DTO toDto(E entity);

    @Condition
    default boolean isEntityAvailable(E entity) {
        if (entity == null) {
            return false;
        }
        return Persistence.getPersistenceUtil().isLoaded(entity);
    }

    @Override
    public SubCategoryDto toDto(SubCategory entity) {
        if ( entity == null ) {
            return null;
        }
        if ( !isEntityAvailable( entity ) ) {
            return null;
        }
        SubCategoryDto.SubCategoryDtoBuilder<?, ?> subCategoryDto = SubCategoryDto.builder();
        subCategoryDto.id( entity.getId() );
        subCategoryDto.name( entity.getName() );
        subCategoryDto.nick( entity.getNick() );
        return SubCategoryDto.build();
    }

    @Override
    public SubCategoryDto toDto(SubCategory entity) {
        if ( entity == null ) {
            return null;
        }
        SubCategoryDto.SubCategoryDtoBuilder<?, ?> subCategoryDto = SubCategoryDto.builder();
        subCategoryDto.id( entity.getId() );
        subCategoryDto.name( entity.getName() );
        subCategoryDto.nick( entity.getNick() );
        return SubCategoryDto.build();
    }

    @Override
    public SubCategoryDto toDto(SubCategory entity) {
        if ( entity == null ) {
            return null;
        }
        SubCategoryDto.SubCategoryDtoBuilder<?, ?> subCategoryDto = SubCategoryDto.builder();

        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.id( entity.getId() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.name( entity.getName() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.nick( entity.getNick() );
        }

        return SubCategoryDto.build();
    }

public interface EntityMapper<DTO extends EntityDto, E extends BasicEntity> {
    E toEntity(DTO dto);

    DTO toDto(E entity);

    // try to avoid JPA lazy loading issue
    // and this one worked well
    @Condition
    default boolean isCollectionAvailable(Collection<E> collection) {
        if (collection == null) {
            return false;
        }
        return Persistence.getPersistenceUtil().isLoaded(collection);
    }

    // try to avoid JPA lazy loading issue
    // got problem with this
    @Condition
    default boolean isEntityAvailable(E entity) {
        if (entity == null) {
            return false;
        }
        return Persistence.getPersistenceUtil().isLoaded(entity);
    }

    @MapperConfig(mappingControl = DeepClone.class,
                  mappingInheritanceStrategy = MappingInheritanceStrategy.AUTO_INHERIT_ALL_FROM_CONFIG)
    interface Config {
    }
}

@Mapper(config = EntityMapper.Config.class, uses = {SubCategoryMapper.class})
public interface ParentCategoryMapper extends EntityMapper<ParentCategoryDto, ParentCategory> {
}

@Mapper(config = EntityMapper.Config.class, uses = {ParentCategoryMapper.class})
public interface SubCategoryMapper extends EntityMapper<SubCategoryDto, SubCategory> {
}

    @Override
    public SubCategoryDto toDto(SubCategory entity) {
        if ( entity == null ) {
            return null;
        }
        SubCategoryDto.SubCategoryDtoBuilder<?, ?> subCategoryDto = SubCategoryDto.builder();
        // Calling isEntityAvailable() so much times does not make any sense.
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.id( entity.getId() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.name( entity.getName() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.nick( entity.getNick() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.theOrder( entity.getTheOrder() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.icon( entity.getIcon() );
        }
        if ( isEntityAvailable( entity ) ) {
            subCategoryDto.link( entity.getLink() );
        }
        // this is right
        if ( ParentCategoryMapper.isEntityAvailable( entity.getParentCategory() ) ) {
            subCategoryDto.parentCategory( ParentCategoryMapper.toDto( entity.getParentCategory() ) );
        }
        return SubCategoryDto.build();
    }

    @Override
    public SubCategoryDto toDto(SubCategory entity) {
        if ( entity == null ) {
            return null;
        }
        if ( !isEntityAvailable( entity ) ) {
            return null;
        }
        SubCategoryDto.SubCategoryDtoBuilder<?, ?> subCategoryDto = SubCategoryDto.builder();
        subCategoryDto.id( entity.getId() );
        subCategoryDto.name( entity.getName() );
        subCategoryDto.nick( entity.getNick() );
        subCategoryDto.theOrder( entity.getTheOrder() );
        subCategoryDto.icon( entity.getIcon() );
        subCategoryDto.link( entity.getLink() );
        if ( ParentCategoryMapper.isEntityAvailable( entity.getParentCategory() ) ) {
            subCategoryDto.parentCategory( ParentCategoryMapper.toDto( entity.getParentCategory() ) );
        }
        return SubCategoryDto.build();
    }