how to write new entity in postCalculateUnitOfWorkChangeSet or preCommitTransaction

Question

I am using Eclipselink and want to write changlog (an entity) for all insert/change/delete business enitities. I found the hooks postCalculateUnitOfWorkChangeSet or preCommitTransaction of SessionEventAdapter where I can build and insert changelog basing on the changeset. How can I get the changeset for insert/update/delete object in the two methods? How can I insert new changelog entities with the same unit of work because I need they happen in the same transaction.

What I tried is as below:

@Override
    public void postCalculateUnitOfWorkChangeSet(SessionEvent event) {
        Object source = event.getSource();
        if (source instanceof UnitOfWork) {
            UnitOfWork unitOfWork = (UnitOfWork) source;
            UnitOfWorkChangeSet unitOfWorkChangeSet = unitOfWork.getUnitOfWorkChangeSet();
            if (unitOfWorkChangeSet != null && unitOfWorkChangeSet.hasChanges()) {
                Map allChangeSets = unitOfWorkChangeSet.getAllChangeSets();
                allChangeSets.forEach((k, v) -> {
                            if (v instanceof ObjectChangeSet) {
                                ObjectChangeSet ocs = (ObjectChangeSet) v;
                                if (ocs.isNew()) {
                                    Object unitOfWorkClone = ocs.getUnitOfWorkClone();
                                    if (unitOfWorkClone instanceof Traceable) {
                                        ChangeLog changeLog = getChangeLog(Operation.INSERT, (Traceable) unitOfWorkClone);
                                        unitOfWork.registerNewObject(changeLog);
                                        unitOfWork.getParent().insertObject(changeLog);
                                    }
                                } else {
                                    List<ChangeRecord> changes = ((ObjectChangeSet) v).getChanges();
                                    changes.forEach(c -> {
                                        Object unitOfWorkClone = ((ObjectChangeSet) (c.getOwner())).getUnitOfWorkClone();
                                        if (unitOfWorkClone instanceof Traceable) {
                                            ChangeLog changeLog = getChangeLog(Operation.UPDATE, (Traceable) unitOfWorkClone);
                                            unitOfWork.getParent().insertObject(changeLog);
                                        }
                                    });
                                }
                            }
                        }
                );
            }

        }

    }

This can work but : 1. I am not sure if it is right way to get the changeset because I did not find document on this. 2. It cannot batch write. When I batch insert business objects, the business obejcts can be written in batch. But the changelogs are inserted one by one.

I also tried history policy. but it cannot work well with batch write. eclipselink batch write is disabled when use history policy or DescriptorEventAdapter

Thanks a lot for your any comments.