添加到集合时，PreUpdate不会触发 [英] PreUpdate not firing when adding to a collection

问题描述

  @Entity 
 public class Employee { 
 @Id 
 private int id; 
 @Basic 
私人字符串名称; 
 @OneToMany 
 @JoinTable（name =ORG，joinColumns = @JoinColumn（name =MINION），
 inverseJoinColumns = @JoinColumn（name =EMP））
私人列表<员工> minions = new ArrayList< Employee>（）; 
 
 @PreUpdate 
 public void preUpdate（）{...} 
} 
  

我所看到的是，如果我有一个托管的Employee实体并添加到它的小爪子集合中，则不会调用 preUpdate 方法。新的行被添加到数据库中的映射表中，所以我知道更新正在进行。如果我直接在员工上更改属性，如名称，那么在事务提交时按预期触发 preUpdate 。

<有没有一种方法可以在映射集合被修改时获取PreUpdate？或者是否有其他技术或Hibernate特定的注释来检测这种情况何时发生？

解决方案

@PreUpdate 事件在数据库UPDATE操作是针对有问题的实体执行的。

如果您未更新 Employee ，没有 UPDATE 来执行它的表，因此从不调用 @PreUpdate 侦听器。您应该使用 @PrePersist 事件来获得更好的运气，这是由flush而不是update触发的。

I have a JPA annotated class which contains a collection like so:

@Entity
public class Employee {
    @Id
    private int id; 
    @Basic
    private String name;    
    @OneToMany
    @JoinTable(name = "ORG", joinColumns = @JoinColumn(name="MINION"),
        inverseJoinColumns = @JoinColumn(name="EMP"))
    private List<Employee> minions = new ArrayList<Employee>();

    @PreUpdate
    public void preUpdate(){ ... }
}

What I'm seeing is that if I have a managed Employee entity and I add to it's collection of minions the preUpdate method is not getting invoked. A new row is added to the mapping table in the DB so I know the update is going through. If I change a property directly on the Employee, like name, then preUpdate fires as expected when the transaction is committed.

Is there a way to get PreUpdate to fire when a mapped collection is modified? Or is there some other technique or Hibernate specific annotation for detecting when this happens?

解决方案

@PreUpdate event is triggered just before database UPDATE operation is executed for the entity in question.

If you're not updating direct properties of Employee, there's no UPDATE to execute for its table and thus @PreUpdate listener is never called. You should have better luck using @PrePersist event which is triggered by "flush" rather than "update".

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