自动休眠保存关系

Question

Basically my question is why if I have an Hibernate relationship like this one.

  @OneToMany(cascade = {CascadeType.ALL})
@JoinColumn(name = "candidacy_id", nullable = false)
@XmlElement
@JsonIgnore
@Getter
@Setter
private List<EvaluationSelectionCriteria> evaluationSelectionCriterias = new ArrayList<>();

   @ManyToOne
   @JoinColumn(name = "candidacy_id", nullable = false, insertable = false, updatable = false)
   @XmlTransient
  @Getter
  @Setter
   private Candidacy candidacy;

Why if I do this candidacy.setEvaluationSelectionCriteria(list) automatically this list is persisted in database?

I would like to use the EvaluationSelectionCriteria as a repository to render a list of "future" EvaluationSelectionCriteria

Could be because is not Lazy?

More detail explanation

So would be like I call method a, there I´m get from database entity A then I set a list into A and then I return A in the method but I´m not saving A, when I see the value of the list already have ids!!!

Answer 1

If you do not want the list to be saved when the parent entity is saved/merged, you should remove or restrict the cascade setting for the relationship:

@OneToMany
private List<EvaluationSelectionCriteria> evaluationSelectionCriterias

or

@OneToMany(cascade = CascadeType.REMOVE) // or other values from the enum
private List<EvaluationSelectionCriteria> evaluationSelectionCriterias

EDIT : If you want to fetch an entity in a transactional method and modify it, you can restrict the scope of the transaction to the fetching only. Then modify the entity outside the transactional method. Later, you can merge the detached entity if needed.

Since collection attributes are lazy per default you will either need to

• access their content while still inside the transactional method - so the collection can be fetched from the DB. Please note that you will have to call a method on the collection that actualy requires it's content to be loaded, like getCriterias().size() .

• use LEFT JOIN FETCH to load the collection as a side effect of the query.

I would not modify the FlushMode for the session - while this would probably work, it feels like a kludge - it does not communicate your intent very well. Explicitly fetching the collection and modifying it outside the transaction expresses your intent better IMO.

Answer 2

我找到了解决方案，忘了说我在使用Spring，所以最后我将@Transactional（readOnly = true）添加到我的方法中，而不是在服务类级别。