java - JPA 与规范 - 如何通过子集合内容过滤实体？

Question

我面临着通过列表中子项的值过滤实体的问题。 例如:

public class Father(){
  private String name;
  private Set<Child> childs;
}
public class Child(){
  private String name;
  private Integer age;
  private School school;
}
public class School(){
  private String name;
}

我想过滤所有在 X 学校有 child 的父亲。

这就是我所做的，但无法正常工作:

 Specification specs = new Specificatrion(){
        @Override
        public Predicate toPredicate(Root<Father> root, CriteriaQuery<?> query, final CriteriaBuilder cb){
             Root<Child> childRoot = query.from(Child.class);
             Path<?> path = childRoot.get(Child_.school.name);
             Predicate pred = exp.in("School Name");
             return cb.and(pred);
         }
}

有人可以帮我解决这个问题吗？ 谢谢!

Answer 1

您必须在 child 与父亲之间建立反向关系，以便 child 可以在学校和父亲之间架起桥梁。

这样的事情会起作用:

@Entity
public class Father {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;

    @OneToMany(mappedBy = "father", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private Set<Child> childs = new HashSet<>();


@Entity
public class Child {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String name;
    private Integer age;

    @ManyToOne(cascade=CascadeType.ALL)
    private Father father;

    @OneToOne(cascade = CascadeType.PERSIST)
    private School school;

然后在你的FatherRepository中:

@Query("select father from Child child join child.father father join child.school school where school.name=:school")
List<Father> findBySchool(@Param("school") String school);