Prevent Cyclic references when converting with MapStruct

Issue

Today I started using MapStruct to create my Model to DTO converters for my project and i was wondering if it handled cyclic references automatically but it turned out it doesn't.

This is the converter i made to test it:

package it.cdc.snp.services.rest.giudizio;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
import org.mapstruct.factory.Mappers;
import org.springframework.stereotype.Component;

import it.cdc.snp.dto.entita.Avvisinotifica;
import it.cdc.snp.dto.entita.Corrispondenza;
import it.cdc.snp.model.notifica.AvvisoDiNotificaModel;
import it.cdc.snp.model.notifica.NotificaModel;
import it.cdc.snp.model.procedimento.ProcedimentoModel;

@Component
@Mapper(componentModel="spring")
public interface NotificaMapper {

    NotificaMapper INSTANCE = Mappers.getMapper( NotificaMapper.class );

    @Mappings({
        @Mapping(source = "avvisinotificas", target = "avvisinotificas"),
    })
    NotificaModel<ProcedimentoModel> corrispondenzaToNotificaModel(Corrispondenza notifica);

    @Mappings({
        @Mapping(source = "corrispondenza", target = "notifica"),
    })
    AvvisoDiNotificaModel avvisinotificaToAvvisoDiNotificaModel(Avvisinotifica avvisinotifica);


}

This is the test:

        Notifica sourceObject1 = new Notifica();
        sourceObject1.setId(new Long(1));
        Avvisinotifica sourceObject2 = new Avvisinotifica();
        sourceObject2.setId(new Long(11));
        List<Avvisinotifica> tests= new ArrayList<>();
        tests.add(sourceObject2);
        sourceObject1.setAvvisinotificas(tests);
        sourceObject2.setCorrispondenza(sourceObject1);

        NotificaModel destObject1 = new NotificaModel<>();
        Avvisinotifica destObject2 = new Avvisinotifica();

        NotificaModel converted = mapper.corrispondenzaToNotificaModel(sourceObject1);

Notifica, Avvisinotifica and their respective models are simple POJOs with setters and getters so i don't think it's needed to post the code (Notifica extends Corrispondenza, if you were wondering)

this code gets into an infinite cycle, nothing very surprising here (though i hoped it'd handle these situations). And while i think i can find an elegant way to manually handle it (i was thinking about using methods with @MappingTarget to insert the Referenced objects ) what i was wondering is if there's some way to tell MapStruct how to automatically handle cyclic references.

Solution

There is no detection or special handling of cases like this in MapStruct yet, but there is a feature request for it: #469. If you got any ideas how to deal with cycles, please drop a comment at that issue.

Answered By - Gunnar