使用连接表在多对多关系中进行 JPQL 查询

Question

下面是三个实体。我想使用 JPA

通过 DEP id 获取规则列表

规则------------一对多------------>EMP------------多对多-------- ---->部门

 @Entity
    @Table(name = "EMP")
    public class Emp implements Serializable {
        private static final long serialVersionUID = 1L;

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;


        @OneToMany(mappedBy = "emp")
        private List<Rule> rules;

        @ManyToMany
        @JoinTable(name = "rule_ref_sub_category_ref", joinColumns = {
                @JoinColumn(name = "EMP_ID") }, inverseJoinColumns = { @JoinColumn(name = "DEP_REF_ID") })
        private List<Dep> Deps;
    }


     */
    @Entity
    @Table(name="DEP")
    public class Dep implements Serializable {
        private static final long serialVersionUID = 1L;

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

        @Column(name="LABEL")
        private String label;

        private int mandatory;

        @ManyToMany(mappedBy="Deps")
        private List<Emp> emps;

    }

    @Entity
    @Table(name="RULES")
    public class Rule implements Serializable {
        private static final long serialVersionUID = 1L;

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


        @ManyToOne
        @JoinColumn(name="EMP_REF_ID")
        private Emp emp;
    }

有人可以通过示例 JPQL 请求来指导我解决这个问题吗？

Answer 1

这是一个非常简单的查询

select r from rule r
join r.emp emp
join emp.Deps dep
where dep.id = :depId

阅读一点 docs 以了解连接语法的可能形式

使用连接表在多对多关系中进行 JPQL 查询

JPQL Quesry in ManyToMany relation using JoinTable

hibernate

jpa

jpql