org.hibernate.AssertionFailure: no queued adds
Getting above exception while flush

Use case – In our application, before doing any logical operation we persist whole state of statefull EJB including session to file or in memory byte [], and we restore this state if we encounter any exception. In this particular case I have performed following steps.
1. Fetch an object which has a list (size>0, lazy = true) in it.
2. Add another object in this list.
3. Serialize session.
4. Restore session.
5. Try to call flush on session, and we get the following exception.
Exception in thread "main" org.hibernate.AssertionFailure: no queued adds
at org.hibernate.action.CollectionUpdateAction.execute(CollectionUpdateAction.java:67)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:260)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:182)
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:1206)
at Main.main(Main.java:46)

This problem comes because of usage of bag and transient variable (transient List operationQueue) in AbstractPersistentCollection class of hibernate. Bag doesn’t get initialized when object is added to it; instead this object gets added to operationQueue List which is transient so when we restore it back previous value is lost.

Solution –
1. Eagerly load collection (lazy = false)
2. Use set instead of bag

Please suggest me any other solution for solving this problem. Why operationQueue object transient?

We have the same problem with Spring WebFlow and Hibernate. A PersistentBag is created by Hibernate and does not fully survive serial/deserialization by WebFlow. It loses some of its state and leads to the "no queued adds" exception.

We replaced the bag with a new implementation of a list (copying the bag's contents into the new list) and this seemed to workaround the issue.

A pure Webflow solution is to switch off snapshots - if it can be tolerated.

We're not quite sure why some of the Bag's attributes are marked with the transient modifier, but think it may be for performance reasons?

We had the same issue with Hibernate and Spring Web Flow when adding a new child to a list in the parent entity.

There are two easier workarounds,
1) use a Hibernate User Type to override the default PersistentBag implementation of the list.
Apply @org.hibernate.annotations.Type(type="org.hibernate.collection.PersistentList") on top of @OneToMany

2) save/merge the parent object instead of the transient child.
parent.getChildren().add(0, transientChild);
entityManager.merge(parent); // cascade save

Note the funny syntax on the line, parent.getChildren().add(0, transientChild); this is to solve a defect in Hibernate reported here, https://hibernate.onjira.com/browse/HHH-5855.