在JPA中，有什么方法可以复制Hibernate的saveOrUpdate行为，

saveOrUpdate

public void saveOrUpdate(Object object)
                  throws HibernateException

    Either save(Object) or update(Object) the given instance, depending upon resolution of the unsaved-value checks (see the manual for discussion of unsaved-value checking).

    This operation cascades to associated instances if the association is mapped with cascade="save-update".

    Parameters:
        object - a transient or detached instance containing new or updated state 
    Throws:
        HibernateException
    See Also:
        save(Object), update(Object)

它实质上检查数据库中是否已存在该对象，并根据需要更新该对象或保存该对象的新实例。

JPA无事务读取很不错，但是Hibernate确实缺少这种方法。有经验的JPA开发人员如何处理此问题？