Hi. I'm working on a content manager, and I need to execute some logic whenever an entity (a Publication) changes one of its properties (its validation state), so I'm currently building my SessionFactory with an Interceptor bound to it. The only method I'm implementing is onFlushDirty. It looks like this:



Publications, Contents and Versions are mapped like this (simplified):



As you can see, I'm using proxies and lazy initializations for lists, and despite I've put a simplified mapping configuration, the rest of it it's also pretty simple. The thing is, whenever the contentTypeTimestamped method is called, strange things begin to occur. None of my logic inside onFlushDirty performs any modification to any entity.

The strange things are, for example, that if I try to iterate the versions list later, I get a NullPointerException in the iterator() method of net.sf.hibernate.collection.Set class, since its internal "set" field is null. It doesn't happen if I'm not using the interceptor or the contentTypeTimestamped is not invoked. Another example is that, if I try to iterate over a list of associated contents twice (I didn't put it in the mapping above for sake of simplicity, but it's a simple lazy initialized many to many List), and access a simple String property of its entities, the first iteration works fine, and then on the second, Hibernate starts executing queries like crazy until I get an OutOfMemoryError.

I think it all has to do with the proxies and lazy initializations. But, even if I'm using them, I think I could safely access an entity inside onFlushDirty as long as I don't modify any entity's state. Am I wrong?

I'm using Hibernate 2.1.8, BTW.

Thanks in advance

I've just removed the proxies and lazy initializations in the Content-Version relationship, and then I don't get the NPE on the net.sf.hibernate.collection.Set class, but I get one later in another lazy initialized List, exactly on the method size() of net.sf.hibernate.collection.List. The error is basically the same, its wrapped list is null when it's trying to access it.

Both the iterator() method inside Set class and size() inside List have an invocation to read() (right before it invokes the corresponding method on the wrapped objects), which I suppose it should initialize the collections correctly, but it seems it isn't.

Why are these NPE happening on lazy initialized collections if I try to read objects with lazy initializations inside onFlushDirty?

Thanks again

I'm trying to get down to the root of the problem. It seems that the point that makes everything work or fail is the getLoadingCollection() method inside SessionImpl class. This is an extract of it:



When everyting works fine (i. e., I don't configure an Interceptor), the call to getCollection(ckey) returns a PersistentCollection object whose associated CollectionEntry is not initialized, so the collection gets initialized.

But when I'm using my Interceptor, getCollection(ckey) returns null and then, getCollectionOwner(id, persister) returns an entity whose associated EntityEntry is in LOADED status, so the method returns and no initialization is performed, and then a NullPointerException is thrown.