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silveraxe
 Post subject: Problem with TransientObjectException and Query.list
PostPosted: Tue Aug 30, 2005 9:05 am 
Newbie

Joined: Mon Aug 29, 2005 5:21 am
Posts: 9
I have a problem with querying some objects and creating a list of these objects. I sometimes get a "TransientObjectException" in the following code and can't reproduce the problem and do not really understand why the exception is thrown.

The Exception tells me "object references an unsaved transient instance - save the transient instance before flushing: de.pgew.netstructure.Controlunit" but I only query the database so it does not make sense to save anything.

I hope anybody can help me with this problem. If further information is necessary I will post it here.

Code:
// create connection
Session session=HibernateUtil.currentSession();
Transaction tx=session.beginTransaction();

// read devices
Query q=session.createQuery("from Device device where device.devicetype='splitter'");
Device[] splitters=(Device[])q.list().toArray(new Device[]{});

// close connection
tx.commit();
HibernateUtil.closeSession();



Hibernate version:
3

Mapping documents:
Code:
// Only part of the document
<class name="de.pgew.netstructure.Device" table="netstructure_device">
  <id name="id" type="java.lang.Integer">
    <column name="id" length="11" not-null="true" unique="true" sql-type="int" />
    <generator class="native">
      <param name="sequence">netstructure_device_sequence</param>
    </generator>
  </id>
   
  <property name="devicetype" type="java.lang.String">
    <column name="devicetype" length="9" not-null="true" sql-type="enum" />
  </property>

  <property name="voltage" type="java.lang.String">
    <column name="voltage" length="11" not-null="false" sql-type="enum" />
  </property>

  <property name="location" type="java.lang.String">
    <column name="location" length="200" not-null="true" sql-type="varchar" />
  </property>

  <property name="externalID" type="java.lang.String">
    <column name="externalID" length="200" not-null="false" sql-type="varchar" />
  </property>

  <many-to-one name="controlunit" column="controlunit" not-null="true"/>

  <set name="cables" inverse="true">
    <key column="id"/>
    <one-to-many class="de.pgew.netstructure.Cable"/>
  </set>
</class>

<class name="de.pgew.netstructure.Controlunit" table="netstructure_controlunit" lazy="false">
  <id name="Id" type="java.lang.Integer">
    <column name="id" length="11" not-null="true" unique="true" sql-type="int" />
    <generator class="native">
      <param name="sequence">netstructure_cunit_sequence</param>
    </generator>
  </id>
   
  <property name="externalID" type="java.lang.String">
    <column name="externalID" length="11" not-null="true" sql-type="varchar" />
  </property>   

  <set name="devices" inverse="true">
    <key column="id"/>
    <one-to-many class="de.pgew.netstructure.Device"/>
  </set>
   
</class>



Full stack trace of any exception that occurs:
Code:
-> Exception org.hibernate.TransientObjectException occured
org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:216)
org.hibernate.type.EntityType.getIdentifier(EntityType.java:99)
org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:63)
org.hibernate.persister.entity.BasicEntityPersister.dehydrate(BasicEntityPersister.java:1617)
org.hibernate.persister.entity.BasicEntityPersister.update(BasicEntityPersister.java:1963)
org.hibernate.persister.entity.BasicEntityPersister.updateOrInsert(BasicEntityPersister.java:1909)
org.hibernate.persister.entity.BasicEntityPersister.update(BasicEntityPersister.java:2149)
org.hibernate.action.EntityUpdateAction.execute(EntityUpdateAction.java:75)
org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223)
org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:137)
org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)
org.hibernate.event.def.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:48)
org.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:711)
org.hibernate.impl.SessionImpl.prepareQueries(SessionImpl.java:895)
org.hibernate.impl.SessionImpl.getQueries(SessionImpl.java:885)
org.hibernate.impl.SessionImpl.list(SessionImpl.java:834)
org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
de.pgew.netstructure.NetStructureDevice.getAllSplitters(NetStructureDevice.java:347)
...


Name and version of the database you are using:
Oracle 9i[/code]
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steckemetz
 Post subject:
PostPosted: Tue Aug 30, 2005 9:29 am 
Pro
Pro

Joined: Mon Jan 24, 2005 5:39 am
Posts: 216
Location: Germany
Hi,

I am certainly not an expert.
Its a matter of the FlushMode.
Usually its Auto meaning:

Quote:
/**
* The <tt>Session</tt> is sometimes flushed before query execution
* in order to ensure that queries never return stale state. This
* is the default flush mode.
*/


So if you execute your query, your objects
are flushed to db indicate by the line

Quote:
org.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:711)

in your stacktrace. And since you reference
transient objects you get that exception.

hope this helps.
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silveraxe
 Post subject:
PostPosted: Tue Aug 30, 2005 10:40 am 
Newbie

Joined: Mon Aug 29, 2005 5:21 am
Posts: 9
Thank you for your answer. This seems really to be the problem and explains why the Exception is not always thrown. I changed the source code to the following and hope it will work now:

Code:
// create connection
Session session=HibernateUtil.currentSession();
FlushMode oldFM=session.getFlushMode();
Transaction tx=session.beginTransaction();
Transaction tx=session.beginTransaction();

// read devices
Query q=session.createQuery("from Device device where device.devicetype='splitter'");
Device[] splitters=(Device[])q.list().toArray(new Device[]{});

// close connection
tx.commit();
session.setFlushMode(oldFM);
HibernateUtil.closeSession();


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silveraxe
 Post subject:
PostPosted: Tue Aug 30, 2005 10:41 am 
Newbie

Joined: Mon Aug 29, 2005 5:21 am
Posts: 9
I wanted to post this:
Code:
// create connection
Session session=HibernateUtil.currentSession();
FlushMode oldFM=session.getFlushMode();
session.setFlushMode(FlushMode.NEVER);
Transaction tx=session.beginTransaction();

// read devices
Query q=session.createQuery("from Device device where device.devicetype='splitter'");
Device[] splitters=(Device[])q.list().toArray(new Device[]{});

// close connection
tx.commit();
session.setFlushMode(oldFM);
HibernateUtil.closeSession();


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