[原]Hibernate - TransientObjectException

[标题]:[原]Hibernate - TransientObjectException
[时间]:2009-6-19
[摘要]:object references an unsaved transient instance
[关键字]:Hibernate，
[环境]:Hibernate3.2，MyEclipse7.0，MySQL5.1
[作者]:Winty ([e-mail]) http://www.blogjava.net/wintys

[错误]:

ERROR AbstractFlushingEventListener:301 - Could not synchronize database state with session
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: wintys.hibernate.manytomany.Course
    at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:219)
    at org.hibernate.type.EntityType.getIdentifier(EntityType.java:397)
    at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:78)
    at org.hibernate.persister.collection.AbstractCollectionPersister.writeElement(AbstractCollectionPersister.java:755)
    at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1143)
    at org.hibernate.action.CollectionRecreateAction.execute(CollectionRecreateAction.java:26)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:250)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:234)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:145)
    at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:298)
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000)
    at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:338)
    at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
    at wintys.hibernate.manytomany.StudentDAOBean.insert(StudentDAOBean.java:49)
    at org.apache.jsp.index_jsp._jspService(index_jsp.java:68)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Unknown Source)
object references an unsaved transient instance - save the transient instance before flushing: wintys.hibernate.manytomany.Course

[原因]:
    使用session.save时，相关的级联对象没有被保存。

[解决]:
Either use session.save for both objects or specify a cascade="save-update,persist" in your mapping.
即:
1、加上cascade="all"
<set name="courses" table="student_course" cascade="all">
...
</set>
程序中直接使用。
session.save(student);

2、修改程序，使相关的级联对象先保存。
session.save(course);//加上这一句
session.save(student);//student中关联了course

[参考资料]:
object references an unsaved transient instance - save the transient instance before flushing : http://blog.csdn.net/riseman/archive/2008/03/03/2143661.aspx

原创作品，转载请注明出处。
作者:Winty ([e-mail])
博客:http://www.blogjava.net/wintys