此错误是我在写hibernate一对一外唯一外键关联映射（单项关联）时出错，我如果向主键表插入记录是正确的，可在插入有外键表时就要出现下列异常，希望那位知道的朋友给我说解决一下，谢谢～～～
Exception in thread "main" org.hibernate.PropertyValueException: not-null property references a null or transient value: org.qin.hiberanteDome7.TU.tg
 at org.hibernate.engine.Nullability.checkNullability(Nullability.java:72)
 at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:265)
 at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:167)
 at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:101)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)
 at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)
 at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
 at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
 at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:530)
 at org.hibernate.impl.SessionImpl.save(SessionImpl.java:518)
 at org.hibernate.impl.SessionImpl.save(SessionImpl.java:514)
 at org.qin.hiberanteDome7.Tu_Tg_Oprate.main(Tu_Tg_Oprate.java:44)