Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: com.test.usermanage.model.User
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1387)at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1310)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1316)
at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:881)
at com.test.usermanage.test.ClientEntity.main(ClientEntity.java:27)
Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist: com.test.usermanage.model.User
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:141)
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:78)
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:852)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:826)
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:830)
at org.hibernate.ejb.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:875)
... 1 more
User user = new User();
user.setId(2);
改：
User user = new User();
user.setId(null);