我基于Spring Data jpa的回答是:我只是在外部方法中添加了一个@Transactional注释。

为什么它有效

由于没有活动的Hibernate Session上下文，子实体立即被分离。提供一个Spring (Data JPA)事务可以确保存在Hibernate会话。

参考:

https://vladmihalcea.com/a-beginners-guide-to-jpa-hibernate-entity-state-transitions/

通过在下一个对象之前保存依赖对象来解决。

这发生在我身上，因为我没有设置Id(这不是自动生成的)。并试图拯救@ManytoOne的关系

解决方案很简单，只需使用CascadeType。MERGE而不是CascadeType。PERSIST或CascadeType.ALL。

我也遇到过同样的问题和CascadeType。MERGE对我很有效。

我希望你已经整理好了。

您需要为每个帐户设置事务。

foreach(Account account : accounts){
    account.setTransaction(transactionObj);
}

或者在许多方面将id设置为null就足够了(如果合适的话)。

// list of existing accounts
List<Account> accounts = new ArrayList<>(transactionObj.getAccounts());

foreach(Account account : accounts){
    account.setId(null);
}

transactionObj.setAccounts(accounts);

// just persist transactionObj using EntityManager merge() method.

也许这是OpenJPA的bug，当回滚时它重置了@Version字段，但pcVersionInit保持true。我有一个声明@Version字段的AbstraceEntity。我可以通过重置pcVersionInit字段来解决它。但这不是一个好主意。我认为它不工作时，级联坚持实体。

    private static Field PC_VERSION_INIT = null;
    static {
        try {
            PC_VERSION_INIT = AbstractEntity.class.getDeclaredField("pcVersionInit");
            PC_VERSION_INIT.setAccessible(true);
        } catch (NoSuchFieldException | SecurityException e) {
        }
    }

    public T call(final EntityManager em) {
                if (PC_VERSION_INIT != null && isDetached(entity)) {
                    try {
                        PC_VERSION_INIT.set(entity, false);
                    } catch (IllegalArgumentException | IllegalAccessException e) {
                    }
                }
                em.persist(entity);
                return entity;
            }

            /**
             * @param entity
             * @param detached
             * @return
             */
            private boolean isDetached(final Object entity) {
                if (entity instanceof PersistenceCapable) {
                    PersistenceCapable pc = (PersistenceCapable) entity;
                    if (pc.pcIsDetached() == Boolean.TRUE) {
                        return true;
                    }
                }
                return false;
            }

这是我的药。

Below is my Entity. Mark that the id is annotated with @GeneratedValue(strategy = GenerationType.AUTO), which means that the id would be generated by the Hibernate. Don't set it when entity object is created. As that will be auto generated by the Hibernate. Mind you if the entity id field is not marked with @GeneratedValue then not assigning the id a value manually is also a crime, which will be greeted with IdentifierGenerationException: ids for this class must be manually assigned before calling save()

@Entity
@Data
@NamedQuery(name = "SimpleObject.findAll", query="Select s FROM SimpleObject s")
public class SimpleObject {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String key;

    @Column
    private String value;

}

这是我的主类。

public class SimpleObjectMain {

    public static void main(String[] args) {

        System.out.println("Hello Hello From SimpleObjectMain");

        SimpleObject simpleObject = new SimpleObject();
        simpleObject.setId(420L); // Not right, when id is a generated value then no need to set this.
        simpleObject.setKey("Friend");
        simpleObject.setValue("Bani");

        EntityManager entityManager = EntityManagerUtil.getEntityManager();
        entityManager.getTransaction().begin();
        entityManager.persist(simpleObject);
        entityManager.getTransaction().commit();

        List<SimpleObject> simpleObjectList = entityManager.createNamedQuery("SimpleObject.findAll").getResultList();
        for(SimpleObject simple : simpleObjectList){
            System.out.println(simple);
        }

        entityManager.close();
        
    }
}

我想救它的时候，它把它扔出去了

PersistentObjectException: detached entity passed to persist.

我所需要修复的是删除主方法中simpleObject的id设置行。