@Entity
@Table(name = "one")
public class One {
  ...  
  @OneToMany(mappedBy = "one")
  private Set<Many> manys = new HashSet<>();  
  ...  
  public void setManys(Set<Many> manys) {
    this.manys = manys;
  }  
  public Set<Many> getManys() {
    return manys;
  }
}

@Entity
@Table(name = "many")
public class Many {
  ...  
  @ManyToOne
  private One one;
}

public class OneDTO {
  ...
  // mark 1
  private Set<ManyDTO> manyDTOS = new HashSet<>();
    ...
   public void setManyDTOS(Set<ManyDTO> manyDTOS) {
    this.manyDTOS = manyDTOS;
  }
  
  public Set<ManyDTO> getManyDTOS() {
    return manyDTOS;
  }
}
  public class ManyDTO {
  ...  
  private Long oneId;  
  ...  
  public void setOneId(Long oneId) {
    this.oneId = oneId;
  }
  
  public Long getOneId() {
    return oneId;
  }
}

// mark 2
@Mapper(componentModel = "spring", uses = {ManyMapper.class})
public interface OneMapper extends EntityMapper<OneDTO, One> {  
  // mark 3
  @Mapping(souce = "manys", target = "manyDTOS")
  OneDTO toDto(One one);
  
  ...
  
}
@mapper(componentModel = "spring", uses = {OneMapper.class})
public interface ManyMapper extends EntityMapper<ManyDTO, Many>{  
  ...  
}