java - Hibernate集合在持久化后为NULL

Question

JPA 实体 Batch 与 Event 具有 OneToMany 关系:

@OneToMany(mappedBy = "owningBatch")
private Set<Event> containingEvents;

和Event与Batch有ManyToOne关系:

@ManyToOne
@JoinColumn(name = "BATCH_ID")
private Batch owningBatch;

创建新实例并将其保留后，containingEvents 仍为 NULL。 但是当我使用空 Set 时:

@OneToMany(mappedBy = "owningBatch")
private Set<Event> containingEvents = Sets.newHashSet();

然后在持久化之后，containingEvents 被替换为 Hibernate 的 PersistentSet。 我希望即使在第一种情况下也会发生这种替换。为什么没有发生？

DAO 由 Spring Data JPA 实现。

Spring Boot 2.0.4.RELEASE
Spring Data JPA 2.0.4.RELEASE
Hibernate 5.2.17.Final
Hibernate JPA 2.1 1.0.2.Final

Answer 1

您需要在@OneToMany注释中添加CascadeType，例如:

@OneToMany(mappedBy = "owningBatch", cascade = CascadeType.ALL)
private Set<Event> containingEvents;

并且您的 Event 类必须包含:

@ManyToOne
@JoinColumn(name = "batch_id", referencedColumnName = "id")
private Batch owningBatch;