Converting Hibernate proxy to real entity object

Question

During Hibernate session I am loading some objects and some of them are loaded as proxies due to lazy loading. It's all OK and I don't want to turn lazy loading off.

But later I need to send some of the objects (actually one object) to the GWT client via RPC. And it happens that this concrete object is a proxy. So I need to turn it to real object. I can't find a method like "materialize" in Hibernate.

How can I turn some of the objects from proxies to reals knowing their class and ID?

At the moment the only solution I see is to evict that object from Hibernate's cache and reload it, but it is really bad for many reasons.

Answer 1

The way I recommend with JPA 2 :

Object unproxied  = entityManager.unwrap(SessionImplementor.class).getPersistenceContext().unproxy(proxy);

Answer 2

I found a solution to deproxy a class using standard Java and JPA API. Tested with hibernate, but does not require hibernate as a dependency and should work with all JPA providers.

Onle one requirement - its necessary to modify parent class (Address) and add a simple helper method.

General idea: add helper method to parent class which returns itself. when method called on proxy, it will forward the call to real instance and return this real instance.

Implementation is a little bit more complex, as hibernate recognizes that proxied class returns itself and still returns proxy instead of real instance. Workaround is to wrap returned instance into a simple wrapper class, which has different class type than the real instance.

In code:

class Address {
   public AddressWrapper getWrappedSelf() {
       return new AddressWrapper(this);
   }
...
}

class AddressWrapper {
    private Address wrappedAddress;
...
}

To cast Address proxy to real subclass, use following:

Address address = dao.getSomeAddress(...);
Address deproxiedAddress = address.getWrappedSelf().getWrappedAddress();
if (deproxiedAddress instanceof WorkAddress) {
WorkAddress workAddress = (WorkAddress)deproxiedAddress;
}

Answer 3

Try to use Hibernate.getClass(obj)

Answer 4

With Spring Data JPA and Hibernate, I was using subinterfaces of JpaRepository to look up objects belonging to a type hierarchy that was mapped using the "join" strategy. Unfortunately, the queries were returning proxies of the base type instead of instances of the expected concrete types. This prevented me from casting the results to the correct types. Like you, I came here looking for an effective way to get my entites unproxied.

Vlad has the right idea for unproxying these results; Yannis provides a little more detail. Adding to their answers, here's the rest of what you might be looking for:

The following code provides an easy way to unproxy your proxied entities:

import org.hibernate.engine.spi.PersistenceContext;
import org.hibernate.engine.spi.SessionImplementor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.repository.JpaContext;
import org.springframework.stereotype.Component;

@Component
public final class JpaHibernateUtil {

    private static JpaContext jpaContext;

    @Autowired
    JpaHibernateUtil(JpaContext jpaContext) {
        JpaHibernateUtil.jpaContext = jpaContext;
    }

    public static <Type> Type unproxy(Type proxied, Class<Type> type) {
        PersistenceContext persistenceContext =
            jpaContext
            .getEntityManagerByManagedType(type)
            .unwrap(SessionImplementor.class)
            .getPersistenceContext();
        Type unproxied = (Type) persistenceContext.unproxyAndReassociate(proxied);
        return unproxied;
    }

}

You can pass either unproxied entites or proxied entities to the unproxy method. If they are already unproxied, they'll simply be returned. Otherwise, they'll get unproxied and returned.

Hope this helps!