如何建模谓词w/ BooleanBuilder (QueryDSL)一个可选的OnetoOne JPA/Hibernate关系？

import com.querydsl.core.BooleanBuilder;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQueryFactory;

public class Example {
    private final JPAQueryFactory queryFactory;

    public Example(JPAQueryFactory queryFactory) {
        this.queryFactory = queryFactory;
    }

    public Predicate buildPredicate(Boolean hasTargetEntity) {
        QSourceEntity sourceEntity = QSourceEntity.sourceEntity;
        BooleanBuilder builder = new BooleanBuilder();

        if (hasTargetEntity) {
            builder.and(sourceEntity.targetEntity.isNotNull());
        } else {
            builder.and(sourceEntity.targetEntity.isNull());
        }

        return builder;
    }

    public void queryEntities(Boolean hasTargetEntity) {
        QSourceEntity sourceEntity = QSourceEntity.sourceEntity;
        Predicate predicate = buildPredicate(hasTargetEntity);

        queryFactory.selectFrom(sourceEntity)
                .where(predicate)
                .fetch();
    }
}