我有以下实体:
@Entity
@Getter @Setter @NoArgsConstructor @RequiredArgsConstructor
public class Link extends Auditable {
@Id
@GeneratedValue
private Long id;
@NonNull
private String title;
@NonNull
private String url;
@OneToMany(cascade = CascadeType.ALL, mappedBy = "link")
private List<Comment> comments = new ArrayList<>();
@Transient
@Setter(AccessLevel.NONE)
private String userAlias ;
public String getUserAlias() {
if(user == null)
return "";
return user.getAlias();
}
@ManyToOne
private User user;
public Long getUser() {
if(user == null)
return -1L;
return user.getId();
}
public void addComment(Comment c) {
comments.add(c);
c.setLink(this);
}
}
@Entity
@Getter @Setter @NoArgsConstructor @RequiredArgsConstructor
public class Comment extends Auditable{
@Id
@GeneratedValue
private Long id;
@NonNull
private String comment;
@ManyToOne(fetch = FetchType.LAZY)
private Link link;
public Long getLink() {
return link.getId();
}
}
如果我创建评论和链接,请将链接与评论相关联,然后保存即可。
例如:
Link link = new Link("Getting started", "url");
Comment c = new Comment("Hello!");
link.addComment(c);
linkRepository.save(link);
但是,如果我先保存评论:
Link link = new Link("Getting started", "url");
Comment c = new Comment("Hello!");
commentRepository.save(c);
link.addComment(c);
linkRepository.save(link);
我明白
Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on uk.me.dariosdesk.dariodemo.domain.Comment.link references an unknown entity: uk.me.dariosdesk.dariodemo.domain.Link
at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:97) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processEndOfQueue(InFlightMetadataCollectorImpl.java:1815) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processFkSecondPassesInOrder(InFlightMetadataCollectorImpl.java:1759) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1646) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:287) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:903) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:934) ~[hibernate-core-5.4.0.Final.jar:5.4.0.Final]
将级联类型从 ALL 更改为 MERGE 似乎可以解决问题并接受这两种实现。 (即:添加预先存在的评论或创建两者,然后通过链接保存)
1)这是为什么? 2) 使用 MERGE 而不是 ALL 时有什么需要注意的吗?
最佳答案
存储库保存方法检查实体是否存在。对于新实体,调用持久化,对于持久化实体,调用合并。
@Transactional
public <S extends T> S save(S entity) {
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity);
}
}
在第二个用例中,链接是新实体,因此调用 persist() 。使用 CascadeType.ALL persist() 级联到 Comment 实体。注释已经持久化,需要合并,persist() 失败。
如果使用 CascadeType.MERGE persist() 不会级联到 Comment。它不会失败。
关于spring-boot - SpringBoot CascadeType ALL 与 MERGE 和分离实体,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55210341/