JPA Criteria API Set 是否包含该值？

Question

想象一下图书馆。图书馆有书。每本书都是一个单独的实体。图书馆里有读者（人民）。当一个人拿一本书看的时候，我表示这本书是别人看过的。

问题的主题区已经重新设计，不要发誓逻辑

我不明白如何进行条件查询以查看 Set<People> peoples 是否包含某个人

的人

@Entity
@Table(name = "book")
public class Book{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long id;

    @Column
    @NotEmpty
    String title;

    @ManyToMany(cascade = {
            CascadeType.PERSIST,
            CascadeType.MERGE
    })
    @JoinTable(name = "people_read",
            joinColumns = @JoinColumn(name = "id_people"),
            inverseJoinColumns = @JoinColumn(name = "id_book"))
    Set<People> peoples = new HashSet<>();
}

@Getter
@Setter
@Entity
@Table(name = "people")
public class People {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    Long id;

    @Column
    @NotEmpty
    String name;

    @ManyToMany(mappedBy = "peoples")
    Set<Book> books = new HashSet<>();
}

我想做什么：

Path<Object> peoples = root.get("peoples");
(Predicate) query.where(peoples .get("id").in(cb.parameter(Set.class, "3"))); //3 is for example the id of people whom I want to know if they have read the book

Answer 1

我不知道如何编写仅检查 Id 的查询，但如果您有一个 People 实例，查询将如下所示

query.where(cb.isMember(peopleInstance, root.get("peoples"))

JPA Criteria API Set 是否包含该值？

JPA Criteria API does Set contain the value?

java

jpa

collections

criteria-api