java - Hibernate:提交()后分离实体

Question

我在代码中收到了以下错误消息，尽管我从未手动调用 detach() 命令:

org.hibernate.PersistentObjectException: detached entity passed to persist: my.entity

我的实体使用持久化

try
        {
                entityManager.getTransaction().begin(); 
                entityManager.persist(item);
                entityManager.getTransaction().commit(); 
        }
        catch(final Exception e)
        {
               entityManager.getTransaction().rollback();
               LOGGER.err("Error at persist.");
               throw new Exception();
        }

在文献中，我发现javax.persistence.EntityManager在close()、EntityManager.getTransaction().commit( ) 以及序列化。(参见here)。因此，我假设每个 item 在此操作后都会自动分离。对吗？

我怀疑这是我问题的根本原因。我只想显式触发 detach()/merge() 。是否可以更改设置，以便 EntityManager.getTransaction().commit() 不会导致 detach()？

Answer 1

实体只有在关闭或清除事务时才会分离，而不是在提交时分离？! ..

Detach

The following operations clear the entire EntityManager'spersistence context and detach all managed entity objects:

*Invocation of the close method, which closes an EntityManager.

*Invocation of the clear method, which clears an EntityManager'spersistence context.

*Rolling back a transaction - either by invocationof rollback or by a commit failure.