Problem loading subclasses of hibernate entity

Question

I have an en Entity A which is super class for entities B and C, A is annotated with @Inheritance(strategy = InheritanceType.JOINED).

Then another Entity X which has relation to A.

I set x.a with some object of type B, but when I load x, and check type for x.a it is A, and I cannot cast it to B.

I did that a lot of mapping like this before and it was working correctly cannot know what is the problem here.

Also when I do entityManager.find(A.class, id), it also return A although there is an entity B with the same id, it returns B when I run it from Junit test but not when run the application on tomcat server.

Give us some code to analyze. – JB Nizet Aug 14 '11 at 15:38 — JB Nizet, Aug 14 '11 at 15:38

score 1 · Answer 1 · edited May 23 '17 at 12:26

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Sounds like you may be getting a proxy instead of the actual instance which is why you can't cast to the subclass. The following may help you unwrap the proxy:

Converting Hibernate proxy to real object

edited May 23 '17 at 12:26

Community

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answered Aug 15 '11 at 04:10

Abdullah Jibaly

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score 0 · Answer 2 · edited May 23 '17 at 10:25

You will encounter this problem in connection with the lazy-loading mechanism of Hibernate. Hibernate wraps each object that is lazily loaded into a so-called proxy object. Your object x.a will be of type HibernateProxy, when you load x from database.

I've found this solution useful (similar to @Abdullah's).

How to unproxy a hibernate object

You could also eagerly fetch the relation x.a to avoid this problem, hence there won't be a proxy-object created.

Problem loading subclasses of hibernate entity

2 Answers2