[hibernate-issues] [Hibernate-JIRA] Resolved: (OGM-31) ConcurrentModificationException on ArrayList representing the collection

ConcurrentModificationException on ArrayList representing the collection ------------------------------------------------------------------------- Key: OGM-31 URL: http://opensource.atlassian.com/projects/hibernate/browse/OGM-31 Project: Hibernate OGM Issue Type: Bug Components: core Reporter: Emmanuel Bernard Fix For: 3.0-next Several instances can access the collection and try and update things. Since the underlying implementation is a simple ArrayList, you can get ConcurrentModificationException if someone reads it while someone else update it. {code} Exception in thread "pool-5-thread-2" java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at org.hibernate.ogm.util.impl.PropertyMetadataProvider.findMatchingTuple(PropertyMetadataProvider.java:137) at org.hibernate.ogm.persister.Dehydrator.doRemovePropertyMetadata(Dehydrator.java:219) at org.hibernate.ogm.persister.Dehydrator.dehydrate(Dehydrator.java:140) at org.hibernate.ogm.persister.OgmEntityPersister.dehydrate(OgmEntityPersister.java:784) at org.hibernate.ogm.persister.OgmEntityPersister.update(OgmEntityPersister.java:747) at org.hibernate.action.EntityUpdateAction.execute(EntityUpdateAction.java:113) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:265) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:185) at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133) at pt.ist.fenixframework.example.bankbench.hib.HibTxSystem.doIt(HibTxSystem.java:85) at pt.ist.fenixframework.example.bankbench.TxCommand.run(TxCommand.java:14) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:680) {code} Problem: - the collection should be copied on read and that's not the case - the proper approach is to wrap it as an AtomicMap to benefit from the "diff" change - longer term, we need the merge on conflict policy in Infinispan.