Hibernate中实体的三种状态

刚刚查看了一下Hibernate的DOC，发现里面也讲到了Hibernate实体的三种状态，下面是官方的解释：

ThemainfunctionoftheSessionistooffercreate,readanddeleteoperationsforinstancesofmappedentityclasses.Instancesmayexistinoneofthreestates:

transient:neverpersistent,notassociatedwithanySession

persistent:associatedwithauniqueSession

detached:previouslypersistent,notassociatedwithanySession

Transientinstancesmaybemadepersistentbycallingsave(),persist()orsaveOrUpdate().Persistentinstancesmaybemadetransientbycallingdelete().Anyinstancereturnedbyaget()orload()methodispersistent.Detachedinstancesmaybemadepersistentbycallingupdate(),saveOrUpdate(),lock()orreplicate().Thestateofatransientordetachedinstancemayalsobemadepersistentasanewpersistentinstancebycallingmerge().

save()andpersist()resultinanSQLINSERT,delete()inanSQLDELETEandupdate()ormerge()inanSQLUPDATE.ChangestopersistentinstancesaredetectedatflushtimeandalsoresultinanSQLUPDATE.saveOrUpdate()andreplicate()resultineitheranINSERToranUPDATE.

Itisnotintendedthatimplementorsbethreadsafe.Insteadeachthread/transactionshouldobtainitsowninstancefromaSessionFactory.

ASessioninstanceisserializableifitspersistentclassesareserializable.

Atypicaltransactionshouldusethefollowingidiom:

Sessionsess=factory.openSession();

Transactiontx;

try{

tx=sess.beginTransaction();

//dosomework

...

tx.commit();

}

catch(Exceptione){

if(tx!=null)tx.rollback();

throwe;

}

finally{

sess.close();

}

IftheSessionthrowsanexception,thetransactionmustberolledbackandthesessiondiscarded.TheinternalstateoftheSessionmightnotbeconsistentwiththedatabaseaftertheexceptionoccurs.

关于这三种状态，网上已经有很多解释，不过我觉得还是看官方的权威