我正在尝试运行这个基本的JPA/EJB代码:publicstaticvoidmain(String[]args){UserBeanuser=newUserBean();user.setId(1);user.setUserName("name1");user.setPassword("passwd1");em.persist(user);}我收到此错误:javax.ejb.EJBException:javax.persistence.PersistenceException:org.hibernate.PersistentObjectException:detachedentitypas