使用 CriteriaBuilder 在 Java 中获取列表的 IllegalStateException

总结一下，我有 3 个实体，主要的一个是名为“Rac”的实体。它包含“RacNatureza”列表，其中包含属性“Natureza”。

Rac

    @Entity
    @Table(name = "rac")
    public class Rac {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long idRac;    

    @OneToMany(mappedBy = "rac", cascade = {CascadeType.ALL}, orphanRemoval = true)
    @JsonManagedReference //para evitar recursão infinita do JSON
    private List<RacNatureza> racNaturezas;

    //...getters and setters ok
}

自然奇观

@Entity
@Table(name = "rac_natureza")
public class RacNatureza implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id_rac_natureza")
    private Long idRacNatureza;

    @ManyToOne
    @JsonBackReference //coloquei para evitar a recursao infinita de JSON
    @JoinColumn(name="id_rac")
    private Rac rac;

    @ManyToOne
    @JoinColumn(name="id_natureza")
    private Natureza natureza;

    @Column(name = "principal")
    private Boolean principal;
}

Natureza

@Entity
@Table(name = "natureza")
public class Natureza {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id_natureza")
    private Integer idNatureza;
    private String descricao;

    @OneToMany(mappedBy = "natureza", fetch = FetchType.EAGER, orphanRemoval = true)
    @JsonIgnore
    private List<RacNatureza> racNatureza;
}

我正在尝试使用过滤器开发搜索，在本例中，用户选择“Natureza”列表，然后系统必须显示哪些“Rac”包含用户选择的 Natureza。为此，我尝试使用 Entitymanager 和 Criteriabuilder 来实现。

我尝试编写这样的表达式但不起作用（我没有使用元模型）：

@PersistenceContext
private EntityManager entityManager;

@Override
public List<Rac> filtrar(RacFilter racFilter) {
    CriteriaBuilder builder = entityManager.getCriteriaBuilder();
    CriteriaQuery<Rac> criteria = builder.createQuery(Rac.class);
    Root<Rac> root = criteria.from(Rac.class);

    Predicate[] predicates = criarRestricoes(racFilter, builder, root);
    criteria.where(predicates);

    TypedQuery<Rac> query = entityManager.createQuery(criteria);
    return query.getResultList();

}

@Override
public Predicate[] criarRestricoes(RacFilter racFilter, CriteriaBuilder builder, Root<Rac> root) {
    List<Predicate> predicates = new ArrayList<>();
    if (racFilter.getNaturezas() != null) {
        predicates.add(
                builder.equal(root.<List<RacNatureza>>get("racNaturezas").<Natureza>get("natureza"), racFilter.getNaturezas()) );
    }   
    return predicates.toArray(new Predicate[predicates.size()]);
}

因此，使用上面的代码我收到以下错误：引起原因：java.lang.IllegalStateException：非法尝试取消引用基本类型的路径源 [null.racNaturezas]

我相信错误就在这一行，但我真的不知道如何修复它：

    predicates.add(
            builder.equal(root.<List<RacNatureza>>get("racNaturezas").<Natureza>get("natureza"), racFilter.getNaturezas()) );
}   

Replace root.get("racNaturezas") with root.join("racNaturezas")

请不要问我为什么我们不能使用get