mapstruct mapping Entity OneToMany to DTO and reverse

Question

I'm trying to use a mapstruct and I need to mapping Entity with a sub Entity list, I have relationship oneToMany and manyToOne and I need to mapping in both cases:

@Data
@Entity
public class EmailEntity {

private int id;  

... // some fields

@ManyToOne
private DeliveredEmailInfoEntity deliveredEmailInfo;

}

.

@Data
@Entity
public class DeliveredEmailInfoEntity {

private int id;

... // some fields  

@OneToMany
private List<EmailEntity> emails;

}

mapping to:

@Data
public class EmailDTO {

private int id;  

... // some fields

private DeliveredEmailInfoDTO deliveredEmailInfo;

}

.

@Data
public class DeliveredEmailInfoDTO {

private int id;

... // some fields  

private List<EmailDTO> emails;

}

How to do it in the best way ?

Answer 1

To avoid infinite cross setting of nested fields you should limit this dependency, for example on the second nested level, i.e. your root EmailDTO will have one nested DeliveredEmailInfoDTO object (many-to-one relationship), while your root DeliveredEmailInfoDTO will have the list of nested EmailDTO objects (one-to-many relationship) and nothing on the next nesting level:

@Mapper(uses = DeliveredEmailInfoMapper.class)
public interface EmailMapper {

    @Mapping(target = "deliveredEmailInfo.emails", ignore = true)
    EmailDTO toDTO(EmailEntity entity);

    // other methods omitted 

    @Named("emailDTOList")
    default List<EmailDTO> toEmailDTOList(List<EmailEntity> source) {
        return source
                .stream()
                .map(this::toDTO)
                .peek(dto -> dto.setDeliveredEmailInfo(null))
                .collect(Collectors.toList());
    }
}

@Mapper(uses = EmailMapper.class)
public interface DeliveredEmailInfoMapper {

    @Mapping(target = "emails", source = "emails", qualifiedByName = "emailDTOList")
    DeliveredEmailInfoDTO toDTO(DeliveredEmailInfoEntity entity);

    // other methods omitted 

}