MapStruct是什么

MapStruct是一个代码生成器，用于简化Java实体类型之间转换，使用时只需定义Mapper映射接口，会自动为我们生成转换代码。本质上MapStruct是通过普通方法调用进行字段映射，快速、类型安全、简单、易于理解。

主页： https://mapstruct.org/

GitHub: https://github.com/mapstruct/mapstruct/

Demo: https://github.com/mapstruct/mapstruct-examples

MapStruct使用方式

1.1 Maven坐标

<properties><org.mapstruct.version>1.5.5.Final</org.mapstruct.version>
</properties><dependencies><dependency><groupId>org.mapstruct</groupId><artifactId>mapstruct</artifactId><version>${org.mapstruct.version}</version></dependency>
</dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.8.1</version><configuration><source>1.8</source><target>1.8</target><annotationProcessorPaths><path><groupId>org.mapstruct</groupId><artifactId>mapstruct-processor</artifactId><version>${org.mapstruct.version}</version></path></annotationProcessorPaths></configuration></plugin></plugins>
</build>

1.2 定义基础转换类

package com.giser.mp.entmp;import java.util.List;/**
*
* 基础转换类，提供几个基本方法，直接继承使用
* 更多的用法需自行实现
* @param <DTO> 目标对象，一般为DTO对象
* @param <ENTITY> 源对象，一般为需要转换的对象
* @param <VO> 目标对象，一般为VO对象
*/
public interface BaseMapStructMapper<DTO, ENTITY, VO> {/*** 将源对象转换为DTO对象* @param e* @return D*/DTO entityToDTO(ENTITY e);/*** 将源对象集合转换为DTO对象集合* @param es* @return List<D>*/List<DTO> entitiesToDTOList(List<ENTITY> es);/*** 将源对象转换为VO对象* @param e* @return V*/VO entityToVO(ENTITY e);/*** 将DTO对象转换为VO对象* @param d* @return V*/VO dtoToVO(DTO d);/*** 将源对象集合转换为VO对象集合* @param es* @return List<D>*/List<VO> entitiesToVOList(List<ENTITY> es);/*** 将目标对象转换为源对象* @param d* @return E*/ENTITY dtoToEntity(DTO d);/*** 将目标对象集合转换为源对象集合* @param ds* @return List<E>*/List<ENTITY> dtosToEntityList(List<DTO> ds);}

13 使用时，继承基础转换类，并标注@Mapper注解(org.mapstruct.Mapper)即可

@Mapper(componentModel = "spring")
public interface EarlyEntityMapper extends BaseMapStructMapper<EarlyDto, EarlyEntity, EarlyVo> {
}

1.4 测试

/*** @see https://mapstruct.org/* @see https://github.com/mapstruct/mapstruct/* @see https://github.com/mapstruct/mapstruct-examples*/
@SpringBootTest(classes = JavaMpApp.class)
@Slf4j
public class MapStructTest {@Autowiredprivate EarlyEntityMapper earlyEntityMapper;@Testpublic void testDto2Ent(){EarlyDto earlyDto = new EarlyDto(1L,"xiangjiao dto",22,null);EarlyEntity entity = earlyEntityMapper.dtoToEntity(earlyDto);System.out.println(entity);}
}

5.编译后的文件

package BOOT-INF.classes.com.giser.mp.entmp;import com.giser.mp.entity.EarlyDto;
import com.giser.mp.entity.EarlyEntity;
import com.giser.mp.entity.EarlyVo;
import com.giser.mp.entmp.EarlyEntityMapper;
import java.util.ArrayList;
import java.util.List;
import org.springframework.stereotype.Component;@Component
public class EarlyEntityMapperImpl implements EarlyEntityMapper {public EarlyDto entityToDTO(EarlyEntity e) {if (e == null)return null; EarlyDto earlyDto = new EarlyDto();earlyDto.setId(e.getId());earlyDto.setName(e.getName());earlyDto.setAge(e.getAge());earlyDto.setEmail(e.getEmail());return earlyDto;}public List<EarlyDto> entitiesToDTOList(List<EarlyEntity> es) {if (es == null)return null; List<EarlyDto> list = new ArrayList<>(es.size());for (EarlyEntity earlyEntity : es)list.add(entityToDTO(earlyEntity)); return list;}public EarlyVo entityToVO(EarlyEntity e) {if (e == null)return null; EarlyVo earlyVo = new EarlyVo();earlyVo.setId(e.getId());earlyVo.setName(e.getName());earlyVo.setAge(e.getAge());earlyVo.setEmail(e.getEmail());return earlyVo;}public EarlyVo dtoToVO(EarlyDto d) {if (d == null)return null; EarlyVo earlyVo = new EarlyVo();earlyVo.setId(d.getId());earlyVo.setName(d.getName());earlyVo.setAge(d.getAge());earlyVo.setEmail(d.getEmail());return earlyVo;}public List<EarlyVo> entitiesToVOList(List<EarlyEntity> es) {if (es == null)return null; List<EarlyVo> list = new ArrayList<>(es.size());for (EarlyEntity earlyEntity : es)list.add(entityToVO(earlyEntity)); return list;}public EarlyEntity dtoToEntity(EarlyDto d) {if (d == null)return null; EarlyEntity earlyEntity = new EarlyEntity();earlyEntity.setId(d.getId());earlyEntity.setName(d.getName());earlyEntity.setAge(d.getAge());earlyEntity.setEmail(d.getEmail());return earlyEntity;}public List<EarlyEntity> dtosToEntityList(List<EarlyDto> ds) {if (ds == null)return null; List<EarlyEntity> list = new ArrayList<>(ds.size());for (EarlyDto earlyDto : ds)list.add(dtoToEntity(earlyDto)); return list;}
}