How to retrieve the audited revision of relations?

Question

Here is my use case

I have two entities : Personn and Email (a @OneToMany relation). Both of them are audited.

First I create a new Personn, with an Email (=> Both of them have a revision 1), then I modify the Email (=> The Email has a revision 2, but Personn has only a revision 1)

In the web application the end-user has only one view to show the Personn's attributs and also his Emails attributs. In this view I want to show all existing revisions for this Personn. But when I query the audit system, it doesn't show me revision 2 as the Personn has not been modified.

I understand the technical problem, but in the end-user point of view, he wants to see a revision 2 because he modified the personn's email ! He doesn't know (and doesn't have to know) that we deciced to divide these information into 2 Java objects. Of course this problem is not only for Personn-Email relation (I've got a lot of relation between Personn and other objects which are shown in the same view - Adress, Job, Site, Card, and many more)

I thought about 2 solutions:

1- Querying all relations to know if a Revision exist (but I suppose it will generate a big request or multiple requests - I've got a lot of relations).

2- Setting "hibernate.listeners.envers.autoRegister" to false, writing my own EnversIntegrator and event implementations. In event implementations (which override default Envers implementations), I will create a ModWorkUnit for Personn when Email's attributs have been modified (it will not been hard coded of course: perharps a custom annotation like @AuditedPropagation on the personn field). The flaw of this solution is to create a lot a row for Personn even if it was not modified.

What do you think about these solutions ? Do you know a better way to solve that kind of use-case ?

Thanks for your advices.

Answer 1

I tried to implement the second solution:

1. First my integrator which adds a new post update listener (RevisionOnCollectionPostUpdateEventListenerImpl)

   public class RevisionOnCollectionUpdateIntegrator implements Integrator {
   private static final CoreMessageLogger LOG = Logger.getMessageLogger(CoreMessageLogger.class, RevisionOnCollectionUpdateIntegrator.class.getName());
   
   public static final String REGISTER_ON_UPDATE = "org.hibernate.envers.revision_on_collection_update";
   
   @Override
   public void integrate(Configuration configuration, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
   
       final boolean autoRegister = ConfigurationHelper.getBoolean(REGISTER_ON_UPDATE, configuration.getProperties(), true);
       if (!autoRegister) {
           LOG.debug("Skipping 'revision_on_collection_update' listener auto registration");
           return;
       }
   
       EventListenerRegistry listenerRegistry = serviceRegistry.getService(EventListenerRegistry.class);
       listenerRegistry.addDuplicationStrategy(EnversListenerDuplicationStrategy.INSTANCE);
   
       final AuditConfiguration enversConfiguration = AuditConfiguration.getFor(configuration, serviceRegistry.getService(ClassLoaderService.class));
       if (enversConfiguration.getEntCfg().hasAuditedEntities()) {
           listenerRegistry.appendListeners(EventType.POST_UPDATE, new RevisionOnCollectionPostUpdateEventListenerImpl(enversConfiguration));
       }
   }
   

2. And then the post update listener (which extends):

   public class RevisionOnCollectionPostUpdateEventListenerImpl extends EnversPostUpdateEventListenerImpl {
   protected final void generateBidirectionalWorkUnits(AuditProcess auditProcess, EntityPersister entityPersister, String entityName, Object[] newState,
           Object[] oldState, SessionImplementor session) {
       // Checking if this is enabled in configuration ...
       if (!getAuditConfiguration().getGlobalCfg().isGenerateRevisionsForCollections()) {
           return;
       }
   
       // Checks every property of the entity, if it is an "owned" to-one relation to another entity.
       // If the value of that property changed, and the relation is bi-directional, a new revision
       // for the related entity is generated.
       String[] propertyNames = entityPersister.getPropertyNames();
   
       for (int i = 0; i < propertyNames.length; i++) {
           String propertyName = propertyNames[i];
           RelationDescription relDesc = getAuditConfiguration().getEntCfg().getRelationDescription(entityName, propertyName);
           if (relDesc != null && relDesc.isBidirectional() && relDesc.getRelationType() == RelationType.TO_ONE && relDesc.isInsertable()) {
               // Checking for changes
               Object oldValue = oldState == null ? null : oldState[i];
               Object newValue = newState == null ? null : newState[i];
   
                       // Here is the magic part !!!!!!!!!
                       // The super class verify if old and new value (of the owner value) are equals or not
                       // If different (add or delete) then an audit entry is also added for the owned entity
                       // When commented, an audit row for the owned entity is added when a related entity is updated
           //  if (!Tools.entitiesEqual(session, relDesc.getToEntityName(), oldValue, newValue)) {
                   // We have to generate changes both in the old collection (size decreses) and new collection
                   // (size increases).
                   if (newValue != null) {
                       addCollectionChangeWorkUnit(auditProcess, session, entityName, relDesc, newValue);
                   }
   
                   if (oldValue != null) {
                       addCollectionChangeWorkUnit(auditProcess, session, entityName, relDesc, oldValue);
                   }
           //  }
           }
       }
   }
   

It seems to work but I have to test a little bit more.

Answer 2

I have been unable to make the custom post update listener solution work. addCollectionChangeWorkUnit doesn't seem to exist until hibernate 4.1 where it is marked private. EnversPostUpdateEventListenerImpl seems to appear at some point in hibernate 4.0

I solved my problem by adding a hidden lastUpdated date field on my equivalent of your A entity.

@Entity
public class A {
    private Date lastModified;
    @OneToMany(mappedBy = "a", cascade = CascadeType.ALL )
    private List<B> blist;
    public void touch(){
        lastModified=new Date();
    }
}

In the related entities (like you B field), I added the following :

public class B {
    @ManyToOne
    private A a; 

    @PreUpdate
    public void ensureParentUpdated(){
        if(a!=null){
            a.touch();
        }
    }
}

This ensures that a revision is added to A whenever a revision is added to B even though it requires custom code in many entities.