Java/Hibernate: How to detect, if field is lazy-loaded proxy and not actual data?

Question

I'm converting my entity to DTO and I want to set NULL as DTO value for all fields, which are lazy-loaded and not initialized (because I do not want to transfer all the data all the time).

I've tried:

if (!(entity.getNationality() instanceof HibernateProxy))
    this.setNationalityFromEntity(entity.getNationality());

But it did not seemed to help. Any suggestions are welcome!

Thank you!

Answer 1

They way we do this in our Entities is we have boolean methods which do the check in a way that will not trigger the lazy loading. For example, if our Entity had an associated entity called 'associatedSomething', then the method to check if that associated Entity has been lazy loaded would be:

    public boolean isAssociatedSomethingLoaded() {
        if (associatedSomething instanceof HibernateProxy) {
            if (((HibernateProxy)associatedSomething).getHibernateLazyInitializer().isUninitialized()) {
                return false;
            }
        }
        return (getAssociatedSomething() != null);
    }

NOTE: It's important not to use getAssociatedSomething() in the check, as this makes sure that the associated Entity does not get lazy-loaded during the check.

Answer 2

The class is always a proxy, whether it's initialized or not, so you're going to exclude it every time if you just check for instances of proxy. The Lazy Load does not cause the Proxy reference on the entity to be replaced with a reference to a new object, it just populates the fields.

To find out if it's actually initialized you need to ask it!

if (HibernateProxy.class.isInstance(entity.getNationality())) {
  HibernateProxy proxy = HibernateProxy.class.cast(entity.getNationality());
  if (!proxy.getHibernateLazyInitializer().isUninitialized()) {
    this.setNationalityFromEntity(entity.getNationality());
  }
}