Hibernate JPA Entity侦听器@Pre和@Post无法按预期工作 [英] Hibernate JPA Entity listener @Pre and @Post don't work as expected

问题描述

我正在构建一个实时应用程序，并尝试使用实体监听器来保持我的状态为最新状态。基本思想是，无论何时某个业务逻辑领域发生变化，我都会重新加载受影响的实体并协调这些变更。这是一个MWE：

I'm building a real time app and trying to use entity listeners to keep my state up to date. The basic idea is that whenever an area of business logic changes, I re-load the affected entities and reconcile the changes. Here's a MWE:

@PrePersist
public void PrePersist() {
    LoggerFactory.logger(App.class).info(" >>> PrePersist count: " + getStars().size());
}
@PostPersist
public void PostPersist() {
    LoggerFactory.logger(App.class).info(" >>> PostPersist count: " + getStars().size());
}
@PreRemove
public void PreRemove() {
    LoggerFactory.logger(App.class).info(" >>> PreRemove count: " + getStars().size());
}

@PostRemove
public void PostRemove() {
    LoggerFactory.logger(App.class).info(" >>> PostRemove count: " + getStars().size());
}
private List<Star> getStars() {
    EntityManager em = HibernateUtilJpa.getEntityManager();
    List<Star> l = new ArrayList<Star>();
    try {
        em.getTransaction().begin();
        l = em.createQuery("from Star", Star.class).getResultList();
        em.getTransaction().commit();
    } catch (Exception e) {
        em.getTransaction().rollback();
    } finally {
        em.close();
    }
    return l;
}

我正在使用一个单独的API向数据库中插入/删除星星。我期待后继者会因为添加的项目而显示更多项目，并且删除后的项目数量会少于预先移除的项目数量。事实并非如此，后续持久化和移除后都显示不正确的项目数，因此预留持久性与持久性持久性相同，并且预先移除与移除后相同。我确信它与Hibernate-s缓存有关，但我使用的是事务，一切都通过 EntityManager ，所以我在挠头。

I'm using a separate API to insert/remove stars into DB. I was expecting that post-persist would show one item more because of the added item, and post-remove would be one fewer than pre-remove. This is not the case, both post-persist and post-remove show the incorrect number of items, so pre-persist is the same as post-persist, and pre-remove is the same as post-remove. I'm sure it has to do with Hibernate-s caching, but I'm using transactions and everything goes through the EntityManager so I'm scratching my head.

推荐答案

从 documentation ：
$ b

From the documentation:

回调方法不能调用 EntityManager 或 Query methods！

A callback method must not invoke EntityManager or Query methods!

在实践中，如果你这样做的行为是未定义的，那么你在例子中观察到的结果。

In practice, the behaviour if you do it is undefined, hence the results you observe in your examples.

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