Hibernate集合在persist后为空

Question

JPA实体batch与event具有OneTomany关系：

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

和事件与批处理有多个关系：

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

在创建新实例并持久化它之后，ContainingEvents仍然是Null。但当我使用空的set:

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

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批注中添加CascadeType，例如：

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

而event类必须包含：

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