency>

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-spring-boot3-starter</artifactId><version>3.5.12</version>
</dependency>

@SpringBootTest
class UserMapperTest {@Autowiredprivate UserMapper userMapper;@Testvoid testInsert() {User user = new User();user.setId(5L);user.setUsername("Lucy");user.setPassword("123");user.setPhone("18688990011");user.setBalance(200);user.setInfo("{\"age\": 24, \"intro\": \"英文老师\", \"gender\": \"female\"}");user.setCreateTime(LocalDateTime.now());user.setUpdateTime(LocalDateTime.now());userMapper.insert(user);}@Testvoid testSelectById() {User user = userMapper.selectById(5L);System.out.println("user = " + user);}@Testvoid testQueryByIds() {List<User> users = userMapper.selectByIds(List.of(1L, 2L, 3L, 4L));users.forEach(System.out::println);}@Testvoid testUpdateById() {User user = new User();user.setId(5L);user.setBalance(20000);userMapper.updateById(user);}@Testvoid testDeleteUser() {userMapper.deleteById(5L);}
}

@TableName("user")
public class User {private Long id;private String name;
}

@TableName("user")
public class User {@TableIdprivate Long id;private String name;
}

@TableName("user")
public class User {@TableIdprivate Long id;private String name;private Integer age;@TableField(is_married")private Boolean isMarried;@TableField("`concat`")private String concat;
}

mybatis-plus:type-aliases-package: com.itheima.mp.domain.po      # 别名扫描包mapper-locations: classpath*:/mapper/**/*.xml       # 文件地址 默认值configuration:                                      # 配置map-underscore-to-camel-case: true                # 是否开启下划线和驼峰的映射cache-enabled: false                              # 是否开启二级缓存global-config:                                      #  全局配置db-config:                                      # 数据库配置id-type: assign_id                            # id生成策略update-strategy: not_null                     # 更新策略：只更新非空字段

@Test
void testLambdaQueryWrapper() {// 1.构建条件 WHERE username LIKE "%o%" AND balance >= 1000QueryWrapper<User> wrapper = new QueryWrapper<>();wrapper.lambda().select(User::getId, User::getUsername, User::getInfo, User::getBalance).like(User::getUsername, "o").ge(User::getBalance, 1000);// 2.查询List<User> users = userMapper.selectList(wrapper);users.forEach(System.out::println);
}

@Test
void testCustomWrapper() {// 1.准备自定义查询条件List<Long> ids = List.of(1L, 2L, 4L);QueryWrapper<User> wrapper = new QueryWrapper<User>().in("id", ids);// 2.调用mapper的自定义方法，直接传递WrapperuserMapper.deductBalanceByIds(200, wrapper);
}

package com.itheima.mp.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itheima.mp.domain.po.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Update;
import org.apache.ibatis.annotations.Param;public interface UserMapper extends BaseMapper<User> {@Select("UPDATE user SET balance = balance - #{money} ${ew.customSqlSegment}")void deductBalanceByIds(@Param("money") int money, @Param("ew") QueryWrapper<User> wrapper);
}

package com.itheima.mp.service;import com.baomidou.mybatisplus.extension.service.IService;
import com.itheima.mp.domain.po.User;public interface IUserService extends IService<User> {// 拓展自定义方法
}

package com.itheima.mp.service.impl;import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.itheima.mp.domain.po.User;
import com.itheima.mp.domain.po.service.IUserService;
import com.itheima.mp.mapper.UserMapper;
import org.springframework.stereotype.Service;@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User>implements IUserService {
}

mybatis-plus:global-config:db-config:logic-delete-field: deleted # 全局逻辑删除的实体字段名(since 3.3.0,配置后可以忽略不配置步骤2)logic-delete-value: 1 # 逻辑已删除值(默认为 1)logic-not-delete-value: 0 # 逻辑未删除值(默认为 0)

@Getter
public enum UserStatus {NORMAL(1, "正常"),FREEZE(2, "冻结"),;@EnumValueprivate final int value;@JsonValueprivate final String desc;UserStatus(int value, String desc) {this.value = value;this.desc = desc;}
}

mybatis-plus:configuration:default-enum-type-handler: com.baomidou.mybatisplus.core.handlers.MybatisEnumTypeHandler

<!-- jdk 11+ 引入可选模块 --><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-jsqlparser</artifactId><version>3.5.9</version></dependency><!-- jdk 8+ 引入可选模块 --><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-jsqlparser-4.9</artifactId></dependency>

@Configuration
public class MyBatisConfig {public MybatisPlusInterceptor mybatisPlusInterceptor(){MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));return interceptor;}
}

@Testvoid testPageQuery(){Page<User> p = userService.page(new Page<>(1, 2));System.out.println("p.getTotal() = " + p.getTotal());System.out.println("p.getPages() = " + p.getPages());List<User> records = p.getRecords();records.forEach(System.out::println);}

package com.itheima.mp.domain.query;import com.baomidou.mybatisplus.core.metadata.OrderItem;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import lombok.Data;@Data
public class PageQuery {private Integer pageNo;private Integer pageSize;private String sortBy;private Boolean isAsc;public <T>  Page<T> toMpPage(OrderItem ... orders){// 1.分页条件Page<T> p = Page.of(pageNo, pageSize);// 2.排序条件// 2.1.先看前端有没有传排序字段if (sortBy != null) {p.addOrder(new OrderItem(sortBy, isAsc));return p;}// 2.2.再看有没有手动指定排序字段if(orders != null){p.addOrder(orders);}return p;}public <T> Page<T> toMpPage(String defaultSortBy, boolean isAsc){return this.toMpPage(new OrderItem(defaultSortBy, isAsc));}public <T> Page<T> toMpPageDefaultSortByCreateTimeDesc() {return toMpPage("create_time", false);}public <T> Page<T> toMpPageDefaultSortByUpdateTimeDesc() {return toMpPage("update_time", false);}
}

// 1.构建条件
Page<User> page = query.toMpPageDefaultSortByCreateTimeDesc();

package com.itheima.mp.domain.dto;import cn.hutool.core.bean.BeanUtil;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;import java.util.Collections;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;@Data
@NoArgsConstructor
@AllArgsConstructor
public class PageDTO<V> {private Long total;private Long pages;private List<V> list;/*** 返回空分页结果* @param p MybatisPlus的分页结果* @param <V> 目标VO类型* @param <P> 原始PO类型* @return VO的分页对象*/public static <V, P> PageDTO<V> empty(Page<P> p){return new PageDTO<>(p.getTotal(), p.getPages(), Collections.emptyList());}/*** 将MybatisPlus分页结果转为 VO分页结果* @param p MybatisPlus的分页结果* @param voClass 目标VO类型的字节码* @param <V> 目标VO类型* @param <P> 原始PO类型* @return VO的分页对象*/public static <V, P> PageDTO<V> of(Page<P> p, Class<V> voClass) {// 1.非空校验List<P> records = p.getRecords();if (records == null || records.size() <= 0) {// 无数据，返回空结果return empty(p);}// 2.数据转换List<V> vos = BeanUtil.copyToList(records, voClass);// 3.封装返回return new PageDTO<>(p.getTotal(), p.getPages(), vos);}/*** 将MybatisPlus分页结果转为 VO分页结果，允许用户自定义PO到VO的转换方式* @param p MybatisPlus的分页结果* @param convertor PO到VO的转换函数* @param <V> 目标VO类型* @param <P> 原始PO类型* @return VO的分页对象*/public static <V, P> PageDTO<V> of(Page<P> p, Function<P, V> convertor) {// 1.非空校验List<P> records = p.getRecords();if (records == null || records.size() <= 0) {// 无数据，返回空结果return empty(p);}// 2.数据转换List<V> vos = records.stream().map(convertor).collect(Collectors.toList());// 3.封装返回return new PageDTO<>(p.getTotal(), p.getPages(), vos);}
}

@Override
public PageDTO<UserVO> queryUserByPage(PageQuery query) {// 1.构建条件Page<User> page = query.toMpPageDefaultSortByCreateTimeDesc();// 2.查询page(page);// 3.封装返回return PageDTO.of(page, UserVO.class);
}

@Override
public PageDTO<UserVO> queryUserByPage(PageQuery query) {// 1.构建条件Page<User> page = query.toMpPageDefaultSortByCreateTimeDesc();// 2.查询page(page);// 3.封装返回return PageDTO.of(page, user -> {// 拷贝属性到VOUserVO vo = BeanUtil.copyProperties(user, UserVO.class);// 用户名脱敏String username = vo.getUsername();vo.setUsername(username.substring(0, username.length() - 2) + "**");return vo;});
}