Hi,

I'm writing a Swing gui. We have a search screen that runs a query in hibernate. The search is paginated and we use a SwingWorker. The first chunk of data comes in and we give it to the gui to display. This involves a jump onto the Event Dispatch Thread (EDT). The gui may require associations to be lazy loaded. We now have two threads accessing the same session, the 'search thread' and the EDT.

I can't think of a solution to solve this that preserves :
* not locking the gui when we do a search.
* not explicitly hydrating all associations needed for the gui to display.

does anyone have any ideas on how to solve this?
are there thread safe session implementations that we could use? Does it make sense to write one?

thanks, Don
ps. the stacktraces I'm getting are :

java.util.ConcurrentModificationException
at org.apache.commons.collections.SequencedHashMap$OrderedIterator.next(SequencedHashMap.java:757)
at org.hibernate.engine.StatefulPersistenceContext.afterTransactionCompletion(StatefulPersistenceContext.java:289)
at org.hibernate.impl.SessionImpl.afterTransactionCompletion(SessionImpl.java:444)
at org.hibernate.jdbc.JDBCContext.afterNontransactionalQuery(JDBCContext.java:224)
at org.hibernate.impl.SessionImpl.afterOperation(SessionImpl.java:437)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1134)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
at org.springframework.orm.hibernate3.HibernateTemplate$29.doInHibernate(HibernateTemplate.java:807)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:356)
at org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:798)
at org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:794)
at it.orchestrate.oep.territory.hibernate.TerritoryDAOImpl.findAccountsForTerritories(TerritoryDAOImpl.java:46)
at it.orchestrate.oep.territory.TerritoryManagerImpl.findAccountsForTerritories(TerritoryManagerImpl.java:207)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:292)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:155)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:122)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at it.orchestrate.oep.util.SessionInterceptor.invoke(SessionInterceptor.java:42)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
at org.springframework.aop.interceptor.AbstractTraceInterceptor.invoke(AbstractTraceInterceptor.java:97)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:174)
at $Proxy10.findAccountsForTerritories(Unknown Source)
at it.orchestrate.oba.callplanning.LocationQuery.createCriteria(LocationQuery.java:67)
at it.orchestrate.oba.callplanning.LocationQuery.execute(LocationQuery.java:40)
at it.orchestrate.oba.searchview.SearchViewWorker.doInBackground(SearchViewWorker.java:75)
at it.orchestrate.oba.searchview.SearchViewWorker.doInBackground(SearchViewWorker.java:19)
at org.jdesktop.swingworker.SwingWorker$1.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269)
at java.util.concurrent.FutureTask.run(FutureTask.java:123)
at org.jdesktop.swingworker.SwingWorker.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at java.lang.Thread.run(Thread.java:595)

From your description I am guessing you are populating the data structure (probably a collection) with Hibernate that you are also trying to display in your GUI?

I will make a further guess and say you are probably trying to iterate over your collection while changing the collection which is where the ConcurrentModificationException is coming from.

You could fix this with synchronized blocks. However, because iterating over the collection could take be expensive depending on the size of the collection (and you wouldn't want to block the collection the whole time you are interating over it) you may be better off cloning the collection when you want to display it and iterate over the clone.

This is probably more of a general Swing question than a Hibernate question.