java - JPA OneToMany-Mapping 没有多边映射类

Question

在使用 JPA 2.1 和 Hibernate 的 Spring Boot 应用程序中，有两个感兴趣的 (PostgreSQL) 表:

entity                                external_id--                                    --id serial                             id serial...                                   entity_id int...                                   external_id int

The relation between entity and external_ids is obviously OneToMany, which I want to use in the JPA mapping as well. A simple way to do this is to create @Entity-mappings for each table and use a @OneToMany-relation:

@Entity
public class Entity {
  @Id
  private Integer id;

  @OneToMany(mappedBy= "entityId")
  private Set<ExternalId> externalIds;
}

@Entity
public class ExternalId {
  @Id
  private Integer id;

  @ManyToOne
  private Integer entityId;

  private Integer externalId;
}

但由于表 external_ids 只包含每个实体成员的数字列表，我想在没有表 external_id 的显式映射的情况下立即映射 external_id.external_id 的值:

@Entity
public class Entity {
  @Id
  private Integer id;

  @OneToMany(???)
  private Set<Integer> externalIds;
}

这对于 JPA 2.1 是否可行？如果可行，如何实现？

Answer 1

您可以利用 @ElementCollection为此目的:

@ElementCollection
@CollectionTable(name = "TableName", joinColumns=@JoinColumn(name = "JoinColumnName"))
private Set<Integer> externalIds;