Java @PreUpdate 不适用于 Spring Data JPA
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@PreUpdate does not work with Spring Data JPA
提问by fracz
I have an entity:
我有一个实体：
@Entity
@EntityListeners(MyEntityListener.class)
class MyEntity{ ... }
And the listener:
和听众：
class MyEntityListener{
@PrePersist
@PreUpdate
public void doSomething(Object entity){ ... }
}
I'm using the Spring Data generated DAO for this entity (1.4.1) and EclipseLink. The code behavior is as follows:
我正在为此实体 (1.4.1) 和 EclipseLink 使用 Spring Data 生成的 DAO。代码行为如下：
MyEntity entity = new Entity();
entity = dao.save(entity); // the doSomething() is called here
// change something it the entity and save it again
dao.save(entity); // the doSomething() is NOT called here, checked with breakpoint
The problem has already been described by someone in 2009, however, they did not came up with any solution. I wonder if anyone has and idea how to solve it?
采纳答案by Andrei I
As you said, the callback method is calledthe second time, if the entity is detached or fetched again from DB.
如您所说，如果实体从数据库中分离或再次获取，则第二次调用回调方法。
I cannot explain it exactly, but can think of the scenario described here, when no dirty fields are identified before the second save()call and thus the @PreUpdate callback not called. Or it may be simply a bug within your version of EclipseLink.
我无法准确解释它，但可以想到这里描述的场景，当在第二次save()调用之前没有识别出脏字段，因此没有调用 @PreUpdate 回调。或者它可能只是您的 EclipseLink 版本中的一个错误。
UPDATE
更新
In the JPA 2.0 specification I found the following, which is exactly your behaviour (3.5.2 Semantics of the Life Cycle Callback Methods for Entities):
在 JPA 2.0 规范中，我发现了以下内容，这正是您的行为（3.5.2 实体生命周期回调方法的语义）：
Note that it is implementation-dependent as to whether PreUpdate and PostUpdate call- backs occur when an entity is persisted and subsequently modified in a single transaction or when an entity is modified and subsequently removed within a single transaction. Portable applications should not rely on such behavior.
请注意，当实体在单个事务中被持久化并随后被修改时，或者当实体被修改并随后在单个事务中被删除时，是否发生 PreUpdate 和 PostUpdate 回调取决于实现。便携式应用程序不应依赖此类行为。
回答by Terry Zhao
what is your transactional setting around your two different save()?
您围绕两个不同的 save() 的交易设置是什么？
I think there would be some differnce between save()/update()/merge()/persist(), for the different status of an entity(transient, persistent, detached), the operations is not the same as you thought and your annotation @PrePersist and @PreUpdate did not take effect.
我认为 save()/update()/merge()/persist() 之间会有一些区别，对于实体的不同状态（transient、persistent、detached），操作和你想的不一样，你的注解@PrePersist 和@PreUpdate 没有生效。
