ConcurrentModificationException due to lazy loading

hts · **Posted:** Tue Nov 16, 2004 11:22 am

Hibernate version: 2.1.6

Full stack trace of any exception that occurs:

Code:

Throwable  java.util.ConcurrentModificationException
                at org.apache.commons.collections.SequencedHashMap$OrderedIterator.next(SequencedHashMap.java:795)
                at net.sf.hibernate.util.IdentityMap.entryList(IdentityMap.java:173)
                at net.sf.hibernate.util.IdentityMap.concurrentEntries(IdentityMap.java:54)
                at net.sf.hibernate.impl.SessionImpl.preFlushEntities(SessionImpl.java:2660)
                at net.sf.hibernate.impl.SessionImpl.flushEverything(SessionImpl.java:2250)
                at net.sf.hibernate.impl.SessionImpl.autoFlushIfRequired(SessionImpl.java:1805)
                at net.sf.hibernate.impl.SessionImpl.getQueries(SessionImpl.java:1568)
                at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1533)
                at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:1521)
                at nl.linkit.projects.sfdc.db2.SynchronizedSession.find(SynchronizedSession.java:116)
                at nl.linkit.projects.sfdc.db2.MachineDaoHib.findMachineData(MachineDaoHib.java:97)
                at nl.linkit.projects.sfdc.operator.MachineSpeedChart2.initCharts(MachineSpeedChart2.java:124)
                at nl.linkit.projects.sfdc.operator.MachineSpeedChart2.init(MachineSpeedChart2.java:80)
                at nl.linkit.projects.sfdc.operator.MachineSpeedChart2.onApplicationEvent(MachineSpeedChart2.java:196)
                at org.springframework.context.event.ApplicationEventMulticasterImpl.onApplicationEvent(ApplicationEventMulticasterImpl.java:63)
                at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:188)
                at nl.linkit.projects.sfdc.operator.OperatorManager.onApplicationEvent(OperatorManager.java:118)
                at org.springframework.context.event.ApplicationEventMulticasterImpl.onApplicationEvent(ApplicationEventMulticasterImpl.java:63)
                at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:188)
                at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:271)
                at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:58)
                at nl.linkit.projects.sfdc.operator.OperatorConsole.setupApplicationContext(OperatorConsole.java:208)
                at nl.linkit.projects.sfdc.operator.OperatorConsole.startup(OperatorConsole.java:204)
                at nl.linkit.projects.sfdc.swing.ClientConsole.doMain(ClientConsole.java:48)
                at nl.linkit.projects.sfdc.operator.OperatorConsole.main(OperatorConsole.java:70) 

Name and version of the database you are using: Oracle 8.1.7

Hi there,

Above is the error thats occurs during startup of my application (1 out of every 4 times). I thought I could not run into this problem, because I am using a singleton for Hibernate access (my SynchronizedSession) and every access of the Session is using a 'synchronized' statement.

However, it turns out that my session.find() is running on the main thread and meanwhile there is some lazy loading of a collection going on in the AWT-EventQueue thread.

I have looked at the Hibernate sourcecode and it is trying to prevent the ConcurrentModificationException by 'cloning' the collection. However, it is now failing during this cloning operation (SessionImpl.preFlushEntities).

My current workaround is to disable lazy loading of all collections, but there is a major performance penalty.

Is there any other way to achieve the same thing? Or is this just the drawback of using a single Session which remains open during the entire lifespan of my Swing application?